introductory logy

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INTRODUCTORY ENTOMOLOGY A. THE PHYLUM ARTHROPODA 1. General Characteristic The Phylum Arthropoda is the largest phylum in the animal kingdom. With almost a million species there are more arthropods than all kinds of plants and animals combined. Not only are there great numbers of species in the phylum but many species are represented by countless numbers of individuals. Members of the Arthropoda are segmented animals; that is, their body parts are serially repeated along a longitudinal axis. Collections segments may be grouped into discernible body region such as well- developed head which usually bears compound eyes, thorax, or cephalothorax and abdomen. Another distinguishing characteristic of arthropods is their chitinous exoskeleton . The exoskeletons serve as a protective coat of armor without sacrificing mobility. In addition to serving as protective coat and as a surface for the attachment of muscles it has made possible for the arthropods to live on land. Land life for any kind of organism requires a relatively impermeable outer covering to prevent desiccation and the arthropods exoskeleton certainly does this. Another most conspicuous feature of arthropods are the jointed appendage and it is this characteristic which give the phylum its name. the success of arthropods is in large measure due to the wide variety of adaptive uses of the appendages. Not only did they serve as waking legs, they became modified for swimming, breathing and reproductive activity. They also produced specialized structures which are used in

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Page 1: Introductory logy

INTRODUCTORY ENTOMOLOGY

A. THE PHYLUM ARTHROPODA

1. General Characteristic

The Phylum Arthropoda is the largest phylum in the animal kingdom. With almost a million species there are more arthropods than all kinds of plants and animals combined. Not only are there great numbers of species in the phylum but many species are represented by countless numbers of individuals.

Members of the Arthropoda are segmented animals; that is, their body parts are serially repeated along a longitudinal axis. Collections segments may be grouped into discernible body region such as well-developed head which usually bears compound eyes, thorax, or cephalothorax and abdomen. Another distinguishing characteristic of arthropods is their chitinous exoskeleton. The exoskeletons serve as a protective coat of armor without sacrificing mobility. In addition to serving as protective coat and as a surface for the attachment of muscles it has made possible for the arthropods to live on land. Land life for any kind of organism requires a relatively impermeable outer covering to prevent desiccation and the arthropods exoskeleton certainly does this.

Another most conspicuous feature of arthropods are the jointed appendage and it is this characteristic which give the phylum its name. the success of arthropods is in large measure due to the wide variety of adaptive uses of the appendages. Not only did they serve as waking legs, they became modified for swimming, breathing and reproductive activity. They also produced specialized structures which are used in defense, food procurement, chewing and sensory perception.

Unlike some lower form of animals, which are radially symmetrical., arthropods are bilaterally symmetrical. Their body, if cut along a o

Longitudinal axis, will be divided into two equal halves causing each half to be a mirror image of the other. Also, the coelom in the adult is much reduced and replaced as a perivisceral space by the enlargement of the haemocoele.

2. The Classes of Arthropods

There are 4 existing groups of arthropods; the myriapods, the crustaceans, the arachnoideans and the insectants.

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a. The Myriapod Group

The myriapod group includes arthropods which exhibit many differences in basic structure but share many superficial resemblances. They have centipede-like shapes, a distinct formed the original prostomium and several body segment whose appendages became the mouth parts, an elongate trunk region bearing segmented walking legs, and a well-developed antennae.

a1 Class Chilopoda (Centipedes)

Body elongates dorso-ventrally, head with one pair of jaws; one pair of antennae; two pairs of maxillae, the first pair forming a lower lip; eyes simple, compound or absent. The first pair of body appendages is modified with a sharp poison claw at the tip. The rest of the body segments numbering from 14 to over 10, each with a single pair of legs.

a2 Class Symphyla

Head posses long antennae and the mouth parts consists of mandibles, maxillae and labium. They are about ¼ inch long and centipede like in form. The 15 segments composing the trunk are not fused in pairs of which 11 or 12 bear legs.

a3 Class Diplopoda (Millipedes)

Body segment, except a few at each and of body, fused into pairs so that each apparent segment has two pairs of legs. Body long and usually cylindrical with a distinct head and trunk. Head with many small simple eyes; one pair of antennae, mandible and maxillae. The maxillae are usually fused to form a plate like guathochilarium. Thorax of four segment the first of which is legless while each of the other thre have a single pair of legs. The abdomen makes up most of the body with up to100 or more segments, each of which bears two pairs of legs.

a4 Class Pauropoda

The body consist of 11 to 12 segments, of which the dorsal portions are fused in pairs; eight or nine segments each bear a pair of legs, each pair evenly spared from the next. Head with a pair of eyes represented only by a small spot; antennae biramons. The mouth parts consist of a pair of mandibles and lower lip believed to be the same as the guathochilarium in the Diplopoda.

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b. Class Arachnida

The typical arachnoid have the body divided into two regions, the cephalothorax and the abdomen. The cephalothorax of the adult morph usually bears six pairs of appendages, the anterior chelicerae, the pedipals which are often chelicerae, and four pairs of walking legs, the segmentation of the abdomen may or may not be apparent external and bears no jointed appendages.

c. Class Crustacea

This class includes a varied assortment of forms which are mostly aquatic in habit and made respiration. Majority of the members have the following characteristics; body usually divided into three regions; head and thorax often closely joined and referred to as the cyphalothorax ; two pairs of antennae; and in some forms, four pairs of accessory feeding appendages which includes two pairs of maxillae, and a pair of maxillipeds; thorax usually consist of four to twenty distinct segments, each with a pair of segments, with short appendages or none. Some of the parasitic and sedentary form exhibit extreme reduction in both body segments and appendages. Several forms have a carapace covering a large portion of the body, others have shell and look like bivalves.

d. Class Insecta

The body has three distinct regions; head, thorax and abdomen; head bears eyes, both simple and compound, and one pair of antennae (except Protura); three pairs of legs borne by three-segmented thorax (a few are legless, and some large posses additional leglike appendages, such as prolegs, on the abdominal segments; often one or 2 pairs of wings, borne by the second and/or the third the thoraxic segments. The postoral appendages of the head typically consisting of a pair of mndibles, a pair of maxillae, a Hypopharynx, and a labium).

THE GENERAL STRUCTURE OF AN INSECT

THE BODY WALL

The insect body wall or exoskeleton consists of three principal layers; an outer cuticle containing a nitrogenous polysaccharide, chitin, proteins and usually pigments; the outer cell layer of the insect, the epidermis, that lies beneath and secrete the cuticle, and the basement membrane a non cellular layer up to 0.5 thick beneath the epidermal cells.

The cuticle covers the whole of the outside of the body as well as the inner walls of the foregut and hindgut and the tracheae. It is differentiated into two principal parts,

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the epicuticle, a thin layer containing no chitin and is only 1-4 thick; and an inner region which contains chitin and forms the greater part of the cuticle. This chitinous cuticle is known as procuticle as it is first secreted, but subsequently the outer part becomes harder than the rest to form the exo-cuticle while the inner portion remains undifferentiated and is now called endocuticle. The exocuticle and edocuticle are traversed by minute pore canals which extend up to the epicuticle during its early formation to allow various substances including waxes to pass through. In this way the epicuticle is coated and waterproofed.

The hardened surface of the insect body form plates called sclerites, which are separated by membranous areas known as sutures. Sutures permit movement of the various parts of the body and its appendages. The principal sclerite on the dorsum of an abdominal segment is called the tergum (pl. terga) and on the thoracic segment, and on the thoracic segment, notum (pl. nota). The main sclerite on the center of a body segment is the sternum (pl., sterna) and that of the lateral area, the pleuron (pl., pleura).

The external and internal processes are found on the body wall. The external processes sucs as scales, spines and setae, may be of solid cuticle, some contain all three body layers, while still others are outgrowth of individual or several epidermal cells. The internal processes are infoldings of the body wall which strengthen it and serve as muscle attachment; some are ridge-like whileothers are spines like.

THE INSECT HEAD – This is the anterior heavily scleritized capsule-like body region that bears the antennae, eyes and mouth parts. It can be likened to a mammalian skull that protects the vital parts of the nervous system and the sense organs.

Most insects have both simple and compound eyes. The relatively large compound eyes are located dorsolaterally on the head and between them on the upper part are the three simple eyes or ecelli.

THE ANTENNAE – the antennae are usually situated between or below the compound eyes. The vary greatly in size and form and are frequently used in classification. Typical antennae consist of a basal segment called the scape; the second segment, the pedicel; and the flagellum or remaining segments. The antennae are sensory in function and act as organs of smell, hearing or touch.

THE MOUTH PARTS – The insect mouth parts are variously modified in different insect groups and are much used in classification and identification. Typically, the insect mouth parts, consist of a labium or upper lip; a pair of heavily scleritized jaws lying behind the labium; a pair maxillae; and a hypotharynx, a short tongue-like structure located between the maxillae and above the labium.

There are two general types of insect mouth parts, the mandibulate or chewing and haustellate or sucking.in insects with mandibulate mouth parts, the mandibles can

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move sideways and the food is bitten off chewed. Insects with haustellate mouth parts have these in the form of elongated proboscis or break through which liquid food is sucked. These two general types of mouth parts vary considerably in different insects; these variations are given subsequently.THE MANDIBULATE MOUTH PARTS – This is considered the more primitive and is found in the adult of the following orders; Thysanura, Diplora, Collembola, Orthoptera, Dermaptera, Psocoptera, Mallophaga, Odonata, Plecoptera, Isoptera, Neuroptera, Mecoptera, Tricoptera, Coleoptera and Hymenoptera. It also occurs in the larval stages in many insects.

In a few insects such as bees and larvae of Nyeuroptera their mouth parts are described as chewing-sucking; the labium, maxillae and mandibles are modified into tongue like structures through which liquid food is sucked.

THE HAUSTELLATE MOUTH PARTS – This type of mouth parts has eight principal variations and occurs in the following groups of insects:

1 ) Thysanoptera, 2 ) Hemiptera and Homoptera, 3 ) lower Diptera, 4 ) the Asilidae, 5 ) Higher Diptera, 6 ) Siphonapteram, 7 ) Anoplura, 8 ) Lepidoptera.

THE THYSANOPTERAN MOUTH PARTS – the mouth parts of thrips is asymmetrical and have been called rasping-sucking. Some of the parts have become rudimentary leaving only three functional stylets: two maxillary and the left mandibles.

THE HEMIPTERAN MOUTH PARTS – In the heteroptera, the proboscis arises infront while the labium which forms a sheath, enclosing two mandibulan and two maxillary stylets. The maxillae fit together forming two channels: a food and salivary channel. The other structures of the mouth parts are either reduced or wanting.

THE MOUTH PARTS OF LOWER DIPTERA – The lower Diptera include the mosquitoes, black flies and house flies and are otherwise also called listing flies. In these insects, the labium, mandibles, maxillae, and hypopharynx. The mandibles as wanting and the principal piercing organ is the hypopharynx are stylet-like. They encloses these six stylets and do no piercing.

THE MOUTH PARTS OF ASILIDAE – these insects have four stylets, the labium, maxillae, and hypopharynx. The mandibles as wanting and the principal piercing organ is the hypopharynx.

THE MOUTH PARTS OF THE HIGHER DIPTERA – there are two modifications of the mouth parts of higher Diptera namely; the piercing type and the sponging or the lapping type.

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The piercing type occurs in tsetse flies, horn flies, stable flies and house flies. The labium and hypopharynx are slender and stylet-like lying in a dorsal groove of the labium is the labella, a pair of small hard plates armed with teeth. Between the labrum and hypopharynx is the food channel and salivary channel is in the hypopharynx.

The sponging or the lapping type occurs in houseflies, blow flies and house flies. The proboscis is made up of the lower part of the head called the rostrum and the haustellium which is formed by the labium. The structures of the mouth part hang from the rostum and the maxillary palpus arise at its distal end. The groove of the labium receives the slender hypopharynx, which bear the salivary channel, and the labium between which the hypopharynx lies the food channel. The labium terminates in a pair of large, oval lobes, the labella. The lower surface of the labella bears numerous transverse grooves, which serve as food channels. This type of mouth parts lap up food which may be already in liquid form or still solid but first liquefied by salivary secretions.

THE SIPHONAPTERAN MOUTH PARTS – the mouth parts of adult fleas consists of three piercing stylets, namely; the epipharynx and the laciniae of the maxillae. Adult fleas are blood suckers but their larvae feed on organic debris and have mandibulate type of mouth parts.

THE ANOPLURAN MOUTH PARTS – the mouth parts of sucking lice has an eversible rostum from which produces three piercing stylets; the dorsal stylet, which probably represents the fused maxillae, had its edges curved upward and inward forming a food tube; the slender intermediate stylets containing the salivary channel which probably represents the hypopharynx; and the ventral stylet or principal piercing organ which probably is the labium.

THE LEPIDOPTERAN MOUTH PARTS – Insects having this type of mouth part do not piercing but merely suck or siphon liquid up through the proboscis. This structure is uncoiled by blood pressure and recoils by its own elasticity. It is made up of two galeae of maxillae which come together to form the food channel. The labium is a mere transverse sclerite across the lower margin of the face. The labial palps are well developed but the maxillary palps are either reduced or wanting. The mandibles and hypopharynx are lacking.

THE THORAX – this is the region of the body after the head to which it is connected by a membranous neck region called the cervix. In most adult insects it is usually bears three pairs of legs and two pairs of wings. The thorax is divided into three segments: the prothorax, mesothorax, and metathorax, the last two are usually known as the ring-bearing segments. Each thoracic segment is like a box composed of four groups of sclerites: the norsal notum, the two lateral pleura and the ventral sternum.

THE LEGS – Fully developed and functional wings may be present in immature stages. The wings appear as thin, rigid flaps arising dorsolaterally from between the pleura and

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nota of the wing-bearing thoraxix segments. Each wing consists of thin membrane supported by tubular veins. The wing membrane is formed by two layers of integument closely apposed and the veins are formed where the two layers remain separate. The up and down movement of the wings are produced by muscles and the elasticity of the thorax, the wing bases and the muscles themselves. THE EBDOMEN – this region of the insect body typically consists of eleven segments but the last segment is usually much reduced so that only ten are more or less apparent. Fusion of segments or telescoping of the more posterior segments may occur in many insects.

Each abdominal segment consists of two sclerites, a dorsal tergum and a ventral sternum; the pleura is the membranous area in between.

Abdominal segments 1 to 7, called pregenital segments bear appendages in various immature insects, in adult aptrygotes and male odonate but are usually lacking in most adult insects.

The genital segments, 8 and 9 may bear the structures associated with reproduction.

METAMORPHOSIS – Metamorphosis can be defined physiologically as the change which accompanies a molt in the absence of juvenile hormone (Chapman 1969). Snodgrass (1945) relates it to the loss of adaptive features peculiar to the larva.

Insects can be grouped into three categories, the metabola, the hemimetabola, and the helemetabola, according to the extent of change occurring at metamorphosis. The ametabola includes the Apterygota which have no metamorphosis. The adult morph resulting from a progressive development of the larval morph. The larva emerging from the egg essentially resembles the adult except for its small size and the absence of developed genitalia.

The hemimetabola includes the orders Orthoptera, Isoptera, Heteroptera and Homoptera. In these insects, the larvae hatch in a form which generally resembles the adult apart from their small size and lack of wings and genatalia.

The Plecoptera, Ephemeroptera and odonate whose aquatic larva undergo a more conspicuous change, in adaptation and breathing structures are also regarded as holometabolous because the general body from resembles that of the adult.

The orders Neuroptera, Trichoptera, Lepidoptera, Coleoptera, Hymenoptera, Diptera, Siphonaptera, Thysanoptera, Aleyrodidae and male Coccidae are holometabolous. In these groups the larvae are quite different from the adults and a pupal instar is present between the last larval instar and the adult.

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BEHAVIOR – the actor or patterns of behavior of insects are responses to various stimuli. Many of these so called directed responses consists of orientation ( tropism) and movement (taxis) toward (positive) or away (negative) from the stimulus. Stimuli, such as light, temperature, water, chemicals, touch or contracts, force of gravity, or current of air or water, produce directed responses in insects.

Many insects have very specific responses to light; some such as lepidopterans, go toward light, while others, such as roaches, bedbugs and mosquitoes, avoid it. The ability of insects to locate food, mate or site of oviposition is due to their positive responses to certain chemicals. In the case of tacticle stimuli, insects respond negatively; on the other hand the squeezing into small openings of the crevices of insects such as roaches and bedbugs is a positive response to certain tacticle stimuli. Dragon flies flying headed into the wind show positive orientation response to air currents. Aquatic insects heading or swimming upstream exhibit a positive response to water currents.

A knowledge of insect behavior is one of the keys to the proper control of insect pest population.

The Orders Of Insects

The orders of insects fall into two groups or sub-classes:

Sub – Class I - APTERYGOTA

Members of these subclass are quite separate from the rest of the insect order in that they are apterous or wingless descended from wingless ancestors. Their primitive features are not insectans at all but they do have three distinct body regions and three pairs of legs. These characters justify retaining them in the class Insecta. The apterygotes are placed into four orders:

Order – 1 DIPLURA (Campodeans or japygids)

There are usually pale colored insects with two caudal filaments; compound eyes absent; mouth parts mandibulate and more or less withdrawn into the head.

The young and adults differ chiefly in size and sexual maturity. They occur under leaves, stones, logs, or debris or in the soil. Their movements are slow and they are negatively phototrophic. None of the species is of economic importance which explains the lack of studies on their biology.

Order – 2 PROTURA (Proturans)

Proturans are minute, slender, whitish insects. The cone-shaped head has no eyes and antennae, mouth parts consist of stylet-like mandibles, small simple maxillae and a

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membranous labium. The three pairs of legs are similar with the first pair serving as tacticle organs and curved like an antennae.

These insects exhibit anamorphosis or adding segments to the body at each molt. The nymphs and adults are similar in general appearance. They live in damp homes and soil, feeding on decayed organic matter.

Order – 3 COLLEMBOLA (Springtails)

These are minute insects with a characteristics ventral jumping organ called furcula coupled with a button-like structure called tenaculum.

The young and adults are similar in appearance and habits, differing primarily in size and sexual maturity. They are found abundantly in moist habitats. Their biology is practically not studied.

Order – 4 THYSANURA ( Silverfish, firebat)

These are moderate-sized to small insects, elongate with shape with three tail-like appendages at the posterior and of the abdomen and style-like appendages on some abdominal segments. The paired tail-like appendages are the cerci and the third, the median caudal filament body covered with scales.

Thysanurans lay their egg singly in cracks, crevices and secluded places. The young grow slowly, attaining maturity in 3 to 24 months and having a large and indefinite number of molts. Molting continues after the adult stage is reached. They feed on all sorts of starchy substances and frequently become pests.

Sub-Class II – PTERYGOTA

Members of this subclass are the true winged insects, some of which have in fact become secondarily wingless. The pterygotes fall into two main divisions, the Exopterygota or Hemimetabola and the Endopterygota or Holometabola.

Division I – Exopterygota (Hemimetabola)

These are called exopterygota because in their young stages the rudiments of the wings are visible as small projections on the outside. Alternatively they may be called Hemimetabola, a name which refers to the fact that is, they undergo a comparatively mild metamorphosis or change when they pass from the larval stage to the adult. These young larval stages, which commonly live a life like that of the mature insect are often termed nymphs but may also be referred to simply as larvae.The Exopterygota fall into two series, namely:

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Series I – Paleoptera or ancient winged insects. These are the earliest winged insects. Many had their wings permanently extended on each side of the body, or held erect above the thorax. They are unable to fold the wings back over the abdomen when at rest. The two surviving orders are:

Order 5 ODONATA – Dragon flies, damsel flies. The head of these insects is often occupied by the large many-faceted compound eyes, antennae small and bristle-like. The wings are elongate and many veined. The abdomen is long and slender; the one segmented cerci function as clasping organ in the male.

The female members of this order lay their eggs in or near the water in different ways. Some thrust their eggs into aquatic vegetation or rotten wood; others deposit their eggs in masses on objects beneath the water surface, or lay in ribbons or rings in the water or burry into wet mud near the water’s edge in many species the female dip down to the surface and work the eggs off the end of their abdomen. Still others crawl beneath the water to deposit their eggs.

Development may take a year for smaller species and 2 to 4 year in the case of larger species. The full grown nymphs crawl out of the water and attach to a stick, stem or other object for the final molt. The newly emerged adults are soft becoming hardened and colored in 1 or 2 days.

The nymphs are aquatic and like the adults are predaceous on other aquatic insects and crustaceans.

Order 6 – Ephemeroptera – May flies are small to large, slender, soft-bodied insects which are hemimetabolous. Adults have two pairs of net-veined wings, the second pair small or completely reduced in some general; antennae hair-like; eyes prominent and abdomen with a pair of very cerci and usually a median terminal filament.

The female releases masses of eggs from the abdomen, dives into the water and releases the eggs into it. These eggs hatch in a few weeks or a month depending on the species. The nymphs are aquatic with well-developed chewing mouth parts and usually a series of tracheal gills on the abdomen. When fully grown they swim to the surface of the water or craw up on some support, the winged from emerging from the nymphal skin. This winged form is capable of flight and looks like an adult mayfly but is sexually immature. This is called the subimago stage which molts into the mature adult.

Series II – NEOPTERA

Order 7 Dictyoptera (Mantids, walking sticks and Cockroaches) – Members of this order include wingless, short-winged, and long-winged forms. The winged members have leathery fore wings and a larger membranous hind pair: Mouthparts of the chewing type, metamorphosis simple. The almost of the same size legs are fitted for running.

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Cockroaches have unusual egg laying habits. As the eggs pass the oviduct to the egg chamber they are glued together by a secretion into a capsule or ootheca. The capsule is formed over a period of several days. The hatching process is different in different species. In some species it is deposited long before hatching; in others, it is extruded but one end is attached to the brood chamber and carried about until hatching time or it is retained within the brood chamber until the eggs hatch there and live young instead of eggs come out.

Growth in the nymphs is relatively slow but they are very active. They may attain maturity in a few months but in some species a year or more is required.

Cockroaches are one of the most obnoxious pests of human habitations. They get into many kinds of food, clothes, books and newspaper closets, eat part of these materials, discolor and spot them with fecal material and leave behind disagreeable odor.

Preying mantids are medium to large size insects, having an elongate prothorax and large spiny front leg used for grasping. The middle and hind legs are smaller and usually slender. The wings may be long, short or wanting. Many species are green, brown or mottled but a few are brightly colored while still others have definite patterns.

Mantids are predaceous in habit. They feed on other insects which they seize by means of their highly prehensile front legs. Many mantids are cannibalistic, in fact in certain species it is usual for the female for the capture and eat the male after mating is completed.

The eggs are laid in a definite pattern and in large masses and glued together into an ootheca. An ootheca is glued to a branch or to some other object. The biology of this group of insect is not well-known.

Phasmids are small to large sluggish insect which mimic leaves or sticks. Their resemblance to leaves or sticks has earned for them the names “leafsticks” and “walkingsticks”, respectively.

These insects are generally leaf feeders and most of them are three dwellers. They may defoliate large areas of woodland when occurring in large numbers. They have the habit of playing opossum if disturbed.

It is presumed that the eggs are laid singly and simply dropped to the ground where they hatched after sometime. The biology of these insects in the Philippines is not known.

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Order 8 – ISOPTERA (termites, white ants) - Isopterans are medium-sized social insects having several different social castes. A typical colony may consist of reproductives, sterile workers and sterile soldiers.

Termites feed on cellulos obtained dead wood. Colonies are located in dead trees or logs or in the ground with covered runways connecting the nest to the source of food supply. It is the sole duty of the workers to forage for the colony and feed both the soldiers and reproductives. The soldiers protect the colony from enemies, staying at strategic points near the exits of the colony. The reproductive maintain the species by producing eggs almost continuously, but it is the workers that take care of the eggs until they hatch.

During most of the year only soldiers and workers are produced but winged females and males are produced in intervals. These fully formed reproductive individuals leave the nests in swarms, disperse, mate and found new colonies. A single pair of reproductives founds a new colony. They lose there wings after the nuptial flight and together build a nest in a dead stump or log. They fend to provide for oneself for themselves and the female produces eggs which develop into workers and soldiers. When the workers and soldiers have matured they take over the activities of nest expansion and the feeding and protection of the reproductives and the larvae. If either of the reproductives dies, they are replaced by worker-like fertile forms called second reproductives.

Termites cause a considerable amount of damage to buildings. Termites invade buildings through weed foundations and spread from this point into upper parts of buildings. They cross nonwood areas by building covered runways out of excrement, soil, and chewed wood and by this means derive much needed moisture gain access to other wood parts of buildings, books and furniture.

Order 9 – ORTHOPTERA (grasshoppers, locust, crickets and katydids) – Orthopterans are medium-sized to large insets. Many of the members of this group have the hind legs long, their femora enlarged for jumping. The head is large with usually long thread-like antennae, well-developed eyes and mandibulate mouthparts. The pronotum in many forms is large and produced downward at the sides forming a large functional wing, the fore wings or tegmina are invariably leathery, and the hind wings membranous and fan-shaped when spread. Other species are short-winged or completely wingless.

The locusts or grasshoppers are herb feeders, but a few feed on the leaves of trees. The eggs are laid in masses in the soil. To this group of insects belongs the migratory locusts which periodically develop into enormous populations that staggers the imagination. They migrate in swarms traveling many hundred miles denuding all areas along their path and resulting in complete destruction of farm crops. The other members such as katydids, crickets, and pygmy grasshoppers are less economically important.

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Order 10 – DERMAPTERA (earwings). These are heavily selorotized medium- sized, elongate insects with forceps-like cerci at the end of the abdomen. The front wings are short and leathery while the hid winged are membranous and fan-shaped. Some species, however have no wings. They are omnivorous in food habits and are nocturnal.

The eggs are laid in a chamber in the ground and the female watches over these until hatching time and at least for a short period care for the young earwings. The young molt for to six times, attaining maturity in a short time.

Some species become pests of great importance in gardens and in the home.

Order 11 – EMBIOPTERA (Webspinners) – these are flattened elongate insects with enlarge front tarsi which are used for spinning webs in which they live. The females are always wingless but the males usually have two pairs of long membranous similar wings with very few veins.

Web spinners feed on various plant materials, especially dried grass leaves. Their silken tunnels may be found under loose bark, among lichens and on the ground. They live in large colonies and are more active during the wet season but retire into the soil during the dry season. Most species reproduce sexually but a few are Parthenogenetic. The eggs are laid in clusters and attached to the tunnel walls. The female exhibits considerable maternal care in both eggs and newly hatched nymphs by remaining near them and driving away enemies.

The nymphs are very similar to the wingless adults. In sexually reproducing species the wing pads of the male nymphs develop internally as imaginal buds until the penultimate molt, appearing as typical wing pads only in the last nymphal instar. This is what exactly happens in holometabolous insects, so that this last nymphal stage may be considered s a pupa.

Order 12 – PLECOPTERA (stoneflies) – the adult stoneflies are moderate-sized to large terrestrial insects with aquatic immature stages. They have two pairs of well-developed wings of similar texture with moderate number of longitudinal veins but a large number of crossveins.

The eggs are laid in masses of several hundreds to several thousands into the water which hatch in a short time. Nymphs of smaller species mature in one year but the larger species require two years to complete their development. The fully grown nymphs crawl out of the water, take a firm hold onto some object preparatory to the final molt. The adult emerges in about a minute or less and after a few more minutes the wings become expanded and hardened for fight.

Order 13 – ZORAPTERA – These are very minute insects with both winged and wingless adult morphs. The head is oval, distinct; the mouthparts mandibulate; antennae, long, nine-segmented; cerci, one-segmented. The wingless forms do not have compound

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eyes and the ocelli, if present are vestigial; the winged morphs have both compound and simple eyes. The two pairs of delicate membranous wings have only one or two veins which may be branched. As in termites, these wings are shed by the adults, and only small stubs are left attached to the body.

The order is one of the rarest among the insects. It contains only one family in which there is only a single genus.

These insects live in rotten wood or under dead bark in colonies of a few to a hundred individuals. They feed mainly on small arthropods, such as mites and small insects. The biology of these insects is not well known.

Order 14– PSOCOPTERA (Psocids, Booklice) – these are very small insects with mandibulate mouthparts, very long antennae, small prothorax and no cerci. The two pairs of wings are similar in texture but the front pair is much larger than the hind pair; venation is simple or reduced. In some species the wings are small, scale-like or wanting. They are inconspicuously colored or have marked protective coloration. They feed on various sorts such as fungus mycelium, lichens, dead plant tissue, and dead insects and even on their species. They live in a wide variety of habitats, including dead or dying vegetation, barks, and fence posts and even in nests of birds and rodents. Several species inhabit moldy things or objects. The adult female lays it eggs singly or in groups on the surface of spots which the frequents. Strands of silken threads are spun by the female over the eggs and attach them to the surface of the support. The eggs hatch in a few days and the nymphs pass through six instars, becoming adults in 3 or 4 weeks time. Several psocid species cause considerable damage to libraries by eating the starchy sizing in the bindings of books and along the edges of pages. Titles of books are defaced necessitating rebinding and repairs. A few species may contaminate food and other marketable goods to such an extent that large quantities must be discarded.

Order15- PHTHIRAPTERA (Chewing and Sucking Lice) – these vary in size from 3mm to 10 mm long; in shape and habits, some being long and slender, others short and wide; some are rapid and active in movement, others sedentary and sluggish. Their mouthparts are of the mandibulate type but greatly reduced. They are host specific or parasitize a group of closely related species. They live entirely on the host body and have continuously and overlapping generations throughout the year. Chewing lice feed on bits of feather, hair, scaly skin, clotted blood and surface debris. The female glue their eggs to the hair or feathers of the host. Many species of chewing lice infest domestic animals and birds causing considerable loss. In domestic birds they cause loss of weight and reduces their laying capacity. They have debilitating effects on domestic animals such as cattle, horses, goats, sheep, dogs and cats. The suckling lice occur normally on mammalian host and feed on blood which is sucked through a tube formed by their eversible stylets. The female glues the eggs to the hair of the host and in a few days hatch into nymphs very similar to the adults. The entire life cycle is spent on the host and breeding occurs through the year. Sucking lice are a menace to man and inflict great losses on livestock.

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The loss to livestock is partly due to irritation and partly to loss of blood resulting in poor condition of the animal and failure to gain weight.

Order 16– THYSANOPTERA (Thrips) – these are small elongate insects, about 3 to 3 mm long, with 6 to 9 segmented antennae, large compound eye and compact lacerating-sucking type mouthparts. In species with well-developed wings, the two pairs are very long and narrow, with one or two veins or none and fringed with fine long hairs along the entire or at least the hind margin. They occur commonly in flowers of various plants causing slight to considerable damage but a large number are predaceous on mites and small insects. The predatory species occur under bark of dead trees and in ground cover.

Order 17 - HEMIPTERA (Bugs and their allies) – this is a group of highly diverse insects characterized by piercing-sucking mouthparts forming a beak, simple metamorphosis, large compound eyes, three to ten-segmented antennae and two pairs of wings with relatively simple or reduced venation. The Hemiptera can be divided into two large group or suborders, the Homoptera and the Heteroptera.

Sub-order Homoptera – members of this group have the membranes of the front wings entirely translucent: the beak arises from the posterior portion of the head; and the head has a typical tentorium. This suborder includes the cicadas, aphids, leafhoppers, scaly insects, whiteflies, mealy bugs and jumping plantlice.

a. The Fulgorid-Cicada Series. Members of this series have the flagellum of the antennae needle-like and the tarsus 3-segmented. The Membracidae, or tree-hoppers have a greatly enlarged pronotum ornamented with ridges, horns or prongs. The Fulgoridae or lantern-flies have bizarre projections of the head and large foliaceous wings. The Cercopidae or spittle bugs are so named because the nymphs produce masses of white froth substance and live hidden beneath it. The Cicadidae or cicadas are large insects measuring about 2 inches or more. They can be recognized structurally from related families by their three distinct ocelli located dorsally on the head; the highly developed musical organs in the males which make a thrill noise during warm days and summer evenings; and by the enlarged front legs of the nymphs.

In most species of cicadas the nymphal period is from 32 to 5 years. Some species however have nymphal life of 13 to 17 years and the periodic nature of their cycle have resulted in the appearance of huge swarms, the ovipositing females causing serious damage twigs and branches of valuable trees.

The Cicadellidae or leafhoppers is the largest family in the order Hemiptera. Most leafhoppers are les than 10 mm long and the long hind tibiae been longitudinal rows of spines. They are mostly slender and parallel-sided, although a few species are broad or angular. The females have strong ovipositors

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for inserting their eggs into plant stem and leaves. Their destructiveness is attributed to their feeding habits and their ability to transmit virus diseases.

b. The Psyllid-Aphid Series. Insects in this series have either short and stout or long and thread-like antennae; wings with greatly reduced venation; and one or two-segmented tarsi.

To Psyllidae or jumping plant lice and the Aleyrodidae or whiteflies have a simple life cycle in which the female and male adults are small, winged and similar in general appearance. The late nymphal stages are flat, inactive or sluggish and scale-like.

The remaining families of the psyllid-aphid series are divided into large groups; the Aphidoidea which includes the aphids and their allies; and the Coccoidea which consist of the mealybug and the scale insects.

The Aphidoidea are characterized by the two-segmented tarsi in most species; the presence of several veins and a stigmal area in the front wings of winged morphs; and a complex life cycle which consist of alternative generations of Parthenogenetic and gamic individuals. The Aphididae or plantlice, is the most important family in the group which includes the largest number of species that transmit plant viruses. Their sucking activity is also of the great economic concern as the sudden upsurge of an aphid population may wipe out a large field of crop in so short a time.

The Coccoidea canbe recognized from the Aphids by their relatively simple life cycle; wingless females that are extremely sluggish or completely fixed in position; and are covered by a tough scale, a waxy secretion or a hard integument; small and delicate males having a single pair of wins with only or two simple veins.

Among the families of cocoidea, the Diaspididae is one of the most important groups. The females are small, sedentary, soft-bodied insects hidden beneath the scale which is a protective covering. They have extremely reduced appendages and the body becomes merely an egg sac at maturity. As the eggs are gradually laid, the body shrinks, so that the egg mass occupies the entire protective covering. The first instar nymphs crawl out of the protective covering and move with rapidity in all directions thus effecting there widespread distribution. The nymphs become sedentary after the first molt and each form of scale. Many species of scale insects are among the most destructive pests of agriculture.

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The mealy bugs or Erioccocidae, are another important group, attacking many plants. They form no scale but secrete waxy filaments which may cover the entire insect or just the periphery.

Suborder Heteroptera – Members of this suborder have the beak typically arising from the posterior portion of the head; the general areas fusing behind the beak to form a gula; they lack a tentorium and the front wings have thickened bases and membranous spices.

The female of this group lay their eggs singly or in groups glued to stems or leaves. In some species the eggs are inserted into plant tissues or into damp substrate. Many species are predatory while still others are plant-feeders. The plant-feeding species are as economically important as the plant-feeding members of the Homoptera.

Series Neoptera – the members of this series are called the neoropteroid orders. All have complete metamorphosis and are therefore frequently also termed the Holometabola.

Order 18 – HYMENOPTERA – (Sawflies, Ants, Bees, and Wasps) - This order includes insects of varied body shapes and sizes ranging from 0.1 mm. to about 50 mm. they characterized by heavily sclerotized integument, mandibulate type of mouthparts, although in many forms the mouthparts are modified for lapping or sucking. The wings are well-developed, reduced or wanting; if well-developed the two pairs are transparent and are of similar texture, without scales but with complex or reduced venation. The antennae range from 3 to about 6-segmented and come in various shapes. The Hymenoptera is one of the largest orders of insects in number of species already known. Many species are beneficial to man.

Order 19 – COLEOPTERA (Beatles and Weevils) – the adult of these insects have the first pair of wings hard, shell-like and veinless. This pair of wings serves for the second pair which is membranous, veined and used for flight. The mouthparts are of the mandibulate type; the antennae well-developed; the compound eyes conspicuous, and the legs heavily sclerotized.

Most species of beetles are plant-feeders but some are predatory on other insects. Both larvae and adult of the same species may be plant feeders or both may be predaceous, although the larvae may not feed on either the same species of plant or the same part of the plant. June beetles, for example, are phytophagous but utilize the different parts of a plant for food during their development. The adult feed on foliage of trees, but the larvae or grubs, feed on the roots of trees, shrubs, herbs and grasses. Certain groups of beetles have more specialized food habits while still others are endoparasites of other insects or feed on insect eggs.

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Most members of the order are terrestrial. Certain groups however, are aquatic, both immature stages and adults living in water. In aquatic species, the larvae usually leave the water to pupate in an earthen cell in a nearby soil.

The eggs are laid late February or early March and hatch in 1 or 2 weeks. The larvae are voracious feeders and when fully grown pupates in the soil. The adult emerged in a few weeks, feeding and maturing during the months June, July and up to early September. The biological pattern may, however deviate from one group to another. For instance, some ladybirds beetles have continuous and overlapping generations throughout the summer months.

Order 20 – MEGALOPTERA (Dobsonflies and Alderflies) - These are large insects having terrestrial adults and pupae but aquatic larvae. The adults have long antennae, mandibulate mouthparts, large eyes and two pairs of wings that are of similar texture and venation.

The female lay their eggs in large clusters on stones or other objects over-hanging the water. The eggs hatch soon after deposition, and the tiny larvae wriggle their way out into the water. The larvae are predaceous on small aquatic animals. When mature, they leave the water and make a pupal cell in damp soil or in a rotten wood nearby. The pupal stage lasts about two weeks.

Order 21 – NEUROPTERA (Lacewings, Mantispids) – these insects are minute to large insects, with two pairs of transparent wings having numerous veins and crossveins; mandibulate mouthparts; long and multisegmental antennae; and large eyes. Most members of the order are terrestrial and predaceous but one family is aquatic. The larvae of aquatic forms live in and feed on fresh-water sponges.

The matispids have a striking resemblance to preying mantids. The front legs of both groups are greatly enlarged and fitted for grasping insect prey. Larvae of Mantispids feed on egg sacs as spiders or the contents of wasps nests. The first instar larvae, however, enter the parasitoid stage ___________________________ a suitable food reservoir. The succeeding larval instars are grub-like having degenerate legs.

The adult “lacewings” have clear and abundantly veined wings. The female lay their eggs by either attaching them directly to foliage or by a long hairlike stalk attached to a leaf. The larvae that hatch from the eggs are active but sluggish, soft-bodied and frequently bearing warts, tubercles and long hair. Their mouthparts are modified for sucking the body juices of their prey. The prey on small insects, insect eggs but frequently attach aphids which have earned for them the common name ”aphidlions”. The fully grown larvae spin a woolly ovoid cocoon on the nether surface of a leaf or in some sheltered place where pupation take place.

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The larval stages of “antlions” live in sandy soil, digging cone-shaped pits that trap ants and other prey which fall into them. The fully grown larvae pupate by forming a cocoon in the soil.

Order 22 – MECOPTERA (Scorpionflies) - the adults of this order have the wings large and net-veined, short or aborted. They have long antennae, large eyes, slender legs and mandibulate mouthparts which are often located at the end of snoutlike elongation of the head.

The ovoid eggs are laid in or on the ground, either singly or in clusters. The larval stages live in densely wooded areas among moss, rotten wood, or rich mud and humus. They feed on various types of organic matter. The fully grown larvae pupate in the soil. The adult are omnivorous, feeding mostly on small insects, and take nectar, pollen, petals, fruits and mosses as supplementary food.

Order 23 – SIPHONAPTERA (Fleas) – these insects are mostly small, about 2 to 4 mm, although a few may attain a length of about 6 to 8 mm. the adults are wingless, have long stout spiny legs; short clubbed antennae which fit into a depression along the side of the antennae in repose; mouthparts fitted for piercing skin and sucking blood of the host; and laterally flattened bodies.

The minute, whitish, oval eggs are dropped by the female on the host or in the nest. They soon hatch into larvae that live in the soil or debris in the nest and feed on the debris or grass. The larvae, when full grown spin an irregular cocoon and pupate in the nest of the host.

Adult fleas are extremely active, slipping through hair and feathers with great facility. Adults of some species stay on the host most of their lifetime while others stay in the nest and get on the host for feeding purpose only. They feed primarily on the blood of mammals but a few species prey on birds and occasionally are pests of domestic fowls.

Order 24 – DIPTERA (Flies) – Adult flies have only the front pair of wings conspicuous and functional and which are membranous or rarely scaled with a few cross veins and a moderate number of longitudinal veins. The hind wings are reduced to knobbed balancing organs called halteres. A few species are completely wingless. Mouthparts are either modified for piercing and sucking or for rasping and lapping.

In most species, the eggs are simple, ovoid or elongate and are normally laid in, on or near the larval food. The larvae of most flies are moisture loving. They live in water, in rotting flesh, inside the bodies of their hosts, in decaying fruit, most organic material or even inside living plant tissue. The food and habitat of the adult flies are usually different from those of the larvae. The adults of many groups feed chiefly on nectar, plant sap or free liquids associated with rotting organic matter. Certain families, such as horse flies and mosquitoes feed on animal blood.

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Order 25 – Trichoptera (Caddisflies) – there are mothlike insects whose larval stages and pupae are aquatic. Their mandibulate mouthparts have most of its components reduced or sub-atrophied. They have long, multisegmented antennae; large compound eyes; long legs, and in most two pairs of large membranous wings except for some wingless or brachypterous females of few species. In most species the body and the wings have hair instead of scales, although in a few members of this new order, the antennae, palpi, legs, and wings may have patches of scales or scattered scales among the longer hairs.

Caddisfly females lay their eggs in various ways. In some species, the female enters the water, discharges the eggs in strings and grouping them into irregular masses on stones or some other objects. In other groups, the female extrude the eggs, from them into a large mass at the tip of the abdomen and encasing them with a gelatinous matrix before depositing them in sticks or stones which are submerged in, or adjacent to, over hanging in water. According to reports these egg masses swell and liquefy, and the eggs hatch during a rain. The active larvae feed mostly on small aquatic animals and microorganisms. In many species the larvae construct portable cases of various types to protect the greater part of their bodies. When full grown, the larvae spin cocoon and pupate. The pupae possess strong mandible with which the mature pupa cuts its way out of the cocoon. The preadult instar swims to the surface, crawls on some object and transforms into adult.

Order 26 – Lepidoptera (Moths, Butterflies, and Skippers) – There are insects whose body, two pairs of wings and other appendages are covered with scales which are often brilliant in color and arranged in beautiful patterns. The adult mouthparts are greatly reduced, the remaining components forming a fused, elongated coiled tube for sucking up liquid food. They have large compound eyes, long, multisegmented antennae, and well-developed legs. The eggs are laid singly or in mass in various patterns on or near the larval host plants. The larvae are cylindrical, most of them having a definite head, thoracic legs, and five pairs of larvapods. The pupae are usually brown and hard and the appendages appear cemented onto the body. The larvae of most Lepidoptera are plant feeders, except for a few species that are predaceous, scavengers or feeders on stored products. A great many of the species feeds externally on the foliage; a large number mine leaves and petioles and another large number bore into stems, trunks, fruits and roots.