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TECHNICAL REPORT69-28-ES

ENVIRONMENTAL CONDITIONS RELATING TOHARMFUL INSECTS OF MAINLAND SOUTHEAST ASIA

by

Edgar Bingham

Geography Division

Best Available CopyProject Refer .ce: Series:ITO62109A129 ES-40

October 1968

Earth Sciences LaboratoryU.S. ARMY NATICK LABORATORIES

Natick, Massachusetts 01760

FORVWM1UD

This report iv designeZ primarily f£r non-special.its in entomoiogicalscience who require a ready source of information on the disease-carryinginsects and other arthropods of Southeast Asia and their ecolagital affi-i-ties. It shows., by graphic and tabular means, in what types of t=rrAiu agiven species may be expected, considering such factors as %agetation,surface water, elevation, and hmen population density. Tbus the hazardto troops and other persounel, requiring the use of special protectivemeasures, can be estimated on a aore local basts than the mere presen'.e ora species within a country.

The information in this report is derived fram secondary sources.Much of the basic information was compiled by Dr. B.V. Travis and hisascociates at Cornell University under a series of contracts sponsored bythe Office of the Chief of Research and Development. Other open soarceswere also used, and the cooperation of the staffs of the National MedicalLibrary at Bethesda, Maryland, the University of Maryland LiSrary, and theUniversity of Virginia Library is acknowiledged with appreciation. Appre-ciation is also expressed to LTC J.E. Scanlon, Walter Reed Army Instituteof Research; to Dr. Alan Stone, Agr..cultural Research Service, U.S. De 'lt-ment of Agriculture; to Dr. 1.E. Rozeboom, Jotbs Hopkins University; and toDr. Ralph A. Brm of the Southeast Asia Mosquito Project, SmithsonianInstitutiorn, all of whom offered helpful suggeations in the preparation ofthis report.

The author is Professor of Geography at Emory and Henry College, Emory,Virginia, and during preparation of this report was employed by the EarthSciences Le satory. The physiographic cross-sections were drawn by theauthor, and the other graphic material was prepared by the CartographyOffice, Earth Sciences Laboratory, under the direction of Aubrey Greenwald, Jr.The research was conducted under Project 1T062109A129.

iii

____ ___ ___ ___ ___ ___ _ _ ____ ___ ___ ____ ___ ___ ___

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cList of Figures ov

1. Introduction 1

2. Physical Environment 1

a. Terrain Ib. ClimAte 3c. Vegetation 6d. Groind Conditions 13

S3. Harmful Arthropods 15t

a. General 15b. Mosquitoe- 15c. don-biting Fliee 16d. Fleas 17e. Sandflies 17f. Lice 17g Mites 18Sh. Ticks 18

Si. Other Arthropods 18

4. Cultural Environments and Associated HArmful Arthropods 19

Sa. Cities and Large Towns 19b. Villages and Isolated Rural Settlements 19c. Ricefields 20

5. Natural Environments and Associated Harmful Arthropois 20

a. Brackish C-'ataI Margins 20b. Delta P.airs, Coastal Plains, and Flood Plains 21c. Elevated Plains, Low Plateaus, and Foothflls 21d. Hills, Wý!rntsiau and Dissected Plateaus 22

6. Selected Bibliography 39

Appendix 45

I..

I iii

LIST OF FIGURES

ViSire No, Pale

1. Mainland Southeast Asia vi

2. Physical regions 2

3a. Average precipitation and prevailing surface windsduring June, July, and August 4

3b. Average precipitation and prevailing surface windsduring December, January, and February 5

4. Vegetation 7

5. Forest profile from humid evergreen forest to semi-arid thorn forest 10

6. Vegetational cross-section through a river valleyin the Korat Plateau 14

7. Physiographic cross-sectlon through central Burmashowing vegetation and harmful insects 23

8a. Physiographic cross-section extending east and Vestthrough central Thailand showing vegetation andharmful insects 25

8b. Physiographic cross-section extending north andsoLth through central Thailand showing vegetationand harmful insects 27

9. Physiogravhic cross-section through Cambodia andSouth Vietnam showing vegetation and harmful insects 29

10. Physiographic cross-section through southern Laosand northern South Vietnam showing vegetation andharmful insects 31

14la. Physiographic cross-section through northern La~sand North Vietnam showing vegetation and harmfulinsects 331

llb. Physiographic cross-section through northern Laos

and North Vietnam showing vegetation and harmfularthropod species 35

iv

ABSTRACT

-* Thit study illustrates the relationships between physical and cultural"environments and the presence of harmful insects and other arthropods inmainland Southeast Asia. These relationships are graphically portrayed indigraiatic cross-sections through various parts of the study area. Inaddition, the physical and cultural factors that contribute to the pro-pagation and spread of harmfu insects are analyzed, and there are briefdescriptions of the offending species.

Of the insects th*.t contribute most to the origin and ead of disease,the mosquito easily tatkes first place. The hot, humid c' ace of SoutheastAsia and the numerous water bodies provide ideal condit•jns for the survivalof this group of insects. Various mosquito species are known to be trans-mitters of malaria, dengue fever, filariasis, and Japanese B encephalitis.Other important disease-causing insects include non-biting flies, fleas,sandflies, and lice, while disease-carrying species are also found among themites and ticks. They are responsible for the spread of a wide variety ofdiseases and infections, including myiasis, plague, typhus, kala azar, yaws,and bacterial ejsentery.

The principal environmental types in Southeast Asia are: (1) citiesand large towns; (2) villages and isolated rural settlements; (3) ricefields;(4) brackish coastal margins; (5) delta plains, coastal plains, and flood-plains; (6) elevated plains, low plateaus, and foothills; and (7) hills,mountains, aue dissected plateaus. Each of these environments has its owncomplex of harmful insects. In general, the areas of lowest elevation,highest rainfall, and least population have the widest variety of harmfulinsects, and the areas of highest elevation, lowest rainfall, and densestpopulation have the fewest. However, there are exceptions to this rule.

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ENVIROIWNTAL CONDITIONS RELATING TO HARMFUL.INSECTS OF IMA32LAND SOUTHEAST ASIA

1. Introduction

The distribution of harmful insects aud other arthropods in SoutheastAsia is influenced both by the natural environment and by cultural factorsassociated with the human population of the region. Climate is the mostimportant physlcal element because of its direct effects on insect lifeand its strong relationships with natural vegetation and soil, which arealso significant determinants of insect fauna. Landforms and land-waterdisvzibution are other physical factors that influence the pattern ofins..ect life, both in terms of direct effects and their local modificationof climate.

Numerous cultural factors also influence the distribution of harr-fulinsects. Land-use patterns, rural settlements. urbanization, and popula-tion densities are reflected in ways that favcr the development and spreadof certain insects and retard or restrict development of others. The rela-tive development of public and private sanItation, the state of medical"technology, and the use of insecticides or other anti-insect measures alsohave bearing on the incidence of harmful insects.

2. Physical Environment

a. Terrain

The terrain pattern of mainland Southeast Asia has been aptly des-cribed as resembling a huge fan spreading southward from the eastern end£ of the Tibetan Upland. The ribs of the fan consist of mountain ranges,high and closely spaced in the north, somewhat lower and flaring outwardin the south. The veins of the fan are formed by the deep valleys of themajor rivers, tha Irrawaddy, the Salween, the Mekong, the Red, and otherlesser streams. As the valleys approach the sea they become wider andflatter. In their lower courses the valley floors are covered by alluviumfrom periodic floods, and the rivers are actively constructing deltas attheir points of entry into tb: sea. This arrangement of mountain chainsand valleys is the product c-s erosion and deposition by the major riversof the area. These streama have cut the high ground into elongated sectionsand have built up the lower areas ir.to their present alluvial plains.

The terrain of Southeast Asia is illustrated in Figure 2. In additionto the principal features of generally north-south trending mountain rangea3and river valleys, Southeast Asia has two major plateaus ano a structuralbasin. The highest of the plateaus is the Shan Highland, a 20,000-square-

mile upland between the Irravaddy and Salween valleys in northeastern A

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Burma. Elevations in this very rugged area range between 2800 and 5000feet. Somewhat lower in elevation and slightly smaller is the KoratPlateau, a tableland with an average elevation of about 500 feet at itscenter, rising to about 2000 feet along its southern and western rims.The basin is referred to as the Cambcdian Saucer a gentle depressionoccupying the northwestern third of the Mekong Lowland and encompassingmost of Cambodia.

A large, fresh-water lake, the Tonle Sap, covers the lowest part ofthe basin. One of the most unusual features of the physical geography ofSoutheast Asia is the yearly flooding of the Tornle Sap. The lake becomesconsiderably larger for several months each year because of the backing-up of flood waters from the Mekong River.

b. Climate

Most of Southeast Asia has a humid tropical climate, which isconducive to the development of a large and varied insect population.Temperatures are high throughout the year; there is no season of pro-nounced cold and consequently no need for insects to have a period of dor-mancy. Southeast Asia is dominated by monsoonal (or seasonally reversing)wind systems that cause most of the area to receive its maximum precipi-tation during summer. On the other hand, the winters are comparativelydry over much of the region. (However, local variations in position withrespect to water bodies cause some places to experience their maximumrainfall in winter; for example, the central coast of Vietnam and. theeastern coast of the Malay Peninsula.) Because of the monsoonal controlof precipitation, seasons in Southeast Asia are customarily divided itothe dry monsoon (winter for most of the region) and the wet monsoon (sumerfor most of the region).

In general, insect life is much more prolific during the wet monsoonthan during the dry monsoon. The seasonal patterns of precipitation andthe surface wiads which govern these patterns are shown in Figures 3a and3b.

During the dry monsoon, which usually prevails from mid-October tomid-March, -ir temperatures are compara:ively cool and have fairly largediurnal variations (the difference between the high and low temperaturesfor a 24-hour period). Temperatures average several degrees lower in thenorth than in the south, but do not drop to the freezing level at anyplace other than the higher elevations. A typical lowland-interior stationmay have temperatures as low as 50-60°F during a January night, but thethermometer will likely rise to the 70's during the day. Except incertain exposed locations, precipitation is normally very light at thistime of year.

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Where the land is exposed to moist southwest winds, the wet monsoonbegins about the middle of May and persists until mid-September. Temper-atures reach thisL yearly maximum just prior to the arrival of the rainyseason, and, combined with increasing humidity, make the weather at thistime of year exceedingly uncomfortable. With the increasing cloudinessaccompanying the onset of the rainy season, air temperatures drop some-vhat, but sensible temperatures and human discomfort remain high becauseof the very high hutidity. Air temperature3 are generally in the high80's or low 90's (F ) during the day, and night-time temperatures droponly to the middle or upper 701s. These conditions are nearly perfect forthe propagation of a wide variety of insects.

Sumer rainfall is typically convectional (i.e., thunderstorms orheavy showers caused by heating of moist air), occurring most frequentlyin the mid-afternoon. However, convectional rainfall may also be triggeredby factors other than daytime heating, so storm activity may occur at anytime of night or day. Because of the prevalence of air movement from thesouthwest, the southern and western (wiLdward) exposures have dense cloudcover and frequent heavy rains in summer. It is not unusual for a wind-ward slope to receive well over 100 inches of rain during a single suerseason. By contrast, the northern and eastern (leeward) slopes are muchdrier, often with no more than 20 inches of rain during the same period.The windward-leeward differences are particularly noticeable along theArakan Yom^, the Annamese Highland, and the mountainous Malay Peninsula(see Figure 2).

Temperatures during the summer monsoon are not extreme, afternoonhighs reaching the high 80's or low 90's and nighttime minimums droppingto the middle to upper 70's. This is due to the very humid condition ofthe air along with the attendant heavy cloud cover. Consequently, thehighest tempezatures are recorded during the mid-spring period precedingthe beginning of the rainy season. Temperatures are highest at the lowerelevations and become progressively cooler with increased elevation. Thetemperature may be expected to drop slightly more than 3 Fahrenheit degreesfor every 1000 feet rise in elevation.

c. Vegetation

Southeast Asia, an important home of man for more than 3000 years,can nowhere be des~.ribed as having a "natural" vegetation cover. Forthroughout this long period of occupation, man has been clearing forests,burning grasslands, and replacing the natural growth with that of his ownchoosing, co that today no aspect of the landscape can be described ascompletely unaltered by man. Almost every so-called "natural" vegetativeassociation is secondary growth with probably no more than 50 percent ofthe original species still present. In some places the effect of man has

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Iibeen to increase the cover of tall grasses, particularly where there arefairly pronounced periods of drought. Elsewhere bamboo jungles may becomethe dominant surface cover.

