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Chapter 3

Communication and Sociality

36 3. Communication and Sociality

Receptors and senses have been outlined inchapter 2.2.6. Their outstanding performanceis one of the keys to the success of insects.Receptors are essential devices of a receiverand can be compared with a satellite dish orantenna. A TV set doesn’t work without thesedevices, similarly an insect requires receptorsto respond. Communication and behaviourdepend on information acquired by receptors.The simplest type of behaviour might be areflex. This is a simple reaction as a result ofa particular stimulus, for instance the sponta-neous withdrawal of the hand from a source ofheat. There are two types of movementstriggered by a simple stimulus. An unorientedaction varying with the intensity of thestimulus is called kinesis. We talk abouttaxis, if the movement is towards (positivetaxis) or away from the stimulus (negativetaxis). According to the quality of the stimuluschemo- (related to taste and scent), geo- (re-lated to gravity), hygro- (related to humidity),photo- (related to light), thermo- (related totemperature), phono- (related to sound) -taxisor -kinesis can be defined. Using these terms,a positive phototaxis is a movement towardslight, for instance a plant growing towardslight or a nocturnal insect, like a moth, beingattracted to a light source (see also chapter7.5). When an insect follows a gradient, forinstance the concentration of a pheromone asshown in fig. 3-5, it is called klinotaxis.Insect behaviour generally is innate anddetermined genetically, but simple learninghas been observed in some bees and butter-flies.

Different types of communication are dis-cussed in this chapter. Communicationenables cooperation, without communicationno cooperation. One can easily figure out thechaos as a result of a lack of communicationand cooperation for example in a termitecolony of several million individuals, equi-valent to the population of PNG. Complexbehaviour based on communication includesterritorial behaviour, courtship, brood careand parental care. The latter is important forthe understanding of how sociality in insectsevolved.

This chapter also looks at insect societies,following the evolution from simple aggrega-tions to social insects culminating in theeusocial termites and Hymenoptera like bees,some wasps and all ants.

3.1 Communication

One might tend to believe that insects do nothave much to say, as stated by Piau, J. andLynch, J. in “Communication and Language -Reader” (UPNG; Waigani; PNG; 1989):“Insects have a very limited number of messages thatthey can say or receive. The male of a certain species ofgrasshopper, for example, has a choice of six messages,which might be translated as follows:

• • I am happy, life is good• • I would like to make love• • You are trespassing on my territory• • She’s mine• • Let’s make love• Oh how nice to have made love”

Communication between insects is mainlyabout reproduction, food and territory anddefinitely not about rugby and politics. Sincewe are far away from having a holisticconception of the complex communicationprocesses, especially of social insects, we donot exactly know whether or not there aremore messages that insects exchange.

Communication is defined as informationbeing sent by one individual (sender) andperceived by one or several other individuals(receiver):

sender receiverinformation

The information can be transmitted eitherbetween individuals of the same species(intraspecific) or between individuals ofdifferent species (interspecific). The mediumfor signal transduction in insects is either ofauditory, visual, tactile or chemical nature.

3.1.1 Auditory Communication

In tropical countries sound-producing insectscan be recognised almost all day and night.Amongst those producing sound, cicadas,crickets and grasshoppers are definitely the

3. Communication and Sociality 37

most conspicuous ones. Cicadas are theanimals producing the loudest sounds in termsof sound pressure, although a barking orhowling dog might seem louder to us humans.This is because the main frequency range of acicada is above 20,000 Hz, beyond thedetectable frequency range of human beings.Sonograms display the frequency of soundwaves as a function of time. The sonogramsof some insect sounds are shown in fig. 3-1.

Fig. 3-1: Sonograms of insect sounds: (A)Assassin bug Canthesancus sp., (B) Drummercicada Thopa sp., (C) Black Field cricketTeleogryllus sp., (D) Bush cricket Tettigoniasp., (E) Mole cricket Gryllotalpa sp., (F)Death’s Head moth Acherontia sp. (reproducedby permission of CSIRO Australia from CSIRO, 1996²)

There are several ways of producing sounds:

Air forced through or over small openingscauses a hissing sound. This can be experi-enced, when the Rhinoceros beetle Xylotrupesgideon is touched.

Stridulation or frictional rubbing is the resultof two parts of the body being scrapedtogether. The chirp of a grasshopper or cricketis produced by scraping the front part of thehind wing over the thickened veins of theforewings. Other grasshoppers possess file-like structures on the forewings as shown infig. 3-2, that are rubbed over the inner side ofthe hind femur. Particular assassin bugs(Reduviidae) rub the tip of their proboscisalong a file on the ventral part of theirabdomen (see fig. 3-3).

Fig. 3-2: Stridulatory file under tegmen of aTettigoniidae grasshopper which is rubbedover the hind femur (reproduced from CSIRO, 1991)

Fig. 3-3: Stridulatory file on ventral part ofthorax of a Reduviidae bug. The tip of theproboscis is scraped along the file to producesound (reproduced from CSIRO, 1991)

A

B

C

D

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F


A vibrating membrane called a musicalapparatus is used by cicadas for theproduction of sound. One out of a set ofseveral membranes in ventral pouches at thebase of the abdomen (see fig. 3-4) isconnected with a muscle, that pulls themembrane inwards. Upon relaxation of themuscle, the membrane snaps back, causingvibrations that are amplified by othermembranes. This process is repeated severalthousand times per second.

Fig. 3-4: Musical apparatus of a cicada(Cicadidae). Tymbal cover and operculumremoved at bottom (reproduced from CSIRO, 1991)

Beating substrate with parts of the insectbody is done for instance by some termitesoldiers hitting wood with the tips of theirmandibles or by some grasshoppers usingtheir hind tibiae as drum sticks, hitting theground.

The production of sounds serves variouspurposes. Some insects mark their territory bymeans of sound and for many, sound is themedium of communication for courtship andreproduction. The hissing sound of a Rhinoc-eros beetle upon disturbance is definitely adefence strategy. Other examples for audibledefence are particular Tiger moths (Arcti-idae). These animals are able to produce anddetect ultra sound. Bats use ultrasound fortheir echolocation system in order to detectobstacles and prey during the night. Tigermoths thus are able to recognise anapproaching bat. A number of disastrous Tigermoths use ultrasound to tell the bat: “I amdistasteful, unpalatable to you, leave me inpeace”. Other Tiger moths make a lot ofultrasonic noise and in this way disturb thebat’s echolocation system. As a result of thisinterference, the bat loses orientation andcannot get the moths.

3.1.2 Visual Communication

Visual communication seems to be welldeveloped in insects for various purposes.Bright coloration (warning or aposematiccoloration) of wings and other body parts, asis the case in many moths and butterflies(Lepidoptera) and in bees and wasps(Hymenoptera), plays an important role fordefence as visual mimicry (see chapter4.4.5). Colours also stimulate sexual behav-iour. Some insects have the ability to displayglowing light in darkness, a phenomenon,called bioluminescence. This is an energyrequiring reaction triggered by the enzymeluciferase. Common examples are beetles likefireflies and their larvae, the glow-worms(Lampyridae), click beetles (Elateridae),some springtails (Collembola), the lanternbug (Fulgoroidae) and a few species of trueflies (Diptera). Bioluminescence is used forcourtship signalling and prey-luring.

3.1.3 Chemical Communication

The most important means of communicationin insects is the use of chemical signalsinvolving the senses of smell and taste. No


other group of animals has developed such avariety of hundreds of chemical substances forthe communication between all stages of thelife cycle and sexes. These communicationchemicals or semiochemicals are produced byexocrine glands and released into the envi-ronment. Generally they can be classified aspheromones and allelochemicals.The volatile pheromones are used forcommunication within individuals of the samespecies as trace indicators for instance byants, as courtship pheromones and sexattractants eg. by moths, as aggregationpheromones, spacing pheromones, alarmindicators and for the control of castes insocial insects. The location of a female,emitting a sex attractant is shown in fig. 3-5.Sex attractants can be used for the biologicalcontrol of certain insect pests. A trap can bebaited with the pheromone in order to lure andkill the males, but more commonly anartificial sources of pheromone is placed inthe pest-infested area. The artificial phero-mone superimposes the pheromone trails offemales, thus confusing the males and makingit impossible for them to locate the females.Like most of the semiochemicals, pheromonesact specifically on one particular species. Thatis the reason why there is only a very limitednumber of quite expensive pheromonesavailable for biocontrol purposes.

Allelochemicals facilitate communicationbetween individuals of different species.These substances can be further grouped intokairomones, allomones and synomones.Kairomones benefit the receiver but dis-advantage the producer. An example is thehost-plant detection by a phytophagous insect.Termites or bark beetles are attracted to thescent released by a damaged, thus weakenedhost-tree. Allomones benefit the producer, buthave no effect on the receiver as is the casewith defensive chemicals. Synomones areadvantageous for the producer and thereceiver. Using the damaged host-tree of theabove example, a parasitoid of the bark beetlebenefits from the allelochemical. The paras-itoid is attracted to the damaged tree and findsits host, the bark beetles. As the bark beetlegets killed by the parasitoid, the tree benefitsas well because there are fewer bark beetles,attacking it.

3.1.4 Tactile Communication

Tactile communication uses touch as itsmedium. Ants for instance drum the abdomenof particular plant lice (Aphididae) with theirantennae. This signal makes an aphid release asweet excretion from its anus, that is readilytaken by the ant.

Fig. 3-5: Male moth locating a female releasing a sex attractant. The male follows a gradient ofincreasing concentration of the pheromone (reproduced from Gullan, P.J. and Cranston, P.S., 1994)


3.2 Insect Societies

The degree of social organisation of insectsshows an almost gradual increase in complex-ity from solitary or singly living individualsof particular species, through subsocialaggregations of individuals of a species topresocial (communal, quasisocial and semi-social) species, culminating in highly organ-ised eusocial species, the truly social insects.

SubsocialityThe vast majority of insects are solitary,living singly without exhibiting social behav-iour. The next step towards sociality are non-reproductive aggregations of insects. Form-ing aggregations increases the chances ofsurvival. Commonly encountered are roostingaggregations as shown in fig. 3-6. During thebeginning of 1998, hundreds of this particularnoctuid moth could be observed gatheringaround security lights and making a nuisanceof themselves.

Fig. 3-6: Roosting aggregation of the Noctu-idae moth Nagia episcopalis (photo Schneider,M.F.)

Another interesting example is the migratinglocust or plague locust. These animals areusually solitary. Periodically, when climaticand other conditions are suitable, the locustpopulation booms. The insects then aggregateduring the course of several generations andsuccessively become gregarious. The nymphscan form ‘hopper bands’ of the size of severalhectares, with densities illustrated in fig. 3-7.Adults aggregate into huge swarms that can

Fig. 3-7: Aggregation of the African locustLocusta migratoria, gregarious phase insouth-western Madagascar during a plague in1993. The grasshoppers enjoy the warmthradiated by the bricks (photo Holtmann, M.)

fly long distances without break. Nothing canstop grasshoppers from eating almostanything that is green. Thus, plague locustscan cause considerable damage to pasture andfood crops. The change in behaviour fromsolitary to gregarious is closely associatedwith morphological and physiologicalchanges, a phenomenon called phase poly-morphism. The changes can be so drastic thatscientists considered the two phases asdifferent species. Some morphological differ-ences between solitary and gregarious Locustamigratoria are shown in fig. 3-8. The slightlysmaller gregarious insects have a saddle-likedepression on the pronotum and smaller hindfemora in relation to the body and wings.Intermediate morphologies occur in transientstages, the stages during the transformationfrom solitary to gregarious and vice versa.Phase polymorphism is mainly determined by


the population density and to a certain extentby the presence of a pheromone. Highdensities of locusts have a positive feed-backon the gregarious phase via tactile stimuli.Locusta migratoria, mainly a pest in Africa,can also be found in the Markham Valley,causing severe damage to pasture and cropslike corn and rice. Other species of plaguelocusts are the Desert locust Schistocercagregaria, occurring between northern Africaand Pakistan and Nomadacris guttulosa inAustralia and New Guinea.

Fig. 3-8: Morphological differences betweensolitary (A) and gregarious (B) phases ofLocusta migratoria. See text for more details(reproduced from Gullan, P.J. and Cranston, P.S., 1994)

Social InsectsThe highest behavioural complexity can befound in truly social (eusocial) insects, thatshow the outstanding feature of socialorganisation. Of course, cooperation andcommunication are basic prerequisites forsocial behaviour. Social organisation in thiscontext means that the individuals livetogether as a colony, sharing the same nest.Social animals are restricted to the insect classwith one single exception, the naked molerat Heterocephalus glaber of the mammalorder Rodentia (Bathyergidae). Social in-sects belong to only two insect orders andinclude all species of termites (Isoptera) andcertain species of Hymenoptera, ie. all antspecies and some bee and wasp species. Eu-social behaviour is defined as:

• cooperation of individuals in the care ofthe young (parental care)

• specialisation of distinct groups in a colony(caste system)

• overlap of at least two generations in thelife cycle of the individuals

According to this definition, plague locustsand humans for instance are not eusocialanimals.

Eusocial insects exhibit structurally andfunctionally specialised groups of individuals.This specialisation is referred to as castesystem of reproductives, workers and/orsoldiers with each caste having its specifictasks to fulfil. Which caste a particularindividual will belong to is controlled by oneor more of the following factors: pheromones,the type of food, the age of an individual,haplodiploidy and other mechanisms not yetwell elucidated. The colony size might varyfrom 30,000 to 50,000 individuals in bees toup to one or even 22 million individuals intermite and ant colonies.

3.2.1 Termites

The fascinating but complex biology oftermites is in many regards still a mystery tothe numerous scientists dedicated to termiteresearch. As decomposers remineralising deadplant material, the animals play an outstandingrole in the food chain. However, a largenumber of termite species are of economicimportance as pests in agriculture, forestry,architecture and building. Effective controlmeasures against termites are not reallyavailable due to a fragmentary understandingof termite biology.The simplified model of a termite life cycle,shown in fig. 3-9, indicates the three castes,the reproductives, the soldiers and theworkers. Due to the fact that termites arehemimetabolous insects, even the nymphstake part in the social life and have theirspecific tasks to fulfil. The so far poorlyunderstood concept of caste determinationdoes not seem to be definitive or too rigid.Once the caste of an individual is determined,development into other castes is still possible.Soldiers, also referred to as intercastes might

A

B


turn into workers or even into reproductives,if there is a shortage of individuals of othercastes. This process is controlled by phero-mones. In the case of the queen, there is aspecific ‘queen’ pheromone, preventing otherindividuals from turning into queens. Only ifthe queen is removed or dies, does the lack ofthe specific pheromone promote the develop-ment of a new queen. The morphologicaldifferences of individuals of different castesare shown in fig. 3-10.

Fig. 3-9: Termite life cycle (reproduced withpermission from Hadlington, P., 1992)

Reproductives possess compound eyes andare more or less brown due to their sclerotizedcuticle. Developing reproductives have wingbuds, wings or wing stumps. Reproductivescan be further divided into:• Alates, the young winged reproductives of

both sexes. From time to time about 100 to1000 alates leave the colony for a matingand colonising flight. After mating a pairsettles down at a suitable site like a rotting

scar on a tree in order to establish a newcolony.

• De-alates, alates that cast their wings afterthe colonising flight and successively turninto queens and kings. Initially only a feweggs are laid and brought up by a femalede-alate. As the number of individuals inthe colony grows, the more workers areavailable to help the young queen to carefor the brood. After three to five years thenumber of individuals is already so large,that the colony of a pest species can turninto the damaging stage.

• Queen and king, which are the mainreproductive individuals in a colony. Oncethere are many workers to help the queen,her only job is to produce a tremendousnumber of offspring. A large queen maylay more than 1000 eggs per day. The lifespan of a queen can be as much as 50years.

• • Neotenics assist the queen in laying eggs,once her productivity decreases. When thequeen has died or deteriorated, one of theneotenics takes her place. That is thereason why the removal of a queen fromher colony does not necessarily mean theend of the colony.

Workers are sterile, wingless and blind malesand females. Their cuticle is unpigmented andnot hardened, therefore the animals areconfined to a dark and moist environment.Workers build the nest and galleries, theyfetch food, care for the brood and feedreproductives and soldiers. The worker’s lifespan is one to two years.

Soldiers are, like workers sterile, winglessand blind males and females with anunpigmented, unsclerotized cuticle. Soldiersdefend their colony from intruders by the useof powerful jaws and/or by ejecting a whitesticky repellent from an opening on their head.Soldiers can’t feed themselves, they have tobe fed by workers. Usually the number ofsoldiers is much smaller than the number ofworkers. Soldiers can be mandibulate ornasute, shown in fig. 5-17, depending on thespecies. Therefore soