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Chapter 5

Evolution and Classification

78 5. Evolution and Classification

This chapter discusses the origin of insectsand their evolutionary history (phylogeny).The basics of taxonomy and classification ofinsects and their allies are briefly introducedand their kinship to other organisms in theanimal kingdom is indicated. The outline ofthe main features of spider-like animals andhexapods comprises their general biology aswell as their economic and ecological signifi-cance. The description of common insectfamilies encountered in Papua New Guineatogether with the illustrations and the colourplates can be used as a field guide for theidentification of insects.

5.1 Phylogeny of Insects

The evolutionary history called phylogenyobtains support mainly from morphology butincreasingly also from biochemistry. Thecomparison of morphological features andmolecules provides valuable information forphylogeny. The most important tool forphylogeny is homology, the structural similar-ity due to common ancestry. The various typesof insect legs, shown in fig. 2-20 are adaptedfor fulfilling different functions like walking,jumping, digging, etc. However, all legs arecomposed of the same parts, coxa, trochanter,femur, tibia, and tarsi, thus showing structuralsimilarity despite the different functions.Another example are the mouthparts ofinsects, discussed in chapter 2.1.2.2, thatallow deduction of common ancestry fromhomology. Further evidence for phylogeny isprovided by palaeontology, the study offossils, described in chapter 5.2.

Insects most probably evolved from a worm-like ancestor, as shown in fig. 5-1. Onecharacteristic of insects and their postulatedancestors is metameric segmentation. Thebody of segmented animals is composed ofrepeated organisational units. These areobvious in Annelida such as the earth wormbut less conspicuous in insects due to thefusion of segments. The insect head forinstance is the result of such fused segments.

During the course of evolution, articulatedlegs developed on each segment. Insects havethree pairs of legs associated with the threethoracic segments. The legs of the other seg-ments either were reduced or serve purposesother than locomotion. Structures like man-dibles, maxillae, antennae and terminalappendages are homologous to legs, adaptedfor different functions but of the same origin.The development of wings is closely associ-ated with the evolutionary success of insects.Wings are unique structures, since insects are

Fig. 5-1: Hypothetical stages in thedevelopment of body regions and appendagesfrom a worm-like ancestor (top) to a primitiveinsect (bottom). P: prostomium, M: mouth(reproduced from Ross, H.H. et al., 1982)

5. Evolution and Classification 79

the only class of Arthropoda, in which theyhave evolved. Apart from insects, there aresome vertebrates which have the ability to fly.Their wings however, are modified penta-dactyl limbs, that are analogous to insectwings. On the way to the modern wingedinsects, there were ancestors with three pairsof wings, one pair on each thoracic segment.The prothoracic wings were lost during evolu-tion so that only two pairs of wings were lefton the meso- and metathorax.

5.2 Fossil History

Palaeontology studies fossils and the evolu-tionary history of organisms, that formedthem. The earliest hexapod fossil, a springtail(Collembola), was dated back to the LowerDevonian Era, 380 million years ago. The firstinsects seem to have been present during theDevonian Period. Quite a diversity of insectshad evolved in the Upper Carboniferous and anumber of now-extinct orders like Meganiso-ptera, Megasecoptera and Palaeodictyo-ptera lived 300 million years ago. Meganiso-pteran insects resembled dragonflies and werethe largest known insects, some with giganticwingspans of up to 75 cm. Fossils revealedthat piercing-sucking mouthparts for feedingon plants had already evolved during the fern-dominated Carboniferous. The diversificationof insects however coincides with the appear-ance of Angiosperms in the Cretaceous, 135to 65 million years ago. From this time, theoldest Lepidoptera and Hymenoptera are

known and the modern insect fauna started todevelop. Excellent specimens are preserved inamber, as shown in fig. 5-2 B. Amberoriginates from hardened resin and insects aresometimes entrapped. Amber is transparent,therefore it is an outstanding preservative.Amber specimens are in a much bettercondition than specimens derived from com-pression fossils. However, an amber specimenwith an enclosed mosquito that had suckedblood from a dinosaur is not suitable forextraction of dinosaur DNA from bloodremains in the mosquito’s gut in order toreconstruct the dino. This story narrated in themovie ‘Jurassic Park’ is, of course, fiction.

5.3 Taxonomy and Classification

The task of taxonomy is to describe, nameand classify insects. Taxonomy is very time-consuming work, to sort out thousands ofspecimens requires considerable skills. Themajor obstacle to insect taxonomy however, isthe large number of insect species. Mostscientists assume that only 5 to 20% of theinsect species, ie. 750,000 species aredescribed so far. The conflicting total numberof species of all organisms ranges between 4.4million and 100 million. Therefore it is sheerspeculation whether there are in total 3 to 5million undiscovered species, or 30 millionunknown arthropods, or almost 100 millionspecies yet to be described, as extrapolatedfrom canopy fogging. Whatever number isright, a common conception is that more than

Fig. 5-2: Fossil insects: (A) Dunbaria fasciipennis from Lower Permian, (B) the oldest known antSphecomyrma freyi from Upper Cretaceous preserved in amber (reproduced from Ross, H.H. et al., 1982)

A B


56% of all species are insects. However, thisfigure might be slightly lower, since recentsurveys of the deep sea floor revealed veryhigh numbers of marine organisms, estimatinga total of 10 million marine species.

Somebody calculated that there are 425 de-scribed species per insect taxonomist. Takingthe above estimates into account, there is atremendous amount of work to be done byinsect taxonomists. In other words, perhaps1000 to 10,000 species are to be described byeach insect taxonomist. It is assumed thatabout 6% of the world’s total number ofspecies can be found on New Guinea island.How many hundreds of thousands or evenmillions of insect species are left to bedescribed only in Papua New Guinea? This isdefinitely a good incentive to train a largenumber of mangi binatang.

Regarding the relative number of species inthe various orders of the animal kingdom,shown in fig. 1-1, some adjustments might benecessary. The beetles are estimated to be byfar the most diverse order of organisms. How-ever, recent studies of the rain forest canopyon Borneo elucidated higher species numbersof Hymenoptera and Diptera.

From all these figures, the dilemma oftaxonomy - the diversity of insects - becomesquite evident. Systematics studies the kinds

and diversity of organisms and their inter-relationships. As in taxonomy, diversityhampers the progress of systematics. Touncover the origin of taxa, the taxonomicunits such as genera or families, systematicsrequires the study of closely related speci-mens. These are often not available becauseonly a tiny fraction of insect species isdescribed so far. As a result of this dilemma,only the major taxa like insect orders arecommonly recognised by all taxonomists.Controversial debates however ignite amongstscientists, when it comes to families and othersubordinate taxa. Moreover, the position ofcertain higher taxa such as Coleoptera andHymenoptera is still unclear, hence will besubject to further revision. In this chapter thesystematics proposed by ‘The Insects ofAustralia’ (CSIRO, 1991) was adopted.The findings of phylogenetic, taxonomic andsystematic studies are compiled in clado-grams, exhibiting the relationships of particu-lar taxa in tree-like diagrams. This is the taskof classification. A cladogram of majoranimal groups illustrating the position of theArthropoda including insects is shown in fig.5-3. The evolutionary relationships of hexa-pod orders are indicated in fig. 5-11. Asshown in box 5-1, each scientific name has aparticular suffix appended indicating therespective taxonomic category (taxon).

TAXON SUFFIX EXAMPLE COMMON NAMEClass Insecta Insects

Subclass Pterygota (winged insects)Infraclass Endopterygota (wings develop internally)

Order Lepidoptera Butterflies and mothsInfraorder HeteroneuraSeries DitrysiaSuborder GlossataSuperfamily -oidea Papilionoidea

Family -idae Papilionidae SwallowtailsSubfamily -inae PapilioninaeSupertribe -itaeTribe -ini TroidiniSubtribe -ina or -iti

Genus Ornithoptera BirdwingsSubgenus

Species O. priamus Priamus BirdwingSubspecies O. priamus poseidonForm O. priamus poseidon f. kirschii

Box 5-1: Taxonomic categories and their standard suffix


5.4 Identification of Specimens

Specimens are usually identified by the use ofidentification keys. These keys lead theinvestigator through a sequence of choicesbetween exclusive character descriptions.Finally, all specimens except the one underobservation are eliminated. Most commonlyused are biforked dichotomous keys offeringtwo options per character description. Theseare either in spider-format as shown in fig. 5-4 or in the more convenient linear format, eg.:

107(106) Cerci with 4 or more segments ................ 108Cerci with 1-3 segments .......................... 110

108(107) Head hypognathous or ophistognathous;pronotum shield-like and rounded in outline,usually covering all or part of head; bodydorsoventrally flattened and oval ...................................(wingless cockroaches) BlattodeaHead proganthous; pronotum not shield-likeand not covering head; body cylindrical andmore elongate .......................................... 109

There are some problems with dichotomouskeys. The key has to be strictly followed fromthe beginning and a choice has to be made foreach character description. Identification isalmost impossible, if a feature of the specimenis missing, for instance because it is brokenoff the specimen. Furthermore, beginners whoare not yet familiar with the specifictaxonomic terminology might face consider-able problems understanding which featurethe key is talking about. It can become a verytime-consuming enterprise, if one has totackle a huge key, as for instance the key tohexapod orders in ‘The Insects of Australia’(CSIRO, 1991). In case the specimen belongsto an order described at the end of this key,one has to find his way through up to 116different character descriptions. However,other key formats and types of keys exist, thatare more user-friendly. Outstanding examplesare computer-supported interactive multi-media keys, like LucID Player - Contem-porary Identification Tools for Biology:

University of Queensland, Department of Entomologyand Cooperative Research Centre for Tropical PestManagement (1997): LucID Player - ContemporaryIdentification Tools for Biology, CD-ROM; Version1.0; Brisbane; Australia

Interactive keys allow identification to startwith any feature of the specimen and usuallylead to the right insect order after three to fouroptions. A large number of supportive figuresas well as explanations enable even beginnersto quickly identify the order of a specimen.Furthermore, the software can be used forcreating personal keys, for instance to theidentification of particular groups of insects.

5.5 Synopsis of the AnimalPhylum Arthropoda

80% of the animal species belong to the groupArthropoda. Arthropoda are characterised by

• segmented body with paired appendages• improved locomotion due to segmentation

of legs (Arthropoda = jointed-legged)• development of chitinous exoskeleton• posterior appendages involved in feeding• ventral nervous system• open circulatory system• gas exchange via spiracles and tracheae.

Arthropoda, Annelida (segmented worms)and a few other smaller taxa form the groupArticulata, shown in fig. 5-3. Arthropods canbe further divided into three subphyla, theTrilobita, Chelicerata and Mandibulata. Theextinct marine Trilobita were the earliestknown members of the Arthropoda, that lived600 to 200 million years ago. Chelicerata andMandibulata are further outlined below, thefeatures of selected groups are summarised inbox 5-2 and fig. 5-4.

Articulata

Arthropoda Annelida

Nemertini Mollusca

Aschel-minthes TentaculataPlathel-minthes Protostomia

Deuterostomia

Echnindermata e.g. Vertebrata,

Fig. 5-3: Evolutionary tree indicating therelationship between Arthropoda and otheranimal groups (graphic Schneider, M.F.)


Class Order Pairs Pairs Mouth- Develop- Pairs of Tagmata Otherof Legs of Wings parts ment Antennae Features

Crustacea crabs, lobsters 5 or more nil chewing with meta- 2 C, A limy exo-crayfish, prawns morphosis skeleton

Arachnida spiders, mites/ 4 nil various gradual nil C, A only simpleticks, scorpions, types eyes; chelice-harvestmen rae, pedipalps

Chilopoda centipedes 9 or more nil chewing gradual 1 H, A poison fangsDiplopoda millipedes two pairs nil chewing gradual body many-

per segment nil 1 H, A segmentedInsecta Isoptera l: 3 chewing gradual 1

a: 3 2 chewing 1 H, T, AOrthoptera l: 3 chewing gradual 1

a: 3 2 chewing 1 H, T, AHemiptera l: 3 piercing-sucking gradual 1

a: 3 2 piercing-sucking H, T, AColeoptera l: 0 or 3 chewing complete

a: 3 2 chewing 1 H, T, ADiptera l: nil D chewing complete

a: 3 1 various types 1 H, T, ALepidoptera l: 0 or 3 chewing complete

a: 3 2 siphoning-tube type 1 H, T, AHymenoptera l: nil D chewing complete

a: 3 2 various types 1 H, T, A

key: C = cephalothorax H = head T = thorax A= abdomen D no true legs l = larva a = adult

Box 5-2: Summary of features of selected arthropod groups

5.5.1 Subphylum Chelicerata

The body of Chelicerata is divided into twomajor regions, cephalothorax and abdomen,also called ophistosoma. The cephalothorax,specialised for feeding and locomotion, bearssix pairs of appendages, four pairs of walkinglegs, one pair of pedipalps and one pair ofchelicerae. The chelicerae are prehensileappendages associated with the mouth andhomologous to antennae. The pedipalps arehomologous to walking legs and are oftenchelicerate. True antennae are lacking. Theabdomen, specialised for reproduction, lacksappendages. Three classes belong to theChelicerata, the Merostomata, Pycnogonidaand Arachnida. The Arachnida or spider-likeanimals are further discussed below.

Class ArachnidaSpider-like animals are mainly terrestrial, onlya few mites are aquatic. The abdomen ofArachnida is typically larger than theircephalothorax. The development is gradualwithout metamorphosis. Many species of this

group, mainly ticks and mites, transmitdiseases or are pests of various crops. There-fore, spider-like animals are included inentomology. The class is further divided intonine to ten orders. A summary of features isgiven in box 5-2, figs. 5-4 and 5-5.

5.5.1.1 Order Araneae (True Spiders)General biology: About 30,000 species oftrue spiders can be found world-wide. Neitherpedipalps nor legs are chelicerate. Theabdomen is constricted to form a thread-wasted joint with the cephalothorax. Thepedipalps of males are involved in the transferof sperm and are of diagnostic importance.The sperm is placed on a spun net, filled intothe pedipalps and transferred to the femalegenital organs. Males are usually smaller thanfemales and are sometimes eaten by thefemales when approaching or after copulation.The females usually guard the eggs and youngspiders (brood care and parental care). Theeggs of many species are placed in a cocoon,that is attached to the mother’s body andcarried around.


Another characteristic of true spiders is thethree to four pairs of abdominal spinnerets.These produce a complex, elastic but strongthread, sometimes consisting of manysupportive individual threads and sticky liquidcoatings or droplets. The thread is used tobuild nets and cocoons. Young spiders mainlydisperse along a thread, spun into wind. Theform and shape of nets is utterly diverse andspecies-specific, thus used for diagnosticpurposes. Nets can be wheel-like, funnel-like,triangular-shaped, ladder-like, bower-like orwork like pitfall traps. The nets are almostinvisible, therefore small animals might gettrapped and become entangled in the systemof threads. The movement of the prey alertsthe spider, that immediately comes to kill it.For this purpose spiders possess poison glandsin their chelicerae. The venom is injected intoprey in order to immobilise or kill it or is usedfor defence. Large hairy hunting spiders cancause painful bites, but it is doubtful whetherthe poison is fatal for a healthy adult human.The exclusively predacious spiders live oninsects and other smaller animals. Spidersdeveloped a wide range of strategies to gethold of prey. It is a common misconceptionthat most spiders use nets to snare prey. A

large number of species hunt prey by means ofjumping at it or running it down. Evenambush is common as in crab spiders that hidein flowers and wait for insects searching fornectar. Most spiders are terrestrial, but someconquered aquatic habitats and hunt on thesurface of water. However, prey is notnecessarily killed instantly, in some cases thetrapped prey is tied up and wrapped in web forconsumption at a later time. Prominent horri-fying species are the bird-eating spiders (fig.5-6 B) of Papua New Guinea, and tarantulasand black widows which originate fromtropical and subtropical America. Other exam-ples occurring in Papua New Guinea likeNephila maculata, are shown in fig. 5-6.Economic and ecological importance:Spiders are truly beneficial animals, since theyare very important for the regulation of insectpopulations.

5.5.1.2 Order Acari (Acarina: Mites, Ticks)‘Dancing on the head of a pin’ is definitelyimpossible for most animals. However, a largenumber of mites, the smallest Arachnidacould do it. The size of these creatures rangesfrom a fraction of a millimetre, invisible to thenaked eye, to about one centimetre in ticks.

external mouthparts,winged

(Insecta)

mouthparts lieinside the head(Entognatha)

three pairs of legs(Hexapoda)

two pairs of legsper body segment

(Progoneata)

one pair of legsper body segment

(Chilopoda)

nine or morepairs of legs(Myriapoda)

one pair of antennae(Antennata)

two pairs of antennae(Crustacea)

with antennae(Mandibulata)

abdomen attachedby narrow stem

(Araneae)

legs often very long,body stout and oval

(Opiliones)

abdomen not soattached(Acari)

abdomen unsegmentedor if so, with spinnerets

pedipalps pincer-like, body flattened

(Pseudoscorpiones)

first pair of legsvery long

(Pedipalpi)

tail-like tip of ab-domen with stinger

(Scorpiones)

abdomen segmented,no spinneret

without antennae(Arachnida)

Arthropoda

Fig. 5-4: Key for the identification of selected groups of Arthropoda (graphic Schneider, M.F.)


Fig. 5-5: Arachnida orders: (A) Scorpiones (B) Pedipalpi: Amblypygi, (C) whiptail scorpions(Pedipalpi: Uropygi), (D) Palpigradi, (E) Pseudoscorpiones, (F) spiders (Araneae), (G) harvestmen or daddy longlegs (Opiliones), (H) Solifugae, (I) Ricinulei, (J) mites and ticks (Acari)(reproduced from Remane, A. et al., 1981)

General biology: Mites have one or morepairs of simple eyes laterally on the frontalpart of the body. The body typically is withoutsegmentation and seems to consist of only onetagma. The segments bearing chelicerae andpedipalpi are fused to form the minute so-called capitulum or gnathosoma, separated

from rest of the body, the idiosoma. Themouthparts are of piercing-sucking type,suitable for sucking up plant juices or theblood of animals. Mites either breathe throughspiracles located near the mouthparts ordirectly through the cuticle. The last pair oflegs is often reduced. During the development

Fig. 5-6: Araneae: (A) Nephila maculata, (B) bird-eating spider Selencosmis crassipes, (C)jumping spider (photos Schneider, M.F.)

A B C

D E F

G H I

J

A B C


of mites and ticks, one larval instar with threepairs of legs only is followed by threenymphal instars, the proto-, deuto- and trito-nnymph, with four pairs of legs, shown in fig.5-7. The nymphal instars resemble adults.Between the instars, prior to moults, theanimals often undergo a resting stage. Underideal conditions, it takes about one to threeweeks for most species to complete their lifecycle. Most Acari species are oviparous, butovoviviparity and viviparity are also notuncommon.

Fig. 5-7: Stages of the life cycle of thetropical red spider mite Tetranychus cinnaba-rinus (Tetranychidae) (reproduced from Hill, D.S.and Waller, J.M., 1988)

Ecological importance: Despite the generalreduction of a number of evolutionary ad-vanced Arachnida features, mites show anenormous adaptability to various habitats andsources of food. Mites are either herbivores,predators or ectoparasites (see fig. 4-10 B).Most species are terrestrial, but there is also anumber of aquatic species. Due to their smallsize, mites are often neglected in biodiversityinventories. However, research has revealed astunning diversity and abundance of thisanimal group in the tropical rain forest. Mitedensities can sometimes exceed 10,000individuals per m². Most of the species arebeneficial predators or harmless phytophages

and fungivores, feeding on fungi or micro-organisms that grow on plant surfaces. Aclose mutualistic interaction between pre-dacious mites and a large number of differentplants has evolved. Numerous predaciousmites per leaf keep plants free of plant-parasitic mites. In return, plants provideshelter for mites during their moult, for layingeggs and protect the animals from sun, rainand larger predators. Leaf hairs, pouches andpits in vein axles and similar structures on theupper- and underside of leaves are calleddomatia, if they offer ideal hiding places formites. The more domatia a plant has to offer,the more predacious mites will eventuallydwell on the plant, hence the more effectivelythe plant will be protected by its ’body guards’.

Economic importance: A large range ofmites and ticks are severe pests of crops andstored products or ectoparasites of man,livestock and pets. Furthermore, many speciesare potential carriers of diseases.Itch mites or scabies mites like Sarcoptesscabiei belong to the family Sarcoptidae. Theanimals are minute and of hemispherical bodyshape with four pairs of very short legs. Theylive in the epidermis of humans and othermammals, causing itchy inflamed patches ofthe infested skin, referred to as scabies ormange. Mites of the family Psoroptidae,shown in fig. 5-8 A, are also minute with ovalbodies and legs exceeding the body margin.These ectoparasites are restricted to particularbody regions such as ears, neck, feet and tail,where the mites settle at the base of the host’shairs and cause itchy irritations of the skin.Dogs with sore tips of the ears usually sufferfrom this kind of mite. The itchy sensationresults in the dog scratching off the skin of itsears. A common pest of man is Demodex fol-liculorum. The minute blood-sucking chiggermites (Trombiculidae) are common intropical and subtropical areas and can causedermatitis. Furthermore, they are knownvectors of scrub typhus. The domestic housedust mites like Glycyphagus domesticus andDermatophagoides pteronyssinus can causesevere allergic reactions in humans. Hard-bodied ticks (Ixodidae), shown in fig. 5- 8 B,


Fig. 5-8: Acari: (A†) sheep scab mite (Psoropt-idae), (B†) fowl tick (Argasidae), (C††) citrus rustmite Phyllocoptruta oleivora (Eriophyidae),(D†††) blister mite Eriophyes sp. (Eriophyidae)(reproduced from Pyenson, L.L., 1980²†; Hill, D.S. &Waller, J.M., 1988††; Ross, H.H. et al., 1982†††)

are small to medium-sized blood-suckingparasites of humans and many other animals.Characteristic for this kind of tick is theirrounded, leathery body. Male ticks arecompletely covered, females partially, by adorsal, shield-like scutum. The ticks remainattached to their host for several days untilthey fall off. The soft-bodied ticks (Argas-idae) lack a scutum. The cuticle of theseblood-sucking parasites is roughened andwrinkled. Some Ixodidae and Argasidae tickstransmit very severe diseases like meningitis.Pests of stored products like flour, grain, driedfruits, cheese and meat belong to the familyAcaridae (= Thyroglyphidae), like the flourmite Acarus siro (= Tyroglyphus farinae).These mites can cause dermatitis in peoplefrequently handling infested products.A large number of plant-parasitic mitesconsiderably reduce yield of crops and might

eventually kill their host plant. Particularly inagricultural systems, spider mites becamesevere secondary pests. Due to their stylet-likemouthparts, the mites are able to pierce andsuck juices from individual plant cells. Thus,mites can avoid most of the defencemechanisms of the plant. In addition, shortgeneration times of one to three weeks pairedwith a high reproductive potential easily allowthe animals to over-exploit their hosts. Pestsof crops are spider mites, red spiders ortwospotted mites (Tetranychidae), shown infigs. 5-7, 8-7 A and gall, rust and blister mites(Eriophyidae). Some species of the latterfamily, shown in fig. 5-8 C and D, cause anabnormal development of the epidermal plantcells forming galls or other deformations ofthe leaf surface. The latter kind of damage isreferred to as erineum and can be confusedwith fungous growth. The piercing-suckingaction of mites can also result in grey orbrown mottling of the foliage.Important agents for biological control belongto the predacious families Phytoseiidae andStigmaeidae. Mites like Typhlodromus andPhytoseiulus are reared commercially in largequantities. After their release in an infestedarea, these predators effectively suppressplant-parasitic mites and other small insectpests. See also chapter 8.7.2 and fig. 8-7 A.

5.5.1.3 Order Opiliones (Opilionida)The harvestmen or daddy longlegs compriseabout 3000 species world-wide. They arecharacterised by a stout, oval or round bodyshape, and legs that are usually up to five ormore times as long as the body, as shown infig. 5-5 G. Many species are predacious,running after their prey on trees or groundcover. Some species are minute, with shortlegs.

5.5.1.4 Order Scorpiones (Scorpionida)The true scorpions are a small group shown infig. 5-5 A. Scorpiones dwell in warmertropical and subtropical areas. Characteristicare the pincer-like (chelate), prehensile pedi-palps and a venomous stinger at the highlyagile tail-like tip of the abdomen.

A B

C

D


5.5.1.5 Order PseudoscorpionesPseudoscorpions are an abundant order ofsmall animals, hardly exceeding 8 mm inlength. Like Scorpions, the Pseudoscorpionspossess chelate, prehensile pedipalps, but lackthe slender tail-like tip of the abdomen includ-ing the stinger, as shown in fig. 5-5 E.

5.5.1.6 Order PedipalpiPedipalpi are tropical and subtropical small tomedium-sized nocturnal animals. The order isfurther divided into Amblypygi and Uropygi(whiptail scorpions), that are shown in fig. 5-5B and C.

5.5.2 Subphylum Mandibulata

The subphyllum is divided into the Crustaceaand Antennata, indicated in fig. 5-4. Thecharacteristics of Mandibulata groups aresummarised in box 5-2. Typical features are:

• head separated from thorax• head with one or two pairs of antennae• three or four pairs of feeding appendages or

mouthparts

Class CrustaceaCharacteristic for Crustacea or Diantennataare two pairs of antennae, one pair ofmandibles, two pairs of maxillae and fivepairs of legs. The body is composed of head,thorax and abdomen, but head and thorax areoften fused to form the so-called cephalo-thorax. During their development, the animalsundergo metamorphosis. Most groups areaquatic, either marine or in freshwater. How-ever, some are amphibious like crayfish orexclusively terrestrial like the sowbugs andpillbugs (Isopoda). The class is divided intoseveral subclasses comprising eg. lobsters,crabs, prawns, shrimps, crayfish and isopods,shown in fig. 5-9 A to D.

AntennataThe Antennata (or Tracheata) bear only onepair of antennae and possess tracheae, thatevolved independently from the trachealsystem of spider-like animals. Antennata arecomposed of four classes, the Chilopoda,Progoneata, Insecta and Entognatha.

Fig. 5-9: Mandibulata: (A-D) Crustacea: (A)Amphipoda; (B) Isopoda; (C) shrimp; (D) cray-fish; (E) Chilopoda (centipedes); (F) Diplopoda(millipedes) (reproduced from Ross, H.H. et al., 1882)

Superclass MyriapodaChilopoda together with Progoneata are bysome authors referred to as Myriapoda.

5.5.2.1 Class Chilopoda (Centipedes)The Chilopoda or centipedes (fig. 5-9 E)possess one pair of legs per segment and havea characteristic curved poison claw on the firsttrunk segment. The animals are mainly noc-turnal predators, hiding under logs, stones orin soil during the day. Some tropical specieslike the huge Scolopendra gain a body lengthof 20 to 25 cm and can cause painful bites.

5.5.2.2 Class Progoneata (Millipedes)The class Progoneata consists mainly ofDiplopoda, called millipedes or thousand-

A B

C

D E

F


legged worms, shown in fig. 5-9 F. Theseanimals have two pairs of legs attached toalmost every trunk segment, resulting in fiftyor more pairs of legs. Millipedes differ fromthe predacious centipedes in feeding mainlyon decomposing plant materials such as leaflitter. Therefore, millipedes play an importantrole in decompositional habitats. Upon distur-bance, the animals curl up and exude a brownfluid containing irritating tannins. The tan-nins are metabolites derived from ingestedleaf litter and are used for defence.

Superclass HexapodaThe superclass Hexapoda - the animals withsix legs - comprises the classes Insecta andEntognatha. Characteristic for Hexapoda is

• their segmented body• three pairs of legs, each pair attached to

one of the three thoracic segments• one pair of antennae• in winged forms one to two pairs of wings

The relationship between hexapod orders isshown in the cladogram in fig. 5-11. Thefeatures of some selected orders are sum-marised in box 5-2 and fig. 5-4.

5.5.2.3 Class EntognathaThis class includes the orders Collembola,Diplura and Protura. Formerly the threeorders were included in the subclass Aptery-gota (wingless insects). However, in contrastto insects, the primarily wingless Entognathatypically have modified chewing ento-gnathous mouthparts, which lie inside thehead in a cavity formed by oral folds of thegenae. The animals are ametabolous and lacka metamorphosis. During their developmentEntogantha undergo multiple moults of ten ormore in number and continue to moult evenafter sexual maturity. Most species of thethree orders are small and unpigmented soil-dwellers (fig. 4-17), that play an importantrole in nutrient recycling.

Order Diplura [two tails]The order Diplura comprises the mostprimitive Entognatha, shown in figs. 4-17 and5-10 A. The animals typically lack eyes.

Order Protura [one tail]Animals of the order Protura are also withouteyes. Their antennae are greatly reduced andthe forelegs are antennae-like (fig. 5-10 B).The first few abdominal segments might bearreduced legs. Some species are predacious,feeding on other soil-dwelling arthropods, asshown in fig. 4-17.

Order Collembola (Springtails) [sticky tail]Collembolans, also called springtails, greatlydiffer from diplurans and proturans. Charac-teristic is the forked spring-like furcula that isused by the animal for saltatorial locomotion.The furcula is made of the fused vestigial legsof the fourth abdominal segment. Inspringtails, the number of abdominal seg-ments is reduced to six. Most species are soil-dwellers, some can be found under bark or areassociated with mosses. A few species areaquatic, living on the surface of water. Somespecies dwell on glaciers. See also figs. 4-17and 5-10 C.

Fig. 5-10: Entognatha: (A) Diplura, (B)Protura, (C) Collembola (springtails) (repro-duced from CSIRO, 1991)

A

B

C


Fig. 5-11: Cladogram of hexapod orders (reproduced from Gullan, P.J. and Cranston, P.S., 1994)

5.5.2.4 Class InsectaThis class comprises hexapods with externalectognathous mouthparts, ie. mouthparts thatare not enclosed in the head. The class isdivided into two subclasses, the primarilywingless Apterygota and the winged Ptery-gota. The pterygote orders can be furtherdivided into two infraclasses, the Palaeo-ptera, the ancient-winged insects that cannotfold their wings and the Neoptera, the moreadvanced insects with foldable wings. Thewings of Endopterygota develop internally,whereas wings of Exopterygota developexternally (see fig. 5-11 and chapters 2.2.9and 5.6.2). Endopterygota are holometa-bolous with complete metamorphosis andpossess a pupal stage. All Apterygota areametabolous, their adults develop graduallyfrom the immature forms through multiplemoults. Insects of all other orders undergo

hemimetabolous development with incom-plete metamorphosis in Palaeoptera andgradual metamorphosis in Exopterygota. Thebody of an insect is typically divided intothree tagmata, head, thorax and abdomen.Each of the three thoracic segments bears onepair of legs. In Pterygota the second and thirdthoracic segments bear one pair of wings each.The abdomen, usually consisting of 11segments, doesn’t bear legs but the eighth,ninth and tenth segment have appendagesmodified for reproductive purposes. Insectspossess an exoskeleton typical for arthropods.The major internal organs are (1) a tubulardigestive tract, (2) an open blood systemdriven by a tube-like heart, (3) a trachealsystem for gas exchange, (4) paired repro-ductive organs opening at the posterior end ofthe body, (5) an intricate muscular system, (6)


Malpighian tubules for excretion and (7) anervous system composed of brain, pairedsegmental ganglia and connectives.The class comprises 29 orders that are furtheroutlined in chapter 5.6. The features of someorders are summarised in box 5-2 and somedistinguishing features between insects andother arthropod groups are shown in fig. 5-4.