Under the influence of the monsoonal climate, the character of thevegetation varied according to the length of the dry season and the totalannual rainfall. In sections where there is no long dry season and annual Irainfall averages over 80 inches, broadleaf evergreen forest is dominant.Where the annual rainfall drops below 80 inches and there is a well-defineddry season, monsoon forest replaces the evergreen forest. Where rainfallis less than 40 inches, the monsoon forest gives way to scrub f1:Ct.

The dominant natural vegetation types of Southeast Asia, therefore,are broadleaf evergreen forest and monsoon forest. However, there areseveral other types which may or may not fit within these broad categories,

but which are important for the purposes of this study. Therefore, thegrouping used here is as follows: (I) mangrove forests; (2) sandy-shorevegetation; (3) broadleaf evergreen forests; (4) moist mountain forests;(5) monsoon forests; (6) savannas; (7) thorn forests; (8) fresh-water swampforests and marshes; and (9) man-made or man-dominated associations. Thedistribution of these vegetational types, with the exception of sandy-shore vegetation and fresh-water swamp forests which are of relativelysmall extent, is illustrated in Figure 4.

(1) Mangrove forest. The mangrove forests, a specialized adapta-tion of the broadleaf evergreen, consist of a number of species whichgrow only along coasts where active sedimentation is taking place. Mostof these species have pneumatophores or "breathing roots" which projectabove the ground level in loops or "knees". All have structural adapta-tions which permit them to root effectively in unstable mud, and the exten-sive root systems, often beginning well above the ground like flyingbuttresses, may provide support for large trees. The chief differencebetween species lies in the amount of tidal inundation they can tolerate;consequently, there is a well-defined zonation of species parallel to theshore line. The seaward plants, being most tolerant of salt water, makeup the advance guard pushing seaward. At the inland fringe, the leastsalt-tolerant trees mark the transition to fresh water swamp forest orsome other non-marire type of vegetation.

(2) Sandy shore vegetation. Along the sandy shores of SoutheastAsia is a type of vegetation termed the Pes-carae formation. This corres-ponds generally to the strand vegetation of Europe and North America, andconsists of salt-tolerant short herbs, grasses and shrubs. It may form acomplete ground cover, but more frequently it consists of an open communityof plants.

8

IAlong the moister tropical beach margins, the herbaceous -egetation

abruptly gives way to beach woodland, which may form either a deuse beltof fairly large trees or scattered clumps of trees separated by open space.The trees usually begin no more than 75 to 100 yards inland from the shofeand are distinct from those found in other forests. Some trees of thisforest reach heights of 90 feet or more, nearly as high as the averagetree in the tropical rainforest. Undergrowth is dense, and combined withan abundance of lianas and epiphytes, it mekes penetration difficult.

(3) Broadleaf evergreen forest, The broadleaf evergreen forest.•of Southeast Asia is located on the poleward margins of the tropical rfin-

forest, and differs from it by having a greater proportion of deciduousS• trees. Typically, thiere are three stories of trees in addition to the

shrub and herb layers. Trees 150 to 200 feet tall are scattered through-out the forest, their isolated crowns rising above the second level ofmore solid green. These taller trees shed their leaves annually butappear to be evergreen because many of the species grow new leaves beforethe old ones have dropped off. Trees of this story have thin, straighttrunks despite their great height, and they are inclined toward flattenedcrowns. Many of the tall trees have widely spreading plank buttressessupplementing the root anchorage.

The middle story, reaching a uniform level at about 60 feet, consistsalmost entirely of evergret~ns. The trees are smaller in every respectexcept for the leaves, which are larger than those of the upper level.Palms and bamboos form part of the undergrowth. The herbaceous Lfyer issparse, consisting chiefly of ferns and dicotyledonous herbs, but nevergrasses. Conspicuous also are climbing plants, often with lengths greaterthan 300 feet, They consist of lianas which climb from the ground to thesunlit crowns, usin.; the trees as supports only, and epiphytes, whichinclude orchids, ferns, and wild figs.

The broadleaf evergreen forest is found chiefly in areas of heavy rain-fall along the southern coastal margins, particularly in lower Burma andin the southern Annamese Highland, where the heaviest rainfall totals arerecorded. Figure 5, a profile of vegetation from the zone of tropicalrainforest through the zone of scrub forest, illustrates the relativeposition of the broadleaf evergreen forest.

(4) Moist mountain forest. Above 2500 feet throughout most ofSoutheast Asia, the broadleaf evergreen forest gradually gives way totemperate-zone trees such as oak and chestnut. The canopy is more openthan in the broadleaf evergreen forest. Ground herbs and ferns are moreabundant, herbaceous plants often forming a thick ground carpet. Climbingplants are still abundant, particularly epiphytes, which appear to increasewith elevation.

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At still high-r elevations plants become progressively smaller, andthe woody species are often twisted and gnarled. Above 5000 feet theremay be a moss forest which differs considerably from either of the othermoist types. Here the number of tree stories is reduced to one, the average"height ranging between 20 ,ind 30 feet. The thick cover of epiphytes(chiefly mosses and livervvorts) gives a grotesque appearance to the dwarfedtrees and to the forest in general. Mosses hang in thick blankets every-where, often burying small troes and shrubs. Moss forests will not growwhere there is a pronounced dry season. In typical monsoon areas, pineforests intermixed with bome broadleaf trees occupy the zone above 5000feet.

(5) Monsoon forest. Mionsoon forest is the most widely distributedof the natural vegetation types in Southeast Asia. It is transitionalbetween the wet rainforest and the dry subtropical savannas. There arefewer species than in the rainforest, teak being the most widespread al-though it seldom constitutes more than 10 percent of the total forest stand.Where rainfall is relatively high, tCe trees are dormant for only a briefperiod, often putting forth new growth only 3 or 4 months after the timeof leaf Irall. The shrub layer is poorly oeveloped, but bamboo is abundant.Grass cover on the ground is unusual, and there are few ferns. Climbingplants are conspicuous, but they do not alter the open appearance of the"forest.

Under less humid conditions (which are characteristic of a large part* of the area), teak forest dominates. Teak is adapt'd to a more prolonged

period of drought, and usually occurs where the rainfall ranges from 40 to60 inches. It often is found in pure stands as a result of forest burning,

* because its saplings can survive fire without destruction and its thick,hard-cased seeds are also very fire resistant. It is a large tree growingto heights of 120 feet, and pure stands constitute an important resourcebecause teak finds a ready market as a cabinet wood.

Bamboo, a giant perennial grass, is another characteristic plant ofthe monsoon forest, particularly the drier portion of it. Large trees arecompletely covered with bamboo, for, as in the case of teak, bamboo seedsare fire-resistant.

In the still drier margins of the monsoon forest, a type of forestreferred to as indianz in Burma and vadeng in Thailand occurs. This forestdevelops in areas where the average annual rainfall is about 40 to 45 inches.Trees are small,. ranging between 30 and 80 feet in height. The undergrowth

t consists largely of .a tangle of grasses with occasional cycads. Bamboooften is scarce or missing. The surface flora is scanty, and bare soil iscotwon. Epiphytes are usually abundant.

(6) Savanna. In Soutbeast Asia open grasslands are generallysecondary growths arising after the destructio of the monsoon forest by

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S11

I :

burning or shifting cultivation. As is true in many savanna areas, it isa com-on practice to set fire to the coarse dry grass at the end of thedry season to promote the growth of the young tender shoots that are pre-ferred for grazing. Typically, savannas have scattered, widely spacedtrees which lose their leaves during the dry season.

(7) Thorn forest. On the drier margins oi the savanna forest thetree growth it mostly thorny. Acacias are the most coon, occurring asboth trees and bushes. They seldom grow more than 30 feet tall. As inthe savannas, grass is the domiuantundergrowth and tree climbers are abun-dant.

Thorn forests occur where the rainfall is less than 40 inches per year,with local variations caused about as much by soil differences as by rain-fall. The depth and porosity of the soil substantially modify the effectsof rainfall. The farther away from the humid rainforest, the more markedis the effect of soil differences on vegetation. The broadleaf evergreenforest and the moister sections of the monsoon forest are essentiallyunaffectred by the character of the soil.

(8) Fresh water swp forest and marsh. In many places whereland and water meet, the land constantly encroaches on the water. Amongthe more important agents in this encroachment is vegetation, which impedesthe movement of water and thus increases deposition of material carriedin suspension.

The primary vegetative succession in fresh water lakes and swampsbegins with floating aquatic plants associated with water lilies. Thesemay give way to a swamp sedge and fern commanity made up oi various ferns,sedges, grasses, and other herbaceous plants. These ore satcceeded bytaller plants including reeds, rushes, and ferns. The next stage consistsof shrubs and palms, which may be followed by a tall, fresh-water swampforest.

Marshes are widespread in the deltas and flood plain margins of thelarger streams. Seasonally inundated marsh land forms a belt many mileswide around the Tonle Sap in Cambodia.

(9) Man-made or man-domi0ated gat.erns While man has profoundlyaltered the natural pattern of vegetation in Southeast Asia, the centersof dense human population short tbc greatest impact. In addition to theirusual domesticated plants, densely populated areas have numerous non-cul-tivated varieties which show, by means of their patterns of distributionand the use made of them, the pervasive influence of man. Var!us typesof trees serve as sources of lumber, firewood, and fruits and uuts.Certain species may be nurtured as ornamentals or shade trees; wild grassesserve as forage for domesticated animals; and nuerous wild floweringplants are gathered and used for decoration.

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IThe most important field crop and the one with the greatest effect on

the landscape wherever it is found is wet rice. This crop dominates allriver deltas as well as most of the flood plains adjacent to the largerstreams. Wet rice demands a uniform but very gently inclined surface, per-imitting controlled flooding during the period of growth (the 5-month periodcoinciding with the wet monsoon).

In many deltas farmers have the problem of not only providing adequatewater for their rice plants, but also of protecting their fields frmflooding during the pzriods of heavy rain. Natural and man-made leveeshold back streams whi,;h e~ven at normal levels are flowing well above theagricultural land on either side.

In most of the low-lying delta lands two crops of rice may be plantedin a single year, and in the better drained portions dry crops (corn, sweetpotatoes, etc.) are frequently planted after the rice crop is harvested.Every agricultural household produces a variety of garden vegetables, andsurrounding every homebtead and paralleling every village street are fruittrees, palms, ornamence! sbrubs, and shade trees.

Under less humid conditions, wet rice fields occupy cnly a small pa.tof the total land area, mixed farming being more characteristic. Fieldcrops include peanuts, sesame, beans, cotton, millet, and an unirrigatedvariety of rice called dry rice.

Thi hills and mountains are sparsely populated, and in many areasI - "shifting" agriculture still goes on. Domestic tree crops are important,

including tung trees, Lea shrubs, and, in certain parts of the south,rubber and coconut plantations.

d. Ground Conditions.

While it is difficult to generalize relative to ground conditionsover so large and varied an area as Southeast Asia, it is important to

j recognize the influence they have over the distribution of the variousforms ol insect life. Surface moisture is essential to the breeding ofmany insects, and moisture conditions often determine what species willbe found in a given locality. This is particularly true of mosquitoes,but it is also true of most of the other insects. Moisture, either in theform of transient surface water or ground water, is usually necessary fortheir existence. Ground cover is also important to most insects, eitherdirectly or indirectly, providing food and harborage for their vertebratehosts (rats, mice, shrews, olrds, etc.), or refuge for the insects them-selves. The composition of surface materials affects distributionsindirectly through its adaptability to the needz of burrowing animals,both vertebrate and invertebrate. Some of the relationships between envi-ronmental factors and ground cover are illustrated in Figure 6, a cross-section of a stream valley in the Korat Plateau.

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Several factors influence ground conditions in Southeast Asia. Alllowland areas are generally flooded during the wet monsoon. Major streamspassing through broad flood plains develop natural levees which maintainstream channels at higher levels than the adjacent land. Thus after

- -flooding has occurred it is impossible to drain the excess water from thislow-lying land into the main streams. Consequently, the levees are generallyparalleled by fresh-water swamps and marshes (similar to the bayous of theLower Mississippi Valley) away from the main streams. This is true notonly of the major lowlands, but, because of the tremendous seasonal floodcrests, it is also true of the streams crossing the Korat Plateau. Mostof the land adjacent to these streams dries out rather quickly after thebeginning of the dry season, but the lower-lying oeltas generally remainsoggy most of the year.

Tidal marshes and mangrove forests are co-on along the coast, parti-cularly where delta formation is in progress. These are affected by bothflood water inundation and by the penetration of tidewaters, which duringthe flood crests greatly expand the area covered by water. Extensive low-lands are water-logged for pai of the year because of the intensive culti-vation of rice. Beneath the 'o:est, the ground is generally coveredwith a thin, spongy leaf litter. ±his organic layer becomes progressivelythicker from the rainforest into the savanna.

3. Harmful Arthropods

a. General

There are numerous species of harmful insects and other arthropodsin Southeast Asia, many of which adversely affect man in an indirect way,destroying his field crops, infesting his fruit trees, contaminating hisstored food, feeding on his clothing and other household fabrics, attackinghis livestock and domestic pets, and even eating away the fotndations ofhis buildings, However, the primary concern of this study is the distri-bution of insects which can cause direct bodily harm to military personnelin the area, and the enviro mental conditions under which these insectsexist. In varticular, emphasis is directed toward those species respon-sible for the spread of disease and infection. Tables I, II, III, and IVprovide a listing of the various harmful artrropods of the regions,including more detailed information for each species than is given in thetext. (See Appendix).

S. Mosquitoes

By far the most annoyirg insect throughou.: the region and the mosteffective disease carrier is the mosquito. individual species are foundin almost every environment, from the coastal margins to elevations above8000 feet. The one essential element for all is the presence of water,

15

regardless of its physicul qualities. Some mosquitoes breed only in clean,flowing water, and others in stagnant waters fouled by decaying vegetablematter; some are adapted to the brackish water of the coastal margins, andothers seem to thrive only in the cool, fresh waters of upland streams.Poorly drained areas such as the flood plains of the larger rivers, andinterior and coastal marshes, are particularly favored. Fish ponds, ricepaddies, shallow wells, borrow pits, and other man-made reservoirs oftenprove attractive sites for breeding. Permanent lakes and even free-flowingstreams seem to be favored by some species. Open water, free of vegetation,is least favored.

Though generalizatiems concerning envirovaent&l controls are difficultwhen dealing with a group as large as the mosquito family, there are anumber which appear valid. Water temperatures are important. Above 80°Fthe number of species decreases, and water temperatures in excess of 95°Fusually are fatal to larvae. Many mosquitoes escape excessive heat byoccupying moving water, such as that found along the margins of flowingstreams. Few are active when air temperatures are warm to hot and relativehumidities are low. Most remain relatively close to breeding sites through-out their existence, with major movements generally limited to less thanone mile.

In terms of human health, the more important genera are Anopheles,Aedes, Mansonia. ad Culex. Anopheles, the largest genus, is also ofgreatest significance in the spread of disease. It is chiefly noted as avector (carrier) of malaria, though certain species are also involved inthe spread of filaric•is. While generally described as lowland mosquitoes,Anopheles are found at all elevations up to 8000 feet, and are actuallymore effective in the transmission cf malaria at the higher elevationsbecause of the greeter tendency for the upland species to feed on man ratherthan other animalb,. Aedes are carriers of yellow fever in other parts ofthe world; although this disease is unknown in Southeast Asia, if areservoir host were to be found it could be introduced. In Southeast Asiathe principal role played by edes is as a transmitter of dengue feverand, more rarely, of Japanes. B encephalitis. It is also a possiblecarrier of the principal Southeast Asian forms of filariasis, Wuchereriabancrofti and Wuchereria melai. Mansonia mosquitoes are the more impor-tant carriers of filariasis, particularly Wuchereria malayi. Culex arethe principal infectors of Japanese B encephalitis.

c. Non-bitinx Flies

As a pest and disease vector, the non-biting fly probably is out-ranked only by the mosquito. A number of these flies, notably Chrysomyiabezziana, are involved in myiasis infections. 10yiasis may be caused byflies laying their eggs or depositing their larvae in or near diseaaedtissue of man or animals. In some cases larvae are found only or the

16

diseased tissue; however, more serious myiasis results from larvae thatinvade the deeper tissues. Any open wound or even bruised tissue mayattract flies seeking to deposit eggs. The more vulnerable areas includethe eyes, nose, ears, and the anal and genital areas. Intestinal myiasismay develop upon eating meat in which eggs or larvae have been deposited.Musca sorbens, a close relative of the cogmnon house fly, may be an impor-tant agent in infections of yaws, and others may serve as mechanicalcarriers of bacterial dysentery. Non-biting flies are found in almostevery type of envxronment, being directly related to man or his domesticanimals.

d. Fleas

Fleas are important as pests and disease carriers. All are para-sitic on vertebrate hosts, especially on rats and mice. These roden.sand their flea parasites tend to follow the major communications lines,and are particularly numerous in warehouses and storage areas. Especiallyattractive are grain stores, abandoned feed dumps, and garbage disposalareas. In residential districts in cities and towns, they are morenumerous whenever there is unusual crowding. Fleas are most directly asso-ciated with the spread of plague: Xenopsylla cheopis is considered to bethe principal vector of bubonic plague, and Nosopsallus fasciatus, acarrier of murine typhus, is probably the most important agent causingplague infestation among wild animals.

e. Sandflies

Sandf]ies are pests throughout Southeast Asia. They are capableof inflicting painful bites, and are involved in the transmission of kalaazar. Only one, Phlebotomus argentipes, is considered a highly infectiouscarrier in this area. Sandflies appear to be capable of breeding almostanywhere they can find unprotected soil rich in organic matter, usuallywithin short distances of houses and barns. Reservoir hosts are mostlydogs and rodents. Sandflies are sensitive to strong winds, bright sun,and even full daylight.

f. Lice

Lice do not constitute a serious threat to man in most parts ofSoutheast Asia, because they tend to thrive only where cool conditionsprevail and where an abundance of clothing is worn. Nevertheless, head,pubic, and body lice do occur in Southeast Asia. Occasionally, body lice(Pedtulus humanus corporis) may be involved in. the transmission of disease.Lice thrive under conditions of poverty, overcrowding, and the associatedlack of cleanliness. They are responsible for the spread of epidemictyphus, the most serious form of disease, of which man is the only reservoirhost.

17

g. Mites

Mites, like the disease-carrying fleas, are oriented chiefly towardmajor infestations of rats and mice, even though other animals, such astree shrews, squirrels, birds, and man serve as alternate hosts. Mitesare responsible for the spread of scrub typhus (Tsutsugamushi disease),murine typhus, and other rickettsial fevers. The incidence of mite-bornediseases is directly depender.t upon the affinity of the natural hosts toman. As man provides harborage for rodents the incidence increases.

A high incidence of mites is found both in the tall savanna grasslandsand in dense forests. Trombicula deliensis, probably the most importantagent involved in the transmission of scrub typhus, is more common in forestswhile the other important carrier, Trombicula aKamushi, is more often foundin scrub forest or grassland. The preferred hosts for both are wild (field)rats, which account for their primarily rural occurrence. The heaviestconcentrations are found in and near abandoned fooJ dumps, gardens, andneglected plantations. The more serious outbreaks of typhus generally arerelated to drought, floods, crop failures with associated famine, poorsanitation, and the destruction wrought by military operations. Mitesare sensitive to changes in humidity, and in most cases the incidence oftyphus is lower in the dry season.

h. Ticks

Ticks, like lice, may be involved in the transmission of typhusand other rickettsial fevers. There are two species of ticks common tothis area which may act as disease transmitters. Rhipicephalus sanguineus,the common brown dog tick, is chiefly found in or near human settlementsbecause of the close association between dog and man. It is responsiblefor tick-borne typhus, Indian tick typhus, and other rickettsial fevers.Haemaphysalis spinigera is more commonly found in dense erergreen forestswith thick undergrowth and an annual rainfall of more than 80 inches; it

is responsible for the transmission of Kyasanur forest disease. Bothspecies deposit their eggs on the ground, and both the larvae and theadult ticks attach themselves to whatever host is available, be it monkey,rat, dog, man, or other animal. Men resting directly on the ground arelikely to pick up both ticks and their larvae, thus becoming accidentalhosts.

i. Other Arthropods

There are a number of insects and other arthropods whose bites andstings are responsible for skin inflammations. These include numerousflies, midges, spiders, centipedes, bedbugs, and many others. While suchbites and stings are seldom disabling by themselves, they may easily leadto serious skin infections. Common to the Tonkin Easin and northern Laos

18

are Paederus beetles, whose body fluids when crushed against the skin may

cause painful blisters.

4. Cultural Environments and Associated Harmful Arth.opods

Throughout Southeast Asia, regardless of the physical surroundings,there are large numbers of harmful insects whose distribution tends to beclosely related to human population concentrations. These include disease-carrying flies; head, pubic, and body lice; bedbugs; rat-infesting fleasand mites; and an abundance of domestic mosquitoes.

* - a. Cities and Large Towns

Urban centers, though generally less bothered by harmful insectsthan rural settings, are, nevertheless, infested by a number of disease-carrying arthropods. Probably the most dangerous of these are the speciesparasitic on rats and mice. These inclu#4e fleas which are responsible foroutbreaks of plague. and mites associated with epicemics cf typhus. Heaviestinfestations of rodents and their parasitic guests are found in and aroundport facilities, railroad depots, warehouses and storage centers, anddensely crowded residential districts. Non-biting flieb are everywhere,particularly around stables, open food markets, and occupied houses, andthey are especially abundant during the rainy season. The so-calleddomestic mosquitoes are numerous wherever there are uncontrolled breedingsites. Perhaps the most important of these is the dengue fever carrier,Aedes _aeIpti. However, species capable of transmitting malaria, filariasis,and Japanese B encephalitis are also found. Although mosquitoes common tothe larger cities are generally among the less infectious carriers ofmalaria, serious outbreaks do occur from time to time. Body lice, respon-sible for occasional outbreaks of typhus, may find favorable conditionsin the crowded slums of urban centers, particularly during the cooler partof the year.

b. Villages and Isolated Rural Settlements

Harmful insects found in villages and rural settlements aregenerally those of the surrounding country. However, the mere presenceof man may alter drastically the distributions that might be expected inthe completely natural state. Mosquitoes are parti :uiarly abundant aroundthe smaller human clusters and include both the p-4narily domestic speciesas well as species which feed indiscriminantly on man or cattle. Cattlesheds located between breeding grounds and human habitations may serve aseffective barriers; for this method to be effective, houses should belocated at least 200 yards from the cattle sheds. Non-biting flies aregreater pests in the more rural setting than in towns and cities, due tothe fact that many are attracted to cattle and other livestock as well asto man. This is true of many of the natural vectors of myiasis, yaws,and bacterial dysentery. Sandflies are numerous in village and rural

L .19

* homesteads, because their favorite breeding grounds are on bare groundcontaminated with decaying organic matter such as is found in the vicinityof houses and cattle sheds. One species, observed in the former Frenchterritory of Indochina and likely found in other areas, is a vectox fo.kala azar.

Human settlements, whether rural or urban, generally attract numerousrats and mice, and the parasitic insects associated with them. Of parti-cular significance in rural settlements are the Trombiculid mites respon-sible for the spread of scrub typhus. This is because their rodent hostsare principally wild rats, which are seldom found in or around cities butcommonly infest rural areas where man has been. An unusually high inci-dence is associated with tall savanna grass, and recent findings indicatethat heavily forested areas are also amply endowed with this pest. Mitesare far mnre numerous in the surface litter than on growing vegetation, andmen sprawling on the ground during rest are likely to have their clothinginfested. While the incidence of plague is generally lower in rural thanin urban environments, plague-carrying fleas such as Xenopsvlla cheooisare common. Ticks are numerous in all parts of Southeast Asia, but theyare most abundant in rural areas., Lice are common everywhere.

c. Ricefields

Extensive portions of Southeast Asia are used for cultivation ofrice. Although a variety of arthropods, including r-_ats, midges, all kindsof flies...e, s mites., and ticks are common, mosquitoes are the mostsericus tbreat to the health of man. Among the myriads of mosquito speciesthere are several which are disease vectors, and a number of these areconfined, for the most part, to the ricefielde. These include &2onhelessinensis, a malaria carrier of some importance in both Burma and Viein-mand a possible vector of filariasis, and a number of Culex species capableof transmitting Japanese B encephalitis. Also abundant in the ricefieldsof Southeast Asia are Paederus beetles, whose body fluids may cause blistersif the insect is crushed on the skin. These become a problem during themonths of May and September when they are most likely to enter houses.

5. Natural Environments and Associated Harmful Arthrovods

a. Brackish Coastal Margins

Although the numb-r of individual- of a single species tends to belarge, the number of species adapted to the brackish coastal margins islimited. Mosquitoes are probably more numerous than any other insect group,and the individual species adapted to this environment include important

malaria carriers such as Anopheles sundaicus and Anopheles umbrosus, themost important dengue fever carrier, Aedes ae.Zvti, and, less frequently,filariasis carriers of the genus Mansonia. Gnats and midges are numerous,

20

and those insects parasitic on man, s-ach as fleas and lice, may become

problems if preventive measures are not taken by individual personnel.

b. Delta Plains, Coastal Plains, and Flood Plains

Practically all genera of harmful arthropods are found somewherewithin these low-lying areas. Mosquitoes are abundant everywhere, but theincidence of malaria is lower than at higher elevations. This is becausethe more abundant Anopheles malaria carrier in the lowlands !end to bezoophilic (i.e., preferring animals) in their blood feeding. Mosquitoescapable of transmitting both filariasis and Japanese B encephalitis arefound in most low areas. Mansonia species, considered to be chieflyresponsible for the Wuchereria malayi variety of filariasis, are more wide-spread in swamp forests aid marshes. Flies and fly-borne diseases suchas myiazis, n-aes, and bacterial d)sentery are ubiquitous in areas occupiedby man. Trombicclid mites, responsible fir scrub typhus, are more numerousin rural lcwlands than anywhere else in Scjtheast Asia. They often reachepidemic stages during mi1"Itar7 operations. The spread cf typhus infec-tions tands to follow drainage lines. Rat fleas, which are carriers ofplague, are also most n'2merous in lowlands, especially in or near cities.Non-biting flies, biting flies. ticks, lice, and other pests are found inmost lcwlands. The land leech, a blood-sucking worm of widespread occur-rence, particularly prevalent in the rainforest, is a pest perhaps morefeared than any of the insects. in marshes or swamps, the water leech mayconstitute a similar problem. Though not extraordinarily painful, thebite of the leech bleeds profusely, and secondary infections associatedwith it may be disabling.

Subhumid lca!Iities, as in central Burma, have a less varied insectfauna than humid areas. The genera ts:z to show adaptations to the morearid conditions: nos: are noctirnal, and many have heavy waxy externalcoatings which help to prevent loss cf body fluids. Mosquitoes are farless numerous In arid places be:ause of their tendency toward excessiveloss of body moisture thrcugh respiration; and those found in such environ-ments art most active during the early morning hours when temperatures arelow. Incidence of disease zaused by Trombiculid mites is reduced underarid conditions and is markedly lower during :hc dry season. Biting andnon-biting flits are fairly n,=merous, ta are _ spiders, and scoyrions.

Tall sava:na grasslands have the greatest abundanze and variety ofinsects auring the wet season. Rodents serving as hcsts for disease-:arry-ing insecý& find good harborage in su:ch areas. Trcmbiculs deliensis, thechief vector foz s'rub cyphus. is rarti:c-larl- abundant here. Mosquitoesare most numerous in the savanna during the rainy season.

c. Elevated Plains, Low Plateaus. and Foothills

The chief distinction between the barmful insects found here andthose of the lowlands is largely in lerms of m os. The more zommon

21

species found in these areas of intermediate elevation include some of themore virulent malaria carriers in Southeast Asia, msch as Anopheles minimusand A. leyporiensis candidiensis. Both are abundant in foothills, and bothfavor the cool water of slow-moving permanent streams.

d. Hills. Mountains, and Dissected Plateaus.

The variety of harmful insects in the upland areas and their patternsof distribution are limited largely by exposure and elevation. In general,both the number of species and the total number of individuals tend todecrease with increased elevation and from the more humid windward exposurestoward the drier leeward sides. Mosquitoes, though less numerous than else-where, are found as high as 8000 feet, and include species known to be vec-tors of malaria, filariasis, and dengue fever. Host mountain mosquitoes areadapted to the fresh, moving water of permanent upland streams. Typhun-carrying Trombiculid mites have been observed at elevations up to 8,000 feet,with infections reported up to 7,000 feet. They are particularly abundantin the northern uplands of Burma. Plague-carrying rat fleas are also foundin the uplands, usually in conjunction with the presence of man. Rosopsyllusfasciatus, a possible vector of murine typhus, is particularly well adaptedto the relatively cool conditions of the uplande.

Figures 7-11 show association of terrain and vegetation patterns withharmful insects.

2.

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41... 4,. v.0....,. cod 0b...h .c . ,h c 0 . ,&08 .. . .,..E. b..; ,.

S 4.00.00ect o dt .00f 4o ees and .ccco Ii.,* 45i4o cclsdc~lt scrco b lypc.s ee i *V c dkc•..4.44.0. iplc;,. cloogI * Ok 4,0,I 000.04 H..... Vellcc0.og sod '0 44.00 qplogol• cod O•ch. {loch yp0o~00 kcoscINoJd p.ss billies '.Ot b. c poobli' coo Go,,. 4.ckolcch0,c , l • o~d 005.0 ,0 4.ick| tlM.~i ....... t. i~s •, 00001,0 A ocI.led p..sl 04. *,k.r l*.( 4 . *peds o scid.; -.o•S .r •p~d.,el .."listed .000s .. d cc... 4..cc ci sos

4. 4.00.d ond 4.., ogl 44,., o1, Icood 0(o009.00s M@,~

i.oc .o 0cc4

.., Ocood. M~d d *s 00d i 0€tso (OcO 4....r c*d loloc,,

/ ~/-./ /

",/ I-. / / //

0 C/

ph- 1:0-0 / 4...0- 0c.'5

0 0 C of 0 0 .

11D I

12040'N

1030E 105 0 E

SS-SECTION THROUGH CAMBODIA AND SOUTH VIETNAM

ING VEGETATION AND ftARMFUL INSECTS

"SAVANNAS MONSOON FO USlS VIlAGE AN DO AU RA t MOIST MOUNTAIN fOII $T"Not~,q,... (.-..,o..o S(IIIIMSNYS Motcd,.e See *..* ha'

Tw.lh.c.i.4 al.,e (n.&'Ide 8. ,eve 9 .... 4 ..o., O,.....,. 4 o *d .:d hgL*, '.,,,ov, .. oIo..o so.-f,.h,, IJ . $.Ito~ |l 'I 0.4d J~p.e...e . A~C.r~- q,,*,o$ .. 0.G4J.0 0ey o el *1 r~ l~'

0A4 .4.., *,O .. #..tn., de.5, ..... ,,.J d.t.~* '...t 9.1....... cod Jar- of 9.1..... 0i o *t.* '*~glee

. l otn••(u *e5 sec:o• I,,oh,.c~l, a..,. S e..aephol.hs.'• I-oe.ch,, d .4 e a,,.. •

Na l ,o• m iIk pl*, 9Rd(igI al., la o•b b,pI ,) ik ,h..d,,c..,.'tac@ ,.M o. fe

op.4- .- ; .5. I?~a.., sri typisa *.- _1. -"" I_,. ,-~ ,*~'0O O oI. o !.

.- ( .-i &. . -. , c--- . -d . --- o.0I~p.8I,.,.,

1;"" 0- -an o- d 1-

I.., nE 9....s.. h..-50 n.5_-.5 *,s . s- ... .. ',- ..-..r¾d

.- d

I N'

0 c 0 Cc 0o 0 or 0 a

a c w -0 a

00 0 'a 0 0

I I0ID I /

le -TN

050 E 108 0 E

Figure 9

31

DIA AND SOUTH VIETNAM

FUL INSECTS

VILLAGE AND RURAL MdOIST MOUNTAIN FORESTS 'MOIST VEIEGNEEN FOl$istSt 7AIMENTS M f.qeo..' fe.e. hoC *' Ab..do.t so'.;oes

qo.So., •*l~o,*a. 8.; *en** r,*, O *I etl e IjfotIsmdlcet |I... Jo p~on., S *n...pk-

4.* d l- 4 jon Jp- • laas od d..'.. f-ve, ohf,0 J:::-",."n •, •

's. B .oc.pl~ei*v ci ..n c.oob,.I8c o.h s ).,'e ..ttb 'y' (.o.oy~ ,os yeo..8 k, *L •

obo'.dooco CI @f Oft pI.,.) 0$.) O a | t (plao.)e '. |o-..o.s) ,,ch'st*(k I.vts

6~.ec. IhoI. ow. s..,. .,e .,',ojoos Iovofo.bI Ie, oltt 0.8• nj.. (iccb .,pbsI

coId t..os (,sc• typkvso.( IInd or 8• c~hc 'l t *ee hoI o..e iee t. o .le dto.

eClho *4k I.e.,,) c•oos.. I... (eo,8o--.c*. '- nost ,n.eCC$ So1i II..$

.. do.'c ooy IT. (nd aso

-. - "\oI101c \8ho

d d

CC C C

0 0

.11 0*- O ~ O* S ~ u

""-- U T HE 13 025'N

'I N2°0"

"N A- *.-. Ho

ewl

1080E

PHYSIOGRAPHIC CROSS-SECTION THROUGH SOI

NORTHERN SOUTH VIETNAM SHOWING VEGETATION

SAVANNAS fVILLAGE AND NUIRAL NPLA -D PLAINS FOOTHILiS AND FNLLS MOUNTAINS AND 1

11C| FIlD$SiasId*,, STLM~SLOW PtASTAU' DSCTEDPATEAS ANDOn~in ;$IDS.,.1aI

s ti ad id d aii, . * ositoes Melqal... I, 8 000 40e 11ton,(sIrub typ•lesn nba.. qn.IaaIc LaIpd. widnus- .1.,.atik il,,, vtIden.,. I . . . .Il4n

*n ) Na n.6.l eo-* j~,*; Ratti. I.Taias,,. *d M. dan . In.., o| Japan... o *n a.*. Io. . . ,,* an... S .pha hh. N. n k ,"layk.as ay. and ik,. **ea S *no* ha¾ " a topkeI h• Sel II.e. Ipiegtol and fYohi vs Iifeclon. .1 I.Ia,,a$s od dIo.. b.o. .l- Ia nd .....inl~i, *SII h ,Is,*• |,.,. aknhd%.ua *. .e* ... lw d, fl: .d it a l* em ¢.I.te.ly(h•ad •y ,denn..e ae .. e..- se

I.- n... p.,an i I ,aibaiag buinlid i..Isci~b typI,$) I. S CO0 (iab 0'..us. end Nok, (itch*lhe, Itch Ineai.) .. ,- and shin *nlociian.I snd N.kl8

I,,I il n~ .lEif~.t..I.. l. *, iodh,. ddtlcd c~~e |€••l! |• ¶eb. Ih~ nl~f i i*c ni and l~nk* (i,.b ty. ~liACl [p.~e,, *r* and 5k,, ,n.,g- end *nni. *i. at.i~e ...daIan ai~n l~t ht.aal ,.b~~I-ba ae*d *ihei i~ck fEvnoi; aI. a- "aentI *nd •,ca (lna@ .c i,lns(lyvJ pisus Oe c,4 It*e mt, |ecu

o sq ,,I o o a b n n d (n l an Gd ., teh ii~ rc h tph.. san b a d a n t I6 lii. li.t ly ~l I ei..i d Id a r,a*n .. n( al w .it~ • .ItI ti t a orei t e e.s k e, .In i j, y .a tc i edL4ek$yph.$ n.ad b.... I. I .m

.4- -. a 1dk.in I..d .,h., .l. 4-0asb.

C 0 00

\\ 0

o .- C t

160N

1050 E 1060E 107'E

Figure 10

33

OSS-SECTION THROUGH SOUTHERN LAOS AND

AM SHOWING VEGETATION AND HARMFUL INSECTS

IHIMLS AND INILS MOUNTAINS AND a' LU1 FlELC; CITIES AND LAROID LOWLAND PLAINS (C...1.1CIDISIH PLAC.EAUS M.~.. o ~..I. TOWNS Dlaadh~d

* s attO~s IMasqsVI s 1. 8,000 feel M •. a.aad Jp 0:...t, esqit. c. Aboad a nt osa n eas .1kln. ,,, I., . .o a S.n in fe.lInd., , lfevbe..d g........d aIoC-dA.t..i: :::,...,.~,.nt:al,- S:: *tOp I .. sp'l~ Non- btllng **es *ee,In,,, nd n o.e oalld d~enise fee .n.hI.fo.n Sat

(..galad lettna Inhonstan 1IIs.osadSa Iie ele.ef ,- .eadst h• ns See *nalo snoIts ed o- II.d Jopongea *a tnIphs (horah

(ln lhg a a alo cn .eN a cahi e.

, t+• d.

. b t t tnygot ype yc oa c attun n , n p a et

siJ slbeynvt ,nd ldeat Sa fe .er e plse .c na n-bIt a | . hnts) crooe f Ie (pague r,dgos sumrou nhaltansi nd typh s) cerume tata pottl s Alnd

1.4.t ('.o1 I,. IIh., (ayesass. aye *nd 51..tot a lc. cad finals or also otoaon fleas (fe.*ae) alenof t); d•R onS a b,h.,; lhes, Iry,e..

fanos) as. a. la,en). *nd It.c (np~d n...t typhus,) poses as ala IIhe auth. )e.ad smea.. hkasahnld pasts ey. a•nd shun ,nfectns) hula;•

nlm Iat.,ted !dnt•fO €* tonI tnae¢. canshttata nnt@t Ien,1

.e. s|on.ly saiotnd I. Mltn. Icru. typhus) to un I *et dges .nd rinals ITch se-.

t|es e f1Iound ptoblems .a *Il nsee, SDod. ItCh, .nsncts 4.5.catng beanllosaey st.I ,aniesed press and faitnttons en econston Iend

l(hck typhu~s and eaher tclt fontys) 6. a seasonal ptokle Pu. •. cooler ant ..J"s leeches, , densn Iota,, an~d

*nd btlsngf uhn. ei lt.ase a -Sn9~alpnia. nnln laeehtas ,n a s

I /

:1. c'.. n

.J- ~ ~ ba. the .1'. S h.. 6

V H 9

i~D ,o oa i160N

vo 107 0E 0 °

Figure 10

33

PHYSIOGRAPHIC CROSS -SECTION

SHOWING VEGI

UftAND Ft "'M S, IOOf..,LI1 ;_ V3&tADIS AND MUN4AL SIUM5NIMIS SAVANNIA. HUS MCU'4IANlOW PtAVIAIJ .. ,,_ f .. 1-q.. ~,, * PLAIIA.S.

.. n. 4..e-.I., o,.. h..*.f..,. .. :', _ 4 ... 4,,.. . ~.* - -.. , -I-4,. Ah

14.-4o41... t .a .) e. p4-9 o. nIp a. h b~ .. 1. - .7., yh. .... 4 .. w* .4.0,

0- U. 0*. ft- -

an .C * c an00~ 0 0.~ c ... C -~

0 VN x4 00

II

20047N

1010E 1020E

OSS -SECTION THROUGH NORTHERN LAOS AND NORTH VIETNAM

SHOWING VEGETATION AND HARMFUL INSECTS

• MOUNTAINS A ND O'$SICITI LOWLAND MI CIPftAS osit$ ANI LAIDI IC

. .. . - 4-" *L ? A l .. . . ... ... .. . .I 4 * . e h .5 . .. . . ..-.ot 4..k~v .9*{.0v aea!ir,~ •dRw e.. e. u.. ,;*,,lI ~. j .~lIt *...- 4.,.4 4n.......,.t I.,.t iek.. 45 *..t,.efl . P.~

. i.-,. AlM . ., .. " ... 14- 1.".# J .•.e* .J.f.II. I.,a. 44....... 4... .1 dek. . .

) I* 4'O .0or i*'e 09 ,v b y*. .4 0 4•d@0 let.9 bert} 4..'. ik*4,..(•~i N .. t •t.. f l.. I 4• 0.5 . 1.9 N.. t pLvt. *.4•;e I*0

. V* 4. (.4.44e ew- ft... . ....f .%..I, A.y.,.d,

e50.*, 9•* wak,- L ,•l. Ne k 'I 4l, 4,.e (h t 4p, .d.. e- * *e~t t I el, ,- e.e I.e.. *k, * 4..},~d't le 4.,. i ,b,pk .~ e,n!...9k.~.b-4 N.4.*t. b... . . . ft . 4.,,-d .. . .& . ... j*,j**I.

* V, , ,...h..hk.. ,,tA, i.e. 4. ... * H.. ".

•c I., c cee

5 00 0

-- , 0 O C.0

, 0wL-0I a

Tzj NilA'_ 'iA

Figure hla

(C5-KTrZ

|!0

N LAOS AND NORTH VIETNAM

JL INSECTS

(l~li$ A140 LAlCI IOWNS StAAKISH COASIAl MA46,ml

*~ 1.. (...- .... .......

i- .. 4D

00

Ce 0 '

21a 17

-- 2Oý47

107cE

PHYSIOGRAPHIC CROSS-SECTION

SHOWING VEGETATIC

*. •. -.- , ~- o.. -

Goo

Mgn L

* 4 , 11 /Ž,-,1 -. . . .

20o47 N L

10 -

I*..*.E 1.N.2-* • .

-SECTION THROUGH NORTHERN LAOS AND NORTH VIETNAM

EGETATION AND HARMFUL ARTHROPOD SPECIES

t*V&tA .A.S 0 t.. 44 (.*.*D

o c

I I i2 ;AOI--

Figure llb

37

*4 VtI$ADM*.n .q.s...,. .. t.s(~t N ,G ON

_.•l. t'.~,'* ..- JeN.4.a'

~ ~ ACb*~.4S

RN LAOS AND NORTH VIETNAM

RTHROPOD SPECIES

'A-" IC! -'s olsf4 ^, G 1*040*SI t'. COW..A U*4031-s

5.." ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ -r -"" s" - .,. *t *% f4. d.4M...

t.33.~~~~-k rr.',o.33 ~l3

.. 0..t~d**qCt.3 .. , J~It'...1fl4*.:. 4

*3 MAG ~.' I... ~ .4 k~~.A 3~4'f"T'C3 . . .

*3~53'.4 4~~~ .. e.'..4, ~ 5p,.,,'l, ..a.4 .*e r.5. Mn. 0Jn. 0 . 50

'CC *' *3~.*3 ef A.." ~.5.. I'C Sas~~s

L,** b~.% 3 -- ' 33 ,.

*4 ' r ',tt. (4

R 153 Ct.M - 5.3 3." .. .14's.5. .~ 23 4 3y7

S5- ~ *Sac .s..,. . . . . . . . . . . .

H.5A. . 4.

C' p~on

20A'

i07O

6. Selected Bibliography

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Barnes, M. E., "Notes on the Anopheline Mosquitoes of Siam," A.,-J •2L,Vol. 3, No. 2, pp. 122-216, 1923.

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Brain, Ralph A , "The genus Culex in Thailauo (Diptera: Culicidae)," Con-tributions of the Mosquito Fauna of Southeast Asia, Contributions ofthe American Entomological Institute, Vol. 2, No. 1, 1967.

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Causey, 0. R., "Some Anopheline and Cuiicine Mosquitoes of Siam with Remarkson Malaria Control in Bangkok," Am. J. H.E, Vol. 25, No. 2, pp. 400-420. 1957.

Cc'l~ess, D. H., "Notes on the Cultcine hosquitoes o' Singapore. II. TheCulex vishnui group (Diptera, Culicine), with Jescriptione of two newSpecies," Ann. trop, med. Parasit., Vol. 51, No. 1, pp. 87-101, 1957.

_ "Notes on the Culicine Mosquitoes of Singapore. III. Larvalbreeding places," Ann, troE, Med. Parasit., Vol. 51. pp. 102-116,

1957,

Co-e!!, G., "Notes on the Distribution, Breeding Places, Adult Habits, andRelation to Malaria of the Anopheline Mosquitoes of India and the FarEast," J. Mal, Ins:, India, Vol. 5, pp. 399-434, 1943-44.

Cruickshank, J. A., and R. E. Wright, "Filariasis in Cochin," Ind. J. Med.Res., Vol. 1, No. 4, pp. 741-785, 1914.

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39

I

Distribution of Mosa ~toes of Medicl mLjpý;tance in the Pacific Area,Navod N. 93, urea u:Redcin =dSurg.7,Nav Det., Washington

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Gilmtour, C. C. B., "Bubonic Plague, Rats and Fleas in Singapore," MalayNed. J.., Vol. 9, No. 4, pp. 177-181, 19314.

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40

Herms, W. B., Medical Entomologwy, Macmillan, New York, 1939.

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41

IIMichigan, University of, Department of Geography, Analysis of Geozxaphic

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42

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43

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", "Studies on Filariasis in Malaya: The Efficiency of Mansonite v.loTripalpis as an experimental vector of Wuchereria ,alav," Ann, Tro5,

Med, Parasit., Vol. 51, No. 4, pp. 422-439, 1957.

Wilcocks, C., "Medical Organization and Diseases of Burma before the JapaneseInvasion," Troy, Diseases Bull., Vol. 41, No. 8, 1944.

Wilcocks, C., "Medical Organization and Diseases of Thailand," Trop, Diseases

Bull. Vol. 41, No. 11, pp. 887-898, 1944.

Williams, L., Vegetation of Southeast Asia: Studies of Forest Types, 1963-65,U.S. Dept. of Agri., Research Service, Washington, 1965.

Wormersley, H., The Scrub-Typhus and Scrub-itch M~tes (Trombiculidae, Acarina)of the Asiatic-Pacific Region, Pecords of the South Aust. fuseum, Vol.

10, Nos. 1-2, 1952, 673 p.

44 I

APPENDIX

Table Pase

I: Harmful Insects of Southeast Asia - AnophelineMosquitoes 46

II- Harmful Insects of Southeast Asia - Mosquitoesother than Anopheline 52

III: Harmful Insects (Other than Mosquitoes) inSoutheast Asia 56

IV: Harmful Arthropods (Other that, Insects) inSoutheast Asia 60

Vi! . . .... . .. . . ... ... .. ......

LAffit4 I- HiAD2UL INS~ECTS 0F SO4JMMAST ASIA - 5PaILr.E )t)S U1T

Species Distribution Brezdlng Sitiaation Elevations Affinity to Han

Amtu G~J eneral Most frequently bree'4 In rice- More comm Adults foun( *n isotb .7Donitz fields and fresh water ponds. in plains houses and ;,-v sheds.

Also, i~z14jtt! cha mels. leading to Prefer catlci. botttanks. with grassy margins, hills, but feed on am in, thecreak pools, roadside drains, foud at absence of cattle.ane river bedv. Most often both highin ricefields lust before bar- and lowvest or when fallow, elevations.

A, annylaris General Prefer still watet with algal Most common Greatest frequency inVan der Wulp growth and floating vegeta- on plains, cattle sheds, but also

tion. Found in slow moving but may be fairly comocn inwater, but not preferred, found up to hou,-es. ConsideredLarvae found In tanks. swamps, 7,000 feet, basically zoophxilc,ricefields, and borrow pits. but will attack mnOn occasion in tree boles andcut bamoo.

A. balabazensis General Species of forest and forest Broad ele- Though generallys aisas fringe commonly found In clear vational classed as wild mos-

*(variant of A.water of deenly shaded jnn- range. quito, will enterj euiospbvrus) gle pools, but also fotnd to From near houses to feed. Most

breed in open sunlight in sea level nuterous in areas wherebomb craters, wheel ruts and to moyre men and cattle are.smiall ponds. Occasionally than 3,600found In rock holes of mnon- feet.tain streams.

A.barbirostrias General Prefer sb*.ded water wiith emer- Broad ele- Classed ats wild mos-Van der Vulp gent vegetation. Common in vation quito but will bite

marshy forest areas. May be range, anywhere at aight andfound in fresh and stagnant found in in shaded situatiznaswator, and rarely in brackdish both plains during the day. Preferswater. Commn settings in- and moun- animal blood to that ofcluz~z -rassy forest pools, tain streams. man. Though gecarallysprings and dam pools, irri- w~re in houses, ingation ditches, with vege- Malaya no preferencetation in ricefields, swaps, shown between housesborrow pits, and artificial and barns.containers.

4,cilicifacies General Prefer clean, fresh water, Generally Wist coomen in ruralGiles Foud in sluggish streams, in plains, sttting. Indifferent

irrigation channels, rice- but may be as to cattle or man infields (while plants small or found up to blhod feeding. Greatestfields in fallow),* ornainental 7,500 feet. human affinity wherewater, swimming pools, and cattle scarce. Restsshallow wells. occasionally In cowsaeds and houses.in brackish water. Bites man freely.

A- fluvist~lis Northern Prefers clean water with emer- Seldom be- Breads most comonly injassection from gent vegetation in open sun- low 1000 immediate vicinity of

Indian to S. light, such as foothill feet or human dwellings. SeemChina border. streams, springs, Irrigation above 5,000. to prefer human blood

ditches, lakes, and edges of to that of cattle.suaps. Less common in rice-fields. Moving water pre-ferred.

4.lapoiensis bteotd I;- Prefer moving waters of slug- From low- Most frequently found inJones Surma and gish streams or slow flow of lands to cattle sheds, but may also

Indochina rice irrigation. Along marshy elevations of enter human dwellings.edges of lakes and poads. 6,000 feet.

Diurntl Feeding Seasonal Flight Importa-ce as aPatti. n Rest Pattern Distribution Range Disease Carrier

$egin to feed in Rest outdoora, Found in abundance Capable of Malaria cLrrier of secon-early evening. especially alon$ after rains. No good flig•it, dary Importance in Ido-maxim%. about dsa stratm banks. pronounced season- 1,000 yards china. Likely a carrier inmidnight. ality in Southeast or more. other areas. Possibly in-

Aria, but heaviest volwve in transmission ofin Uovember and filariesis (Wuchereri ban-lovest in May and crofti.June.

Begin to feed in tesc along over- Found thrc-h-hout Capable of Malarier carrier of secon-early evening. hanging %trea year.. Greatest long flight. dary importance. PossibleLargely completed oanks and in tendency to enter Up to 1,000 carrier of filariasis Q•-by 11 p.m. cattle sheds. At- houses during an- yds. cbereria bancrofW).

tractied to arti- tmin. Peak in nt-fizial light and hers in May, lowof te rest near during coolerlight source. months.

Noct-urnl activity Comnly along .tmbe-ts fluctuate Flight range Malaria carrIer of majorwith heaviest steep strea during year. Peak up to 800 importance in all S.E. Asia.feeding late at banks by day. Sept. to Nov. yards. Generally most importantnight. Will feed Those which have carrier in areas treatedoutdoors as well fed in houses at with DDT.&a in biuses, night may rest in

houses during day.

P Principally at Rest by day in Continuous through- Relatively A malaria ca•rier but notednight but nay cool dark places, out year with fa- short flight as Important in So•theastfeed in shade such as shaded vorable breeding range. Asia only when occurring induring day. strean banks and sites. Large nun- Rarely more extremely large nzu=ers.

stone walls, bers in ricafieLds than 600 Possible carrier of filaria-during early part yards. sis (llchereiLa bancroftiof season, and also and X. aalavli.numerous as p2ddywater stagnates.

Fred largely kests in cow Greatest incidence Long flight Considered a carrier ofbetween 9 p.m. sheds and houses during wet mioroon, range, one- malaria of moderate importancecad 2 a~m. In dark corners, but continuous half to one in Thailand and Surms.

throughout year. mile.Lovest numbers In

tias of highesttemperatures inlate spring.

Most take blood Host rest outside No pronounced sea- Flight range Considered a malaria carrier

meal within 1 1/2 along steep, sonality noted, up to 800 of limited importance in thishours after du,.i, shaded banks yards. area. Responsible for occa-Enter houses ii during day. sional intense malaria infirst quarter ot areas where zound.night.

Nocturnal feeder. Rest by d-y in Abundant in Arakan Flight rangr Considered a malaria carierNf cattle sheds, or (Burma) in early up to 1.000 of minor importance in this

on shaded clay part of year. Host yards, area. Possible infector ofbanks of straws. coIon in hill sec- Vuchereria bancrofti.

tions from Waythroagh September.

TABLE 1: iPHMML INSECTS OF SOUT~iCAST ASI. - AmrOtLIKlE MOSQUITOES (ConL.'8)

s$ecies Distribution Breedin& Si:•xZ"on Elavations Affinity to Han

. jear- Noted in Prefers slow moving water. Foothi11 Mthrcpophti.c, bu"Lnis tandi- u Fuund alc.-g grassy margins of rivirs up will feed readily on

.•r In'Jochina. rtreams and rivers in irriga- to mod- cattle and other ani-Koldztmi and Thai- tion ditcnes. svwaps, rice- trate up- mals. Often found in

-nd. fields, and seepage outlets. land eleva- human habitations.Especially abundsnt tn foot- tions.

hill rivers.

A. o General Breed in --mall muddy Fools. Primarily Usually found in housesDo%!,-% buffalo wallows. wheel tracks, lowland at night, but more fre-

sewage dralna, rice fields, species. quently in cattle sheds.artificial containers, and See to prefer cattleswamps, to L.

A. lItifer Peninsular Preference for dark brown Lowland Hay attack man in thadedSandoshma Thailand water of peat-filled ponds, species. areas during the d4y; and

and allaycia Cool water preferred. Found will enter houses forin shaded pools. Will not blood weal at night.breed in stagnrnt agriculturaldrains and brackish coastalwaters whce fresh water situ-ations not available.

A. 3!-ulatus General Prefers water open to sky. A Generally >--on it. houses atTheobald sun-loving species. Abundant an upland night but not An day-

in water with mrts of grass speries. tiwe. Feeds with equalroots and green algae. Found Found at vigor on men or cattle.ia streams and r}ver beds with elevations Human affin!i'y in partpreference tor seepage rivers. from 3,000 depe4-dent cpoz tbh num-Found in cletazd hilly areas to 8,000 ber of cattle present.and not in h-ll jung1. Noted feet.in fast floving streams in

Burma.

4. SIMMS General Two distinct breeding situs- Chiefly in Strorg prtference ftrTheobald tions varying with seasons, foothills, human blood. Chiefly

During dry season in edges of hills, and found in houses. kestpermanent waters such as mountains. outside by day onlyrivers, streams, and spring- Breeds at when woods reach closefed wells. Dsring wet season elevations to houses. Evei, heavyfound in slow-moving but pro- up to 5,000 raixs will not preventtected water of irrigation feet. In minimus from seeking hosts.ditches and drains of all Tonkin, inci-

sorts. Prefer clean, unpollu- dence ofted water, generally slow- malaria asso-moving with grassy edges. Sel- cdated withdom in rice fields. mininus noted

to inc~reasefroms undula-

ting plainsupward to lowmountains.

A. niaernxims General Shade loving species. Prefer Generalir a PrefeT cattle to man.Giles bodies of water covered with lowland Rarely found in houses,

ves8tation. Swamps, fish species. Will bite ma outdoors Inponds, borrow pits, heavily evening, and in abade

vegetated tacks, edges of during day. Considerzd aslow moving streas, and rice wild species. Man not afields are cmonsi sites. Occa- primary host.sfonally in brackish water.

t

Diurnsa. Pt.dinu Seaso=2l Flight Importance as aPattern Rest Pattern Distrioouticn Range Disease CArr.er

Nocturnal feeder, Rest outside for Moet numerous dur- tfzgbt range Important -llaria carrierusually starting most part. Seldom Lug first half af up to one. in Arakav, along Burma-about two hours iý Isa dwil- year in Burma. Asso- -,-lf mile. Bengal border. Consider~d

af•tcr sundown. inis. cated with pro- second in Importance onlyumosoon rains in to minimas in lItocbina.irikan. Also carrier of •iahkz-

aria bancrofti.

Largely nocturnal Rest ouzside on Active all year Not known. Naturally infected withbut mny feed at shaded atone valls ovwe sach of area. malaria.any tine. and banks. -my Greatest mbars

rest in stables in rainy seasot,.and houses.

Generally noc- Rest outdoors dur- Heaviest concer- Flight range An important carrier oftwurnl feedcr i1 day, usually tration during not known. nalaris in Halayida. Also

in dense shade, rainy months. noted a.% carrier of filar-ia~ic ,isghereria bancroftiand Wucberoria 3.JaR~L)

Blood meals lest after 2 a.m. CoL-inuous through- Flight range A malaria carrier of majoreargly between through deytiA* out the year. Maxi- wore than importance L-, Tdochina

9 p.m. and 2 a.m. hours, largely mus breeding times one-haIf only during epidemic periods.#long stream in Nalaysia in mile. Considered a minor carrierbanks. Seldom March *ad Septem- in Burma. A vector 3f ispor-rest in houses, bar. Well adapted tance in hilly areas of

to dry season. Malaysia. Naturally and expri-mentally nafected with Wu-1werria bencrofti.

90. of blood Rest in daytime Infections scat- Usually 2 Cenaidered the most danger-feeding takes in dark houses tered throughout flight eve- ous malar.A carrier inplace after sid- and buts--ust- year. Highest rage less Southeast Asia. due partlynight. Very ally on dark figures in June, than one- to domesric habits and pre-little activity floors or under January, October. half mile. ference for husen blood. Lomg-

durivg first 2-3 beds or cots in and December in lived species. Possible infec-hours after sun- lower half of Indochina. Periods tor of fillriasis CMucbereriadown. room. Nay rest between rains in _.

outside only Ikr"a.when wr-ods zotachnear houses,

Anytime during Rest by day, Highest incidence Not con- Natural iufct, of malariaevengng, or in usually in well in Nalaya August pletely in Indochina rv t.slayrii.shade durLig day. shaded sitations, to October. known. Possible host fzr f2llriastsPrefer cattle to Mycheroa k a .human blood.

Ii

____ __ - -~_ __ I

TABLE I: •. IISET OF •CUT-EAST ASIA - ANOP4E;.I:E K-)SIAlUTOE.S (Cant'uj

Species Distribution Breeding Situation Elevations Affinity to Man

A. sinensif. General Clean water with emergent vege- Apparently a More frequent In cattleWiedem-ann oation preferred. Basically -. Ide eleva- sheds, but also in houses.

a rice fiele morqjito. Found tion range. Vill b•te man at night z.,din rice fields, lakev svaps, Abundant in in shade by day.borrow pits, grassy 9colr, toothil s.

irrigarion ditches, shillowwells, road drains, ctiserns,and rarely t.n brackish water.

Unsheded situaticns preferred.

A. stephcnsi Noted in Prefers sunlit breeding sites. Apparently a Feeds freely on manListon Burma, In 'irban situations breeds in br,-gd ele- (one of chief carriers

Indochina, artificial =on-ainers such as ,ational in urban centers ofa'.d Malay- wells, cis,.•_,ns, fountains, range. India).s a. tanks, tubs, cellars, reser-

voirs, gutters, tin cans, hol-lows of machimnirv, etc. In

rural areas in poots, stres,seepage banks, and v'w-moving irrigation char,.es.

A. subpictus Noted in Prefers clean, unshaded f.-esh Generally Freqjent houses atindefinitus Indochina water pools, rivers, stream., lowlane nigýWi. Generally prefer(Ludlow) flowiag irrigation channels, species. anime! blood but fecds

lakes, end wells. Rarr.y but Coastal mar- readily on man.

on occasion in brackish water, gins and

Ideal sites with duckweed an. river floodother aquatic herbs. p!aZns.

A. sundaicus Coastal and Prefers mildly saline water in Genernilly Voracious feeders. ,F'.(Rode-waldt) lowland presence of algae. Favorite near tide- in houses and cattle .hiJs.

areas of riter beind embankrients which water mar- Generally scribed a:.S.E. Asia protect ricefields from the gins. How- true house mosquito.

sea, or where mangrove has ever, a

been cleared. Also, where fresh waterlagoons separated from sea by form ofsilting up of river =-ouths. species hasMay breed in waters polluted been found

with sewage. Prefers sunlit as high assites. 3,200 feet.

A. ombrosus Ceneral Prefers slow moving water in Generally Most found in sh*J4d(Theobald) vizgin Jungle, usualiy in low eleva- forest or jungli,, but ma

dense shade. Brown, peaty tions. enter houses wichin rhixstagnant pools, water po,:kets Coastal setting. Fierce biters.along tree roots, springs, plains Hay bite man in houses ordeep lakes, and strongly adjoining ýn dense fores:..

brackish water used for breed- hills ere

ing sites. Sun-fearing i-pecies. commo sites.Also reportedin hill areac.

Diurnal Feeding Seasonal Flight Importance as aPattern Rest Pattern Distribution Range Disease Carrier

Move to feeding Rest inside Relatively wrt Flight range Minor salaria carrier ir. Northsites all through houses and out- Important at rice up L,; 1.6GO Vietnam. Chief carrier in twothe night. In side. Leav. harvest time. Occur yards. Ninoi apid,-nIcs. A carrier ofhouses most num- feeding sites throughout the year. moderate i ance in surma.erous from 10-12 near don. Possible developmental host forp.=. filariasis Cucher.r~a bancrofti

and Wuchereria malyi). Possiblecarrier of Japanese b encephs-litis.

Nocturnal feeder, Rest inside by Breeds throughout Strong Not considered to be vn impor-most artive just day in -mall year. M(ost abua- fliers - tant malaria carrier Ln Southeagtb.fore midnight. dark crevices, dent when rainfall may travel Asia realm. Naturally infected

creases of fairly heavy and up to 3 wit'i Wi.chereria bancrofti.clothing, etc. relative humidity miles.

is high. Latewinter and spring

- show lower infec-S~ticn rates.

Nocturnal feeder. Zest in all types No real predicta- Strong Carrier o! se.cndary importanceof shelters--cow bil.ty from year fi'ers. in Indochinese ares. Possiblesheds, houses, to year. Host fre- Ninrous carrier of filariasts (Wuchereriabuses, tr2min, quent malarial flights b.

I ships, etc. infections in noted ofspring and ant- 04 oneVIND. mile.

Bites moa bj day Rest by day In No real predicts- Strong Chief malaria carr:.er in coactalI as well as at houses, usually bilit7 from year fliers - situations in Southeast Asia.

eight. Tending in rooms In which to year. Moat fre- often over Generally considered second rot to feed on man they have fed. quent malarial in- one mile, A. minimus in all of Sothtast

even in the pr*- factions in spring Asia. Possible infector ofsen-e of cattle, and autm. filariasis (l'cbereria bhncr .I'.

SFeed at night Zest In jungle Little seasonality 71.-,t tene MHala'ie carrier. Not highlylxrgely on ani- vegetation r5.ar of occurrenca. of abour infectious, buz rciti"' s.un-

Mais. In houses breeding sites. &ugust to Decemb•cr 1,000 yards. dance and longevity add toit attacks in Malaysia. danger. Especially importantboldly, even alonag W coast of salaya.under lights.I )(ax~imo bloodieeding between

i i10 p~.end 2 a.m.

p

nl a l II I Il l ~ i 1 1 I I II I

TABLE II: :iARa;L, INSLCTS OF SOUTH!EAST ASIA - WOSVUITOES OTAER THAIn AMOPHELINE

Species Dist.tibution Breeding Situation Elevations Affinity to man

Aedes General Called mosquito of seaports, most common Considered mist domestic

_______ closely associated with human on coastal of wosquitoes. Usually

(Linnaeus) settle.aits. Breeds in all plain, but found within 1500 feet

artificial cullvLl*,, f zl-ýfounz fE human habitation.water, such as rain barrels, up to 10,000 Attacks under coier,

tani2, cisterns, tin cans, feet. ankles, back of neck,urns, and coconut shells, under blankets. Most

Also in tree holes, plant common along cammnicationr;leaves and axils. May breed lines.in fresh, chlorinated orbrackish water, though fresh

water preferred. Often

breeds inside houses.

Aedes General Commnly found to breed in Broad range. Strongly anthropophilic

albopictus artificial collections of From coastal but prefer to bite out-

(Skuse) water near -an. Also found lowlands up doors. Will enter home

in tree holes, rock holes, to 6,000 freely for blood meal.

cu•t bamboo, leaf axils, and feet.coconut shells.

Culex General Sites with clear water in Most wide- Enters houses and readily

biraenio- presence of filamentous green spread in feeds on man. Will Jbite

rhynchus algae preferred. Paddy fields, foothills, in or out of dwellings.

(Giles) agricultural drains, ponds, often insmall lakes and pools, and associationalong margins of mountain with Anoohelesstree&s. Minimus.

Broad eleva-tiou range.

Culex General Larvae usually found near Broad eleva- Strongly attracted to mmn.S fatfeans huma habitation, in drains, tion range Feed actively only at sibht.

Wiedemann cesspools, latrines, shal- Enter houses. Extrewly

low wells, ditches, and _abundant in most areas.

almost any other open water.Can survive a high degree of

_ sali:nity.

Culex Indochina, Breeds to ground pools •-Ith Not noted. Enters houses, viciouoxeiu Burma, Thai- weeds, marshy tracts, swamps, biter.Theobald land, & and other natural collections

(r~liess) malasrim cf water.- z-rpctdirice field, and "hstructeddrains.

C xhailand, Generally a marsh mosquito, Broad eleva- Readil. enters houses during

tritaenio- Burma, and tbund'ntly found in marshes, tion range, evening hours. Feeds LndLs-

rhynchu2 Indochina. swamps and poozly drained crirAinantly on man and larger

(Ciles) flood plains. Also in rice m Imals.fields and ground pools.

Mansonia General Commonly focuod in iresh water Elevational Strongly anthropophillc.

annulifera pools, pondt, marshes, and range not Found in houses at night.

(Theobald) hackwaters. Often in water known.

louled by coconut husks.

Iasonla Burma, Fresh water ponds, poolb, Elevational Enters houses and feeds on

dives Thailand, breakwater swi•ps and marshes, range not man.

(Schiner) and Indo- commonly is aszociated with know.-n.

china emergent vegetation.

rensonLa Buxna, Swamp brebner, larvae often Not known. Females generally anthro-

LnM&EIt•P-!- Tha.iland attached co roots of --amwp pophilic.

(Van der Wuip) and Malaysia tree*. Often found on banksnear rice fields and in ponds.

I

Diurnal Feeding Seasonal Flight Importance as aPattern Rest Pattern %istribution Range Disease Carrier

Bites day and Rest inside ycu;d in all stages Short Chief carrier of denguenight, .y__•-.-- houses on dark of development flight# are fever in all areas.must secure clothing, uxu- throughout the chrsacter- Principal cArrier ofblood seal lme- ally in sleep- year. istic. yellow fever '.•ereyerditely after ring quarters. Rarely disease occurs. Possiblyve mtlng nMost May be active found far a carrier of filariasis.active mrning af any tine, irom place Infector of chikungunya.and even/ing of origin.

hours. Uill notfeed in completedarkness.

Bite outdoors lest most fre- Not specifically Shoort Possible carrier of Jsapneseand most ire- quently in wood- noted, flight B encephalitis, and carrierquently during land. Rast more range, usu- of dengue fever where diseasetwilight hours, at night than in ally no present. Capable of trans-D o n o t b i t e a t d a y . p e e t a a l f i e enight.

more than mitting yellow fever and possi-200 yards. bly filariasis and chikungunya.

Generally noc- Females rest in Seasonality of Fiight Carrier of filariasis (Wuche-turnal. Rarely houses during occurrence not range not rena bancrofti).during day. day, known, known.

NIocturnal feeder. Rest in build- Found all year Long f".ight Carrier of jucheria bancrofti.ings during day. over most of area. range - 3

Highest incidence to 4 miles.in Malay& in Marchand December.

Not known. Not known. Active throughout Not known. Naturally infected with Vuche-such of year; retia maL.a and Wuchererial*ev1est concen- bh.ncrofti. uspected carriertrorions in wet of Japanese B encephalitis.season.

Feed& at any Cenerally rest Createst frequency Flight Ce-erally regarded as the prin-time during indoor* by day. of disease at end range not cipal carrier of Japanese Bnight. Infre- of vet season. known. encephalitis. Reservoir hostsquen.ly duriau

day. are likely birds.

Generally a Rest pattern not Seasonality not Plight Probably the most important carriernocturnal feeder, known, known, range not of _h •_ - (filariasis) in

known. Far East.

Feeding pattern lest Pattern un- Seasonality not Flight Carrier of Luchereria xmlarinot noted, known. known. range not (filcriasis). j* known,

My feed day or Not known. Not known. Long flight Most important carrier of Vucha-night. range. rena alayi in Malaya.

TABLE II: HARMFUL INSECTS OF SOUTLMAST ASIA - MOSQUITOES OTHER 1HAN ANOPHELINE (Cont'd)

Species Distribution Breeding situation Elevetions Affinity to man

14naonia Burma, Indo- Comonly found in pools. Open Elevttiona. Generally mnthropophilic.uniformis china, and terrain preferred over forest. range not Found in houses and out-(Theobald) Thailand. Found rarely ir. mangrove known. side around stables vhere

swamos. cattle and horses are ýept.

Diurna! Feeding Scasonal Flight Importance as aPattern Rest Pattern DListribution Range Disease Carrier

Hay bite cay or Rest among lo_ Seasonality not Long flit:it Important csrrier of Wuchererisnight in houses graving plants by known. range. ma tavi (filariasis).or outside, but day.most often consi-dered a nocturnalfeeder - shortlyafter dusk.

Ii

L a

I

i I

i!

iII *

" {1 .

T•BL III: .LVRMF-'. INSECTS (OTeIdER T7N MOSgUIT )ES) 1. SOU-£HEAST ASIA

General Breeding SItuation and/or* Species Distribution Znvironmentsl Adaptation Elevations Found

Aphiochaera Malaysia Lay eggs in cuts and sorez. Not knovn.scalarisHeigenflesh fly

Chrys,=yia General Deposits eggs only in infections of live tiscue. Broad elevation range.bezziana Ozcurs in vicinity of cattle and other mtr=s ls.Villeneuve Feed on fresh cow dung, flowers, and honey dew.non-biting fly Eggs glued to dry skin over bruises or abscesses.

Occasionally in places soiled by excrement orblood frou wounds. After hatching larvae feednear skin surface for a time and then burrow deeplyinto living tissue.

Chrysov/ia Indochina Commonly breeds in decomposing animal matter, par- Apparently broad eleva-megacephala and Burma. ticularly the dead bodies of animals. Rarely tional range.(Fabricius) Likely in deposits eggs in diseased live animal tissue. May.icn-bitleng fly other adja- deposit eggs in other fo~d stuff."Orievtal blue cent areas.bottle"

ft'sca sorbens General Lggs deposited in horse, cow, or human feces, Broad ranse.Wiedemann especially in single deposits. Comonly foundClose relative on cattle or horses far from human dwellings.of common housefly.

Phlebotomus Noted !n Appears capable of breeding uherever there is War= moist climate upargentipes ln.ochbna unprotected soil high in organic matter. Conta- to 4,000 feet.Annandale and and likely minated ground within 20 yards or so of dwellings,Bru•etti found in or caltl- sheds. Favorite haunta of %dults aresand fly other badly lit cattle sheds and stables, or bathroý=s

areas. of houses. Generally seek to avoid wind, sun, andfull day!Iiht.

Sarcopbaga Indochina Breeds in wide variety of substances incluaing Apparcutly broad range.fuscicauda and Bu.=a. meat and htman excrement. Closely associatedBortcher or Likely in with man. Species oviparous, female givin•ý._pcjLinr adjacent birth to tairly large and active larvae.Robineau- arras.Desvo~dy"Flesh fly"

Sarcuophaga Gencral Oviparous, female givinC birth to active larvae. U'nknrow. - likely broadruficornis !lo.--mally deposited on carrisn,. excre=ent, and on range.Fabricius slightly tainted =eat, and possibly on diseasednon-biting fly body tissues.

Nosopsyllus Indochina Parasitic on vertebrate hostt, chiefly rats and At variable elrvati.is.fasciatus and -hat- nice. Found in zituations attractiva to rats

Bosc d'Antic !dzid. aid nice, Seem to be favorcd by relatively cool

flea odto.

Pulex irritans GeaerAl 3reeo3 freely in all situations occupied by man. Found essentially every-Linnaeus "olerant of wide renge of enviroimental condi- where =an found. Coma--nflea Lions. Man primary host, but found on dogs, in both plains ard moun-

squirrelt, and other arimals. Deposit egos i. tains.clotaUng, on becs. aud in cracks of floors.

N

Seasonalizy of fl.epn. of Role as;.ffirity to Man Occurrence Tranfmission "Disease CarrierI t known. N;ot known. Infect by depositing larvae Infector of ryiasit.

in open wousnd€ rand cut-..

Flies attracted to any dis- Little season- Direct infection by deposi- Chief infector of iyaissis.caarge from infection. In- ality in warm tion of eggs on hnunn host. Appears to be a major prob-flaned eyes a common point moist areas. Eyes chief point of attack le= in all areas of reportedof attack. Cattle chief Areas with cool buJt found on almost every incidence.host. Not cncsonly found seasons will have part of human body - sinuses,in houses, reduction in in- ears, nasal cavities, genital

fection during and rectal areas.cool period.

Comaon market place fly, Seasonally pro- Direct infection by deposi- Infector of secondary impor-especially on meets and nounced only ting larvae on human host. tance of cyiasis. Mechanicalsweets. where there is a Affect eyes primarily, but carrier of bacterial dysentery.

distinct cool also found iv genital areas,aseas-n. nasal cavities, sinuses, ears,

and rectal areas.

Comon household and bazaar Limited to warn Eggs deposited on or near Agent of importance in Lutes-fly. Often settles around season where infected part of hwa.. body, tinal and eye infections."eyes of children, feeding there is a marked or on food later eaten by A possible infector of yaws.on eye discharge. cool season, man.

Feed on cattle when pre- Seaaomality not Infects by biting man and Chief carrier of kale azarscnt--turn to man as alter- known in this depositing parasite in skin, (leishtanla donovani).native. Generally inactive area. or more like.y by crushing -

during day--but may bite at infected insect on skin.rn7 time. Often rest in Bite is quite painful.houses behlnd pictures.clothing or in dark coruariof :oes. Ankles are afavorite po.nt of attack.

Coson in and around oouse- Not known. Infect by depositing larvae Infector of intestinal myissisholds. in food eaten by rmaný of minor importance.

ICoamol around human settle- Not known. Infcct by directly deposi- Associated with dermal ayiasis.

-Cnts. ting larvae on diseased Also reported for intestinaltissue, or by infecting myissis.human food.

Readily attack man In lieu iVot kno--n. Infects by biting van after Plague carrier. One of chiefof natural hc't. :n housee being infected by host agents for maintaining plagueat higher elevations, carrier, in nature. Possibly infector

for m=rine typhus.

Feeds vora:iously on man. No apparent sea- Infects by biting, Likely a plague carrier whereverFollw humen dittribution sonaliry. abundant. Naturally infectedpattern - Lnemn as tLe with typhus.human flea. Rest by dayin rugs. bedding, cracks offloors, etc.

S•, mmea~mmmmmmm m• • ~m mmmmmmm m~mmm •• m•am• I a±•Ju a J u-

TABLE III: Aa.'FUI. UNSECTS (OTVXR TiL-AN MOSQUITOES) IN SO'J•THEAST ASIA (Cont'd )

General Breeding Situation and/orSpecies Distribution Environmental Adaptation Elevations Found

Xenosy.lla General Parasitic on vertebrate hof . Chief hosts are Most outbreaks in lowlandastia Rattus rattus, lUttus concolor, ,md kattus norve- sites, l!kely not due toRothschild =icus. Found in all situations atzracting rats fact that elevation in it-flea such as grain stores, warehouses, ports, and self is limiting factor.

ships. Most numerous along comunications lines.More frequent on ground floor levels in closelyspaced housing.

Xenopsylla Ceneral Parasitic on vertebrate host. Major infestations Most major ontbreak.cheopis associated with rats. Chief carriers include associated with grain(Rothschild) Rattus rattus, Rattus concolor, and Rattus norve- stores, ships, and ports,flea &eus. Found in P11 situations attractive to and most of these at

rats. Infestations appear to lollow river and low elevations. Pro-rail connections. Host anima" ,st have easy bably not a limitingcommunications with outside, factor.

pedctcvlus Found Inhabit man's underclothing, seek body only to Eytremely broad.hum.-nus almost feed. Eggs deposited in clothing, not on bed-corporis every- ding. Neck and armpits cocmon sites. ThriveLinnaeus where man under conditions of human misery, :owding,coon body lo'usz found, lack of fuel and poor bathing facilities. Human

blood the only fool. Not a serious pest inSoutheast Asia because of prevailingly warmclimatic conditions.

Psederus Noted in Found on border.- of partly flooded rice fields; Not known.alternans Indochina, on grassy borders of pondz."Valker especiallybeetle Tonkin

Basin andLaos.

raederus Same. Breed along edges of pools or partly flooded Not ,kIown.f.uscip.s rice fields; uader grass and low bush vegeta-Curtis tion on zloping river banks.beetle

I

Seatsonality of Means of Role asAffinity to Man Occ'urrence Transmission Disease CarrLer

Affinity of carrier to man Highest incideace Depends in part on temper- Carrier of bccondery lmpor-affects relationship of flea during dry season. ature and humidity, and im- tance of bubcn-c .ind wujineto man. Towns and cities Veak from March pact of these on body mois- plague. Suggested vectormost affected, through 'una in ture. Appear to infest man of typhus.

South Asia. wore during dry season.

Relates to affinity of Highest incidence Transfer from ratt to man Considered chief agent incarriers to man, and rats during dry season depends partly on humidity, transmission of bubonicgenerally attrscted to in Burma. Most Animal nortality in infec- plague. Possible carrierhmsn habitations. Towns active Feb-Key in ted arinals is high, fa- of typhus.and cities report highest Indochina. voring a transfer to man.incidence. Ground level Infects by biting san.locations preferr*'.

Found only on vr -..car man. More widespread By biting infected host, or Carrier of epidemic typhus,Man the only host for epi- in cool season sore likely by infections and possibly of relapsingdem-'c typhus. when more cloth- through contact of feces fever.

ing. with skin abrasion, or byinhaling dried feces oflice.

Enceru houses. Attracted Found entire sea- Blisters caused by body Skin vesicant. Generallyby artificial l.ht. son on borders of fluids when beetles crushed not a serious reaction,

partly flooded on skin. limit to epidermis.rice fields.

Enter houses in May and Not knowz. Sme. oae.September. Occur through-out ytar. Attracted byartificial light.

17

I.I4 l ~ l ll IIl H,,

TIBLE 1V: HLARFUL ARTHROPODS (OTHER THA1N INSECTS) IN SOUTHEAST ASIA

_ eneral Breeding Situation and!orSpecies Distribution Environmental Adaptation Elevations Found

Haeoc:sysalis Indochina Caomon in rich evergreen forest cover, heavy Elevations in IndiaspPivra undergrowth. Rainfall average in excess of 80 range between 1,800 andNeu :: in. where tick is ccwmonly found. Natural hosts 2,000 feet.

tic- are monkeys, rats, squirrels, and man.

Rhiyrz-Zzohalus General Females can mate only after blood meal. Eggs de- Not known. Likely broad

Lsfnrt.•,,!uS posited on ground. Larvae attaches to host - dog range.(Latrr' le) or man. Dog princital host. Attacks man morebrown •>g tick often under hot, dry conditions.

LUwnyoo sus General Parasitic on rats. Often turn to man after rat Broad range. FollowbacoLi hosts eliminated by poisoning or trapping. pattern of rat infestations.Hirst Cos'on in areas of natural rat harborage. Requiresmite four blood meals to complete life cycle.

Trombicula General Most coon hosts are Rattus flvioectus yunna- Broad range - up oakamushi nensis and a tree shrew, Tupai• belangeri 3,000 feet.(Brumpt) versura Eggs laid or ground and hatched larvAemite P.ttach t.Letelves to animals frequenting area.

Man occasionally an accidental host. Parasiticonly in V 4t stage after hetching. !refer riveredges in land periodically flooded.

Trombicula Gene.al Most comon hosts are Yunnan buff-breasted ret Greatest exposure justdeliensis (Rattus flavipectus yunnanensis) and Slader's above sea level. T. de-Walch roof rat (Rattus rattus sladeni). Most cownonly liensis reported up to-mite found in the rural situations favoring a concen- 8,000 feet. Infections

tration of rats such as village garden sites, from them to 7,000 feet.abandoned food dumps, neglected coconut planta- Quite abundant in northerntions, and heavy savanna grasslands. Scrub uplands of Burma.typhus outbreaks accompany drought, flood, poorcrops, famines, filth, over-crovding, and militaryoperations. Hosts apart from rats are often treeshrews, birds and man. Prefer river edgas in landthat is periodically flooded.

5SR12pendra Indochina Eggs laid during cooler season. Deposite- in Broad elevational range..ngulata and other burrows in soft rotted wood. Adults often foundceti pede likely under stoves, bark, under matting in unfloored

areas, houses. Occupy dc-k, damp places. Distinctpreferences for high huzidlties. Most abundantin wet forest situation. Often found in ware-houses in port cities.

Otostiamus Indochinese Occupies dark crevices. Burrows under rocks, Not known.anuleatus area logs, mats, etc. Nocturnal activity.

lasaemillipede

........

Seasomality of Means of Role asAffinity to Man Occurrence Tranmistion Disease Carrier

Ticks infect men opera- Rare during wet Transmission of disease by Ca.rier of Kyasanur Forestting in forest, monsoon. Peak biting. Commonly transmit- disease.

months are March ted from animal to man.and April.

Man comnonly attacked Most pronounced Pathogen multiplies in rick. Importamt carrier Gf tickbecause of close rela- at beginning of Man innoculated by bite of borne typhus, Indian ticktionship between man and rainy season, tick. typhus, and other rickettsialdo'. fevers. Possibly tick paralysis.

Parasitic on house infes- No known season- By biting man. Parasitic Possible transmitter of murineting rodents and may ality. Other mites on rats cnd mice infesting typhus. Bite produces v'si~culrattack man. have lower inci- %,ousts. dermatitis. May be intermediate

dence during dry host foi microbe carriers ofseason. tularemia.

Follow generally the pat- No absolute rea- Infect by biting. Disease Carrier of scrub typhur. (Taut-tern of rat population. sonality. Subet- carried by mites from in- sugamushi disease) second inHighest incidence where- dence appears to fected host to man. importance to _. deliensis.ver food and harborage occur in dry sea-for rats are found. Often son. Mit.es sensi-found in jungle and rein- tive to low humi-forest far removed from dity. Highestman. Active in early illcidence at be-*morning. ginning and end of

monsoon season.

Influence on man depen- No uniform season- Infect by biting man. Pas- Most Important carrier of scrubdent largely upon affi- ality of occur- sage of mites from rats to typhus (Tsutsugaishi disease)nity of carrier to mm. rence. Highest man takes place whenever in Southeast Asis.

As man provides harbor- incidence in the two occupy the sameage for rats the inci- spring and autumn area. Infections tend todence increases. More at beginning and follow drainage lines.comonly rural settings end of vet moo-affected. Active in soon. C.ase Inci-early morring. dence in Burma

noted to subsideduring dry period.Mites appear highlysensitive tolowered humidity.

Not especially attracted Long-lived--up to By biting or stinging with Skin irritant (vesicular derma-to man. May bite or sting 6 or 8 years. In- poisoned claws. title.) Bite reportac on occa-when provoked. Poisoned actike under cool siom to ceaze painful swallingclas mea) irritate skin, or very dry condi- vith real discoafert.

tions.

Pest in houses durinf Maxitmm oc.currence On touch emits a phospho- Skin vesicant. Not a seriousperioJs of hot weather, in stsex , rescent vesicant which reaction.

causes a painful blisteron skin.

F

UnclassifietLSecurity Classificstion

DOCWENT CONTROL DATA - R 8,D(Soewity classification of tSit body' of &bstre t Rozd lnd~rog annotation m~ust at mt~rd when, ti.a o~a.:.!= tpor ciao9SiiqSORIGINATING ACTIVITv (Colpo¢Mt* ,dt•) a&. AEPORT SECUIqlvY CLASSIFICATION

UnclassifiedU.S. Army Natick LaboratoriesNatick, Massachusetts

A. REPOflT TITLE

Environmental Conditions Relating to Harmful Insects of Mainland Sotuhea~t Asia

4. OESCRIPTIVE NOTIES (? . o forort and incluslv* dares)

S AUTHORISI (Pirst nalM., w.IdeI ini? 5*?iaei nam.)

Edgar Bingham

S. REPORT DATE 76. TOTAL NO. OF PAGES No. OF NEWS

October 1968 61 745. CONTRACT OR GRANT NO. *d. ORIGINATOws naPORT mUmveRiSo

b PROJECT NO. 1T062109A129 69-28-ES

c. 4. OTINER REPORT NO(S) (Aft O*" haftbers &at• a be "signefr.dWoe seio)

d ES-40O10. OISTRIIUTION STATEMENT

This document has been approved for public release and sale; its distribution isunlimited.I•'- SUPPLEMENTARY NOTES 17. SPONXSORING MILITARY ACTIVITY

U.S. Army Natick inboratoriesNatick, Massachuse:ts

IS. 41I•TRACT

T•Tid study illustrates the relationships between physical and cultural environments andthe presencc of harmful insects and other arthropods in mainland Southeast Asia. Theserelationships are graphically portrayed in diagrammatic cross sections through variousparts of the study area. In addition, the physical and cultural factors that contri-bute to the propagation and spread of harmful insects are analyzed, and there are briefdescriptions of the offending species. --n---

Of the insects that contribute most to the origin and spread of disease, the mos-quito easily takes first place. The hot, humid climate of Southeast Asia and the numer.ous water bodies provide ideal conditions for the survival of this group of inscc~s.

Various mosquito species are known to be transmitters of malaria, dengue fever, filari-

asis, and Japanese B encephalitis. Other important disease-causing insects includenon-biting flies, fleas, sandflies, and lice, while disease-carrying species are alsofound among the mites and tickst- They are responsible for the spread of a wide varietyof diseases and infections, inclu~ing wyiasis, plague, typhus, kala azar, yaws, andbacterial dysentery.

The principal environmental types in Southeast Asia are: (1) cities and largetowns; (2) villages and isolated rural settlements; (3) ricefields; (4) brackish coastamargins; (5) delta plainE, coastal plains, and floodplains; (6) elevated plains, lowplateaus, foothills; and (7) hills, mountains, and dissected plateaus. Each of theseenvironments has its own complex of harmful insects. In general, the areas of lowestelevation, hiphest rainfall, and liast population have the widest variety of harmfulinsects; and the areas of highest elevation, lowest rainfall, and densest populationhave the fewest. However, there aie exceptions to this rule.

SDD,.. 1473 ..... '. .. "nlas--eSOCsIto0 CsSet.Unlas fied

r!

Unclassified

36curity t~~!f.~ii ______ ______

14 .I LIK A LiNK & LINIK Cnet jORDS ROLE El ROLE W, ROLE WT

Ecology 7

Insects97

Arthropods 9

Mosquitoes 9 7

Disease vecto-s 9 7

Southeast Asia 9 9

Environm~ent 8 6

Terrain 6

Climate 6

Vegetation 6

"I I

I7f

Unclassified

I IFlo

,,. ,, ,, , ,, , •