5.6 The Insect Orders

5.6.1 Simple Key to Insect Orders

If the insect that you want to identify is• winged, go to ................... key 1 on page 90• wingless, go to ................. key 2 on page 91• aquatic, go to .................... key 3 on page 91

Key 1: Winged Insects

antennae generally clubbed ..................................................... Butterflies, p. 144

scaly wingsantennae not clubbed ..................................................................... Moths, p. 138

narrow without veins, fringedwith long hair, up to 43 mm long .................................................. Thrips, p. 109

hairy wingswings obviously hairy, hind wings muchlarger than forewings, up to 40 mm long ........................... Caddies Flies, p. 132

forewings hard and horny covering all or almost all of hindwings when folded .................... Beetles, p. 112

forewings partly hard and horny-mouth formed into piercing-sucking proboscis ................................. Bugs, p. 106

four wings forceps on end of abdomen ........................................................... Earwigs, p. 98

developed for

forewings leathery jumping ......... Crickets, Grasshoppers, p. 98

long thin for walking .............. Stick Insects, p. 100

no forceps, foreleg thickened forhind legs catching prey ............. Praying Mantids, p. 97

not long .................................................... Cockroaches, p. 95

large head .............................. Dragonflies, Damselflies, p. 94

hindwings wider than forewings,hindwings three-segmented tarsi ............. Stoneflies, p. 94similarin length to head small ---- base of hindwing folded like fan, Alderflies,forewings five-segmented tarsi........... Dobsonflies, p. 110

wings membranous no fan-like areas ................ Lacewings, p. 111

mouth formed into a beak .................... Scorpion Flies, p. 123

two or three long tails ...................................... Mayflies, p. 93

hindwingssmaller than fore- and hindwings no waist present Sawflies, p. 149forewings joined together in flight --

by minute hook waist present ......... Bees, Wasps,Ants, p. 149

front wings reduced to small clubbed halters ... Stylops, p. 122

only two wings hindwings reduced to clubbed halters ......... True Flies, p. 124


Key 2: Wingless Insects

legs adapted for jumping body flattened at sides ................................................................................... Fleas, p. 123

body long, waist has one or two knobs .......................... Wingless Ants, p. 149

with waist waist without knobs .................................. Wingless Wasps, p. 149

length less than 10 mm, tips oftarsi with less than four segments ......................... Booklice, p. 101

legs not adapted for jumping body long length 7-18 mm, tarsi 4 segmented ..........Wingless Termites, p. 96

5-segmented tarsi .............. Stick Insects and their Nymphs, p. 100Wingless Cockroaches and their Nymphs, p. 95

Praying Mantids and their Nymphs, p. 97

body flattened - body long, pointed and scaly with bristles ............. Silverfish, p. 93

body covered with dense hair or scales, no tail ............................ Wingless Moths, p. 138

head not prominent, antennae not visible,resembles a spider ....... Louse Fly or Sheep Ked (Diptera) , p. 130

body flattened head prominent, antennae visible or in groovesfrom above in head, found only on mammals and birds ................. Lice, p. 102

antennae long .............................................. Wingless Bugs, p. 106

not more than five pairs offalse legs, large compound eyes ................ Caterpillars of Moths and Butterflies, p. 134

false legs on abdomensingle small eye on each side of head .......... Sawfly Larvae, p. 147

6-10 pairsfalse legs

small compound eyes with few facets .Scorpion Fly Larvae, p. 123

Key 3: Aquatic Insectstrue legs absent ............................................................................................. Larvae of True Flies, p. 124

legs not well developed: present or absent, jaws present and head prominent ....... Beetle Larvae, p. 112

false legs at end of abdomen

wingless and aquatic no tail often enclosed in case ................... Caddis Fly Larvae, p. 132

facial mask present ........................ Dragon Fly Nymphs, p. 94

head with jaws, short antennae,legs and gills similar and extendedlength of body ........... Alderfly and Dobsonfly Larvae, p. 110

legs well developed two tails or less always two tails, long antennae, no mask

or conspicuous jaws ........................... Stonefly Nymphs, p. 94

tails flattened or leaf-like,facial mask present ........................ Damsel Fly Nymphs, p. 94

three tailstails thin, leaf-like gills at side of abdomenno facial mask ...................................... Mayfly Nymphs, p. 93

hindwings covered by horny forewings which meet in a straight line down middle, mouth parts with jaws ........... Water Beetles, p. 112

adults with wings foundon surface or underwater hindwings cross each other, piercing-sucking mouthparts .. Water Bugs, p. 106

wingless and piercing-sucking mouthparts ............ Water Bug Nymphs, p. 106


5.6.2 Synopsis of Insect OrdersClass: Insecta

Subclass: Apterygota (wingless) pageOrder: Archaeognatha (ancient jaws): Bristletails ......................................................... 92Order: Thysanura (fringed tails): Silverfish, Firebrats ................................................... 93

Subclass: Pterygota (primarily winged)Infraclass: Palaeoptera (old wings): wings cannot be folded

Order: Ephemeroptera (one day, temporary, short-lived wings): Mayflies ................... 93Order: Odonata (toothed mandibles): Damselflies and Dragonflies ............................... 94

Infraclass: Neoptera (new wings): wings can be foldedOrder: Plecoptera (folded wings): Stoneflies .................................................................. 94Order: Blattodea (insect that shuns light): Cockroaches ................................................. 95Order: Isoptera: (equal wings): Termites ........................................................................ 96Order: Mantodea (prophet): Praying Mantids ................................................................ 97

not occurring in PNG Order: Grylloblattodea (cricket that shuns light): Ice Crawlers ..................................... 97Order: Dermaptera (skin-like wings): Earwigs .............................................................. 98Order: Orthoptera (straight wings): Locusts, Grasshoppers, Katydids and Crickets ..... 98Order: Phasmatodea (phantom, ghost or spectre): Stick and Leaf Insects ................... 100Order: Embioptera (lively wings): Web- or Footspinners ............................................ 101Order: Psocoptera (biting wings): Booklice, Barklice, Psocids .................................... 101

not occurring in PNG Order: Zoraptera (purely wingless)............................................................................... 102Order: Phthiraptera (wingless lice): Lice .................................................................... 102Order: Hemiptera (half wings): Bugs, Lerps, Aphids, Scales, Cicadas, etc. ................. 103Order: Thysanoptera (fringed wings): Thrips .............................................................. 109

Endopterygote Orders (wings develop internally; with pupal stage)Order: Megaloptera (large wings): Alderflies and Dobsonflies ................................... 110

not occurring in PNG Order: Raphidioptera (fused wings): Snake-Flies, Camelneck-Flies ........................... 110Order: Neuroptera (nerve- or net-like wings): Lacewings and Antlions ...................... 111Order: Lentilburgeroptera ........................................................................................... 112Order: Coleoptera (sheath-wings): Beetles ................................................................... 112Order: Strepsiptera (twisted wings): Stylops ................................................................ 122Order: Mecoptera (long wings): Scorpion Flies, Hanging Flies ................................... 123Order: Siphonaptera (tube-wings): Fleas ..................................................................... 123Order: Diptera (two wings): True Flies, Midges, Mosquitoes, Crane Flies, etc. .......... 124Order: Trichoptera (hairy wings): Caddis Flies ........................................................... 132Order: Lepidoptera (scale wings): Butterflies and Moths ............................................ 133Order: Hymenoptera (membranous wings): Sawflies, Wasps, Bees and Ants ............. 147

The following outline of insect orders is based on suggestions given by CSIRO

5.6.3 Outline of Insect Orders

5.6.3.1 Archaeognatha (Bristletails)[ancient jaws]General biology: Fusiform subcylindrical,primitive wingless insects with the ability tojump when disturbed. The body is with orwithout hypodermal pigmentation, bearingpigmented scales. The compound eyes arelarge, ocelli are present. The filiform antennaeare long and multisegmented, the mouthpartsectognathous. The thorax is strongly archedand has stout legs. The females lay singleeggs in cracks and little cavities with their

well developed slender ovipositor. The ab-domen has ten complete abdominal segments,the eleventh forms the long caudal filamentand bears two shorter filiform cerci (fig. 5-12A). Segments two to nine bear pairs ofvestigial legs called stylets. Ametabolousdevelopment with multiple moults, even aftermaturity. The immature stages resembleadults. Families: Meinertellidae, Machilidae.Economic and ecological importance: Bristle-tails are associated with decompositionalhabitats and can be found under stones andamongst leaves where they mainly feed onhumus. They are of no economic importance.


5.6.3.2 Thysanura (Silverfish, Firebrats)[fringed tails]General biology: Cursorial, more or lessflattened, primitive wingless insects. Thebody is scaled or bare, with or withoutpigments. The compound eyes are reduced orabsent, ocelli are almost always absent. Theantennae are long, multisegmented andfiliform. The chewing mouthparts are ecto-gnathous. The thorax is not strongly arched.The abdominal segments 7 to 9 bear styliformvestigial legs. Females lay eggs in cracks andother secluded places with their well developedslender ovipositor. The caudal filament andcerci are long and filiform, generally subequalin length (fig. 5-12 B), but might be short insome species. The cerci are strongly divergingfrom the body axis. Ametabolous develop-ment with large and indefinite number ofmoults, even during adult stage. The youngdevelop very slowly. Some families are theLepismatidae and Nicoletiidae.Economic and ecological importance: Thesilverfish are extremely fast runners. Asdomestic cosmopolitans, silverfish such as thecommon Lepisma saccharina (loves sugar!)are pests of households consuming virtuallyeverything containing starch like books orclothing. Some species are reported to trans-mit diseases. Silverfish like cool damp placeswhereas firebrats prefer warmer places. Somespecies are slender subterranean soil-dwellers,others live in ant nests.

Fig. 5-12: (A) Allomachillis sp. (Archaeogna-tha, Bristletails), (B) Acrotelsella sp. (Thysan-ura; Silverfish) (reproduced from CSIRO, 1991)

5.6.3.3 Ephemeroptera (Mayflies)[one day, temporary, short-lived wings]General biology: Long slender, small tolarge, soft-bodied palaeopteran insects withshort and bristle-like antennae. The aquaticnymphs (naiads) have well developed chew-ing mouthparts, adults lack functional mouth-parts. The triangular wings are net-veined andcan’t be folded. The second pair of wings issmaller than first pair, or lacking in somespecies. The abdomen of the nymphs andadults has two to three appendages, two longfiliform cerci and one or no terminal filament(fig. 5-13). The naiads have tracheal gills onthe abdomen. The adults live only for half anhour or up to several days. Incomplete meta-morphosis with naiads similar in generalstructures to adults. The metamorphosis ofmayflies is unique among insects. They arethe only known example of an immature stagehaving functional wings. This stage is calledsubimago. Some families are the Caenidae,Leptophlebiidae and Baetidae.Economic and ecological importance: Thenaiads can be found under rocks and logs increeks and ponds. They feed on algae andplant matter. Ephemeroptera are important forthe trophic structure in aquatic environmentssince the naiads are a crucial source of foodfor freshwater fish.

Fig. 5-13: Ephemeroptera (Mayflies): (A)aquatic nymph Centroptilum sp. (Baetidae),(B) adult ♂ Atalophlebia sp. (Leptophlebiidae)(reproduced from CSIRO, 1991)

A B

A

B


Fig. 5-14: Odonata (Damselflies, Dragonflies):(A) aquatic damselfly nymph Caliagrion sp.(Zygoptera: Coenagrionidae), (B) copulatingdamselfly adults in tandem position, Coen-agrion sp. ♂ above, ♀ below (Zygoptera: Coen-agrionidae) (reproduced from CSIRO, 1991)

5.6.3.4 Odonata (Damselflies, Dragonflies)[toothed insects]General biology: Predacious palaeopteranmandibulate insects. The medium-sized tolarge nymphs and adults possess chewingmouthparts. The adults have very short hair-like antennae, large compound eyes, two equalor subequal pairs of long elongatemembranous many-veined wings with a con-spicuous, dark coloured field on the proximatefront part of the wings (pterostigma). Thenaiads are aquatic and have an elongate,prehensile labium for seizing prey. Thenymphs of the Zygoptera (fig. 5-14 A) havethree leaf-like terminal tracheal gills on theabdomen, whereas larval Anisoptera ‘breathe’through internal ridge-like rectal gills. Hemi-metabolous development with incompletemetamorphosis. The eggs are laid below thesurface of water on objects like rotten logs orin ribbons or rings in the water. Odonata havevery long generation times. The 17 familiesare divided into three suborders, the Zygoptera(damselflies) like Coenagrionidae, Mega-podagrionidae and Lestidae, the Anisoptera(dragonflies) such as Libelluidae, Gomph-idae, Corduliidae and Aeshnidae, and theAnisozygoptera, the latter not occurring inPNG. Damselflies are of slender and delicateappearance with a fluttering flight and a verypeculiarly shaped thorax. During rest the

wings are aligned almost parallel to theabdomen The colourful and stout bodieddragonflies with their strong and gracefulflight hold their wings during rest extended tothe sides. Adult Odonata are well known fortheir mating behaviour which is unique ininsects. During mating the male grasps thefemale’s neck by the help of terminal claspers.The female then bends her abdomen forward(tandem position), as shown in fig. 5-14 B.Economic and ecological importance:Damsel- and dragonflies are utterly beneficialand important for maintaining the trophicbalance in aquatic ecosystems. Both adult andimmature stages are predacious. Adults catchprey such as mosquitoes, horse flies andmidges on the wing with their legs. The naiadsdwell on the bottom of rivers, ponds and lakesand live on other aquatic insects andcrustaceans.

5.6.3.5 Plecoptera (Stoneflies)[folded wings]General biology: Medium-sized to large,somewhat flattened mandibulate exopterygoteNeoptera. The forewings are slightly longerthan the lobed hindwings. Both adults (fig. 5-15 A) and aquatic nymphs (fig. 5-15 B) havechewing mouthparts, well developedcompound eyes, usually three, rarely twoocelli and multisegmented, long and slightlytapered antennae. Adults have two subequalpairs of long membranous multiveined wings.The tip of the abdomen bears one pair of shortor long multisegmented cerci. The immaturestages are mostly aquatic with gills on thethorax or on the first two or three abdominalsegments. The naiads are either predacious,herbivorous or omnivorous, feeding on algae,other plant material. They can be easilylocated and collected from overturned stonesin rivers and creeks. Gradual metamorphosiswith up to thirty moults. The order is dividedinto two suborders, the Arctoperlaria likeNotonemouridae and the Antarctoperlariaincluding the families Austroperlidae, Gri-popterygidae and Eustheniidae.Economic and ecological importance: Stone-flies are like mayflies and Odonata important

A B


for maintaining the trophic balance in aquaticecosystems, and are thus beneficial insects.They provide a valuable source of food forfreshwater fish. Furthermore Plecoptera arevery sensitive to pollution and are thereforeused as indicator organisms.

Fig. 5-15: Plecoptera (Stoneflies): (A) aquaticlarva Stenoperla sp. (Eustheniidae), (B) adultIlliseoperla sp. (Gripopterygidae) (reproducedfrom CSIRO, 1991)

5.6.3.6 Blattodea (Cockroaches)[insect that shuns light]General biology: Fast running, medium-sizedexopterygote Neoptera with dorsoventrallyflattened body. Nymphs and adults havechewing, hypognathous mouthpart, that aredirected downwards in repose. The head ofmost species is completely covered with alarge pronotum. The filiform antennae areusually bent backwards and are often longerthan the body. The compound eyes are welldeveloped. The forewings, when present, areusually modified into hardened tegmina forthe protection of the hindwings. The hind-wings, if present, are membranous andbroadened at the rear by the formation of ananal fan, which is an important diagnosticfeature. The wings of many species or inparticular sexes are reduced to wing pads. Thelegs are usually long and adapted for running(cursorial), in some species for digging(fossorial). The tarsi are 5-segmented. Theabdomen is many-segmented and bears onepair of cerci. The eggs are enclosed in anootheca, containing 15 to 40 eggs. Theootheca is glued or otherwise deposited on

substrate or externally carried by females.Ovoviviparous and viviparous species keepeggs internally in ‘uterus’ or brood sac, untilthe eggs hatch. Parthenogenesis is commonin some species. Gradual metamorphosis,shown in fig. 2-36, with slowly growing andvery active nymphs. Adults and nymphs areoften aggregated, living together in families.The Pacific wood roach Cryptocercus punctu-latus lives in colonies and develops an almosttruly social life. Cockroaches are a veryancient order of winged insects with fossilrecords dating back 400,000,000 years. Thelifespan of cockroaches can be up to four orfive years, however only a few individualslive their full lifespan. Cockroaches possessscent glands that release a very unpleasantodour for defence purposes. Most species arenocturnal and adapted to dark and humidhabitats, and various climatic and altitudinalzones. The order is very diverse in the Tropics,where some species can become really hugelike the giant tropical cockroach Megaloblattablaberoides or the Madagascar giant hissingcockroach Gromphadorina potentosa. Theorder is divided into five families, the Poly-phagidae, Blaberidae, Nocticolidae, Bla-tellidae, Blattidae and Cryptocercidae. Thelatter family is not occurring in PNG.

Fig. 5-16: Blattodea (Cockroaches): (A†)Blatta germanica (Blattidae), (B††) Periplanetaamericanus (Blattidae) (reproduced from Ross,H.H., 1982†; CSIRO, 1991††)

Economic and ecological importance: Mostspecies are harmless omnivorous forestdwellers. However, two species of undesiredbut common cockroaches, shown in fig. 5-16and box 5-3, are cosmopolitans dwelling

A B

A B


Feature German Cockroach American Cockroach(Blatta germanica) (Periplaneta americanus)

Appearance light brown with dark streaks down the back reddish brownSize small, 5 - 15 mm large, 35 - 45 mmNumber of offspring/year 400,000 800Feeding habits look for food in small area, eg. kitchen, movement free-ranging, travelling

usually travel no more than one metre from room to room in search for foodPreferred locations generally found in large groups in warm found in bathrooms, laundries, around

and moist locations like cooking areas pipes or near sewer drains

Box 5-3: Features of common cockroaches associated with human habitations

houses of man. Both species were accidentallydispersed all over the world and can be alsofound in PNG. These pests search for foodduring the night, leaving behind faeces and atypical unpleasant odour. However,cockroaches are not known to transmit anydiseases. Interestingly, the common names ofthese two species vary in French, English andGerman, according to the former political‘enemies’. The common name of Blattagermanica in English is ‘German Cockroach’,the animal is called ‘Prussian’ in French and‘Russian’ in German.

5.6.3.7 Isoptera (Termites)[equal wings]General biology: Termites are eusocialinsects living in colonies and are organised inthree distinct castes, the reproductives(queen, king, winged alates, de-alates andneotenics), the wingless soldiers (intercastes)and the wingless workers. Due to the castesystem, termites vary tremendously in theirmorphology (polymorphism). The biology oftermites is outlined in chapter 3.2.1. Bothnymphs and adults have moniliform antennaeand chewing mouthparts. The jaws of mandi-bulate soldiers of particular species aregreatly enlarged. The cuticle of soldiers andworkers is not sclerotized, but soft and notpigmented. Therefore they are bound to moistand dark environments and have to avoidsunlight (‘sunburn’ and desiccation). Theelongate and membranous wings are held flatover the body at rest. The alates are capable ofshedding their wings after the mating flight bymeans of basal sutures. The abdomen of amature queen is markedly enlarged andadapted for laying 1000 or more eggs per day.

The cerci of termites are short. The gradualmetamorphosis is shown in fig. 3-9. Mosttermite species are found in tropical countries.Only two termite species occur in southernEurope but there are 246 species in Australia.Families of termites occurring in PNG areMastotermitidae, Kalotermitidae, Termitidae(Nasutitermes, Microcerotermes, Amitermes,Pericapritermes), Rhinotermitidae (Copto-termes, Rhinotermes, Schedorhinotermes) andTermopsidae. Their soldiers, shown in fig. 5-17, are used for identification. The term‘white ants’ for termites is rather misleadingsince the only feature ants and termites havein common is the fact that both are insects.Therefore this term should be avoided.

Fig. 5-17: Soldiers of Isoptera (Termites):(A) Coptotermes elisae (Rhinotermitidae), (B)Schedorhinotermes spp. (Rhinotermitidae),(C) Nasutitermes novarumhebridarium (Termit-idae), (D) Pericapritermes spp. (Termitidae),(E) Microcerotermes biroi (Termitidae), (F)Mastotermes spp. (Mastotermitidae) (reproducedfrom CSIRO, 1991)

A B

C

D E F


Economic and ecological importance: Mostspecies are beneficial and play an importantecological role as decomposers of decayingwood. However some species can causeconsiderable economic loss as insect pests ofhouseholds, forest plantations and forestproducts as further outlined in chapter 6.2.1.Predators of termites are echidnas, somebirds like parrots and kingfishers and meatants of the genus Iridomyrmex. However,none of these predators can effectively controlthe large number of individuals.

5.6.3.8 Mantodea (Praying Mantids)[prophet]General biology: Medium-sized to large,predacious, diurnal and nocturnal insects withfreely mobile head of characteristic triangularshape. The head bears chewing mouthparts,huge compound eyes and multisegmented,usually shorter, filiform antennae. The pro-thorax is prolonged, the forelegs are raptorialwith sharp hooks and a series of spines forgrasping and holding prey. The forelegs areraised in repose in a ‘praying’ attitude andpossess large mobile coxae. The mid andhindlegs are cursorial. The tarsi are almostalways 5-segmented. The forewings are modi-fied into hardened tegmina, the hindwing aremembranous. The wings of some species orsexes, particularly females are reduced oreven absent, as shown in fig. 2-44 A. Thecerci are short and multisegmented. The eggsare enclosed in an ootheca as shown in fig. 5-18 A. Gradual metamorphosis. The ordercomprises eight families, however only threecan be found in PNG, the Hymenopodidae,the Mantidae and the Amorphoscelidae.Common species occurring in PNG areOrthodera ministralis (fig. 5-18 B) andArchimantis latistylus (fig. 2-44 A), bothMantidae. Praying mantids have developed anumber of defence strategies like crypsis andcamouflage, ie. the resemblance of leaves ortwigs (fig. 4-8); scare tactics, ie. the wingsare often very colourful and are opened whendisturbed; and chemical defence, ie. theanimals regurgitate deterrent digestive fluidsfrom their mouth. The story, that female

praying mantids are cannibals eating theirmales after copulation has to be considered asnot true and probably such observations aredue to captive conditions.Economic and ecological importance: Aspredacious insects mantids play an importantrole in the natural control of insects. Attemptsto use these animals as biocontrol agents,however fail due to the fact that prayingmantids are non-specific predators consumingother beneficial insects as well as pest species.

Fig. 5-18: Mantodea (Praying Mantids):(A) Archimantis spp. ootheca (Mantidae),(B) adult Orthodera ministralis ♀ (Mantidae)(reproduced from CSIRO, 1991)

5.6.3.9 Grylloblattodea (Ice Crawlers)[cricket that shuns light]General Biology: Apterous mandibulateexopterygote Neoptera. The prognathous headbears large, heavily sclerotized mandibles andfiliform, multisegmented antennae. The smallanimals lack ocelli. The legs are cursorialwith large coxae, wings are not present. Thecerci are long, flexible and segmented. Theovipositor in females is strongly projecting.The nymphs are subterranean soil dwellers.See fig. 5-19 A.Economic and ecological importance: Thegrylloblattids are bound to temperate climatesand there are no recorded species of this orderin the southern hemisphere. World-wide thereare 21 described species.

A B

Fig. 5-19: (A) Grylloblatta spp. (Gryllo-blattodea, Ice Crawlers), (B) Chelisoches spp.(Dermaptera: Chelisochidae, Earwigs) (repro-duced from CSIRO, 1991)

5.6.3.10 Dermaptera (Earwigs)[skin-like wings]General biology: Medium-sized, elongate,heavily sclerotized, and thus brown to blackexopterygote Neoptera. The head is pro-gnathous, bearing chewing mouthparts at itsapical tip. The compound eyes are large,ocelli are lacking. The antennae are long,slender and multisegmented. The adults arewinged or wingless. The forewings, whenpresent, are reduced to small tegmina. Thehindwings are membranous and semicircular,are almost entirely made up of an anal fan andare completely hidden by the tegmina at rest.The relatively short, cursorial legs have 3-segmented tarsi. The cerci are modified intoconspicuous unsegmented terminal forceps,shown in fig. 5-19 B. The nymphs of somespecies possess long, multiarticulate cerciinstead of forceps. Gradual metamorphosiswith up to six moults. Some species areviviparous. The females often guard the eggsand nymphs, until the young can care forthemselves. World-wide there are ten familiesin three suborders, however most speciesoccur in the Tropics. Seven orders can befound in PNG: Anisolabididae, Labiduridae,Apachyidae, Spongiphoridae, Forficulidae,Chelisochidae, Pygidicranidae.

Economic and ecological importance: Mostearwigs are nocturnal omnivores. The animalslive hidden under bark, logs, stones, in soiland cavities of any sort during the day. Somespecies are predacious. Earwigs are of littleeconomic importance, although a few phyto-phagous species are reported to cause damageto ornamental plants and agricultural crops.

5.6.3.11 Orthoptera (Crickets, Katydids,Grasshoppers and Locusts)[straight wings]General biology: Medium-sized to large,elongate mandibulate exopterygote Neoptera.The hypognathous head has chewing mouth-parts and large mandibles both in nymphs andadults. Orthoptera have medium to largecompound eyes and usually three, ocelli, thatcan be absent or reduced in number in somespecies. The antennae are short or severaltimes as long as the body with the number ofsegments varying from 7 to many. The saddle-like pronotum has large descending laterallobes. The hindlegs are elongate with enlargedfemora, usually saltatorial, the fore- andmidlegs are gressorial. The forelegs of somespecies have spines for grasping or arefossorial. The tarsi are 1- to 4-segmented,terminal claws are mostly present. The wingsare usually well developed but can be reducedor absent. The forewings are formed intonarrow and hardened tegmen that cover thehindwings and overlap across the median. Thehindwings are membranous and many-veined,folded fan-like in rest and are very colourfulin some species. The cerci are unsegmentedand short. The females possess an ovipositor.Many species have stridulatory files forsound production and tympanal organs forhearing, eg. on tibiae of the forelegs, furtheroutlined in chapters 2.2.6 and 3.1.1. Thenymphs usually undergo five larval instarswith gradual metamorphosis. Twisted wingbuds (fig. 5-20 G) can be found in maturenymphs. The order comprises some of thelargest insects with a body length of morethan 11 cm and wingspans of more than 22cm. The world’s largest katydid Siliquoferagrandis (Tettigoniidae: Phyllophorinae) can

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be found in PNG. The order Orthoptera isrelatively diverse with more than 20,000described species. World-wide there are 28families. 14 families can be found in PNGbelonging to the two suborders Ensifera andCaelifera.

Suborder Ensifera: nocturnal insects havinglong antennae with more than 30 segments,crickets excepted. Some families are:• Gryllidae Crickets are chirping insectssimilar to Tettigoniidae, but with fewer than30 antennal segments. The head is concealedunder the large pronotum. The forewings areheld flat and are broader at their base. Thetarsi are 3-segmented, the ovipositor slenderand needle-like, the are long cerci. Commonin PNG is Teleogryllus spp. (fig. 5-20 A).• Gryllotalpidae Mole crickets have largeand broad fossorial forelegs that are used as ashovel. The antennae are much shorter, buthave more than 30 segments. Common inPNG is Gryllotalpa spp. shown in fig. 5-20 B.• Tettigoniidae Katydids, bush crickets orlong-horned grasshoppers are vegetarianswith very long antennae and 4-segmentedtarsi. The females have a short, sickle-like orlong sword-like ovipositor. The wings aresometimes short or absent. The tympanalorgan is located at the inner side of the tibiaeof the forelegs, shown in fig. 2-29. Commonin PNG are Siliquofera grandis, Phasmodes(fig. 5-20 C), Phaneroptera, Holochlora andCaedicia (fig. 5-20 D, Plate 3 B).

Suborder Caelifera: with shorter antennae(fewer than 30 segments). Some families are:• Pyrgomorphidae are characterised bytheir conical heads as in the case of Atracto-morpha similis (fig. 5-20 E), Desmoptera andPsednura.• Acrididae Plague locusts and grasshoppershave a tympanum on each side of the firstabdominal segment near the base of thehindwings. The ovipositor is short. Valangairregularis, one of the world’s largest short-horn grasshoppers, occurs in Australia andPNG. Common in PNG are Chortoicetesterminifera (fig. 5-20 G), Acrida, Sphingnotus,Locusta migratoria (fig. 3-8) Gastrimargusand Nomadacris guttulosa (fig. 5-20 F).

Fig. 5-20: Orthoptera (Crickets, MoleCrickets, Grasshoppers): (A) Teleogryllus spp.♂ (Gryllidae), (B) Gryllotalpa spp. ♀ (Gryllo-talpidae), (C) Phasmodes ranatriformis ♀ (Tetti-goniidae), (D) Caedica major ♀ (Tettigoni-idae), (E) Atractomorpha similis ♀ (Pyrgo-morphidae), (F) Nomadacris gullulosa ♂ (Acrid-idae), (G) Chortoicetes terminifera last larvalinstar ♀ (Acrididae) (reprod. from CSIRO, 1991)

Some locusts exhibit the phenomenon ofphase polymorphism, discussed in chapter3.2. Two morphologically distinct phases canbe found, the solitary phase of singly living,non-migrating individuals and the gregariousphase of migrating and swarm-forming indi-viduals. The different appearance of the two

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phases, shown in fig. 3-8, made scientistsbelieve for a long time, that they belonged todifferent species.Economic and ecological importance:Migrating grasshoppers also called plaguelocusts, are mainly recruited from the super-family Acridoidea. The mostly phytophagousinsects can cause considerable damage toagricultural crops and pastures in the tropicsduring outbreaks (calamities). Adult as wellas larval plague locusts are able to formswarms of innumerable individuals as de-scribed in the Old Testament:“... I will bring locusts into your country tomorrow.They will cover the face of the ground so that it cannotbe seen. They will devour what little you have left afterthe hail including every tree that is growing in yourfields. They will fill your houses ...” Exodus 10:4-6

During sustained flights, locusts can travelseveral hundreds of kilometres. During anoutbreak of the Desert Locust Schistocercagregaria in West Africa in the late 80’s, ahuge swarm succeeded in crossing the Atlanticocean. This incredible exercise becomes evenmore stunning, if one realises that the distancebetween the American and African continentis about 5,000 km and that there is no islandin between for repose. During outbreaks, alarge number of people, deprived of theircrops, depend on locusts as a source of food.Apart from damage caused to agriculturalsystems, grasshoppers are also pests offorestry. The insects are able to ringbark andeventually kill young seedlings and saplingsin nurseries or newly established plantations.

5.6.3.12 Phasmatodea (Stick and Leaf Insects)[phantom, ghost or spectre]General biology: Medium-sized to largemandibulate, phytophagous, exopterygoteNeoptera. The stick- or leaf-like, mainlyelongate and slender insects have a round,prognathous head with chewing mouthparts.The antennae are short to very long andslender, having 8 to more than 100 segments.The head bears three or sometimes fewerocelli. All three pairs of legs are gressorial,long and slender, sometimes thorny. Wingsare present or absent mostly in females. The

tegmen are nearly always short, covering onlya small part of the hindwings and overlappingeach other in repose. The remigium of thehindwings is tough, the large anal areas aremembranous. Females are often much largerthan the males. The males are absent in somespecies like Carausius morosus and thefemales reproduce parthenogenetically. Theeggs are free with a tough, thick shell and aconspicuous cap-like lid (operculum), shownin fig. 5-21 A. The eggs are laid singly anddropped into leaf litter. Gradual meta-morphosis with prolonged egg development.The order is divided into three families, twoare present in PNG, the tropical Phyllidae(leaf insects), eg. Phyllium spp. (fig. 5-21 Band Plate 1 D) and Phasmatidae (stickinsects or walking sticks). One of the world’slongest stick insects, Hermachus morosus,can be found in PNG. Other common speciesin PNG are the bizarre ghost insects Extato-soma papoi horridus and Eurycantha horridashown in figs. 5-21 D and 4-13 A andPhasma gigas. Phasmatodea are very wellcamouflaged and hard to detect in theirnatural habitat, as shown in fig. 4-11 B. Stickinsects move very slowly and feign death,when disturbed.

Fig. 5-21: Phasmatodea (Stick and LeafInsects): (A) Extatosoma sp. egg, (B) Phylliumsp. ♀ (Phyllidae), (B) Sipyloidea sp. ♀, (C) Ex-tatosoma spp. ♀ (Phasmatidae) (reproduced fromCSIRO, 1991)

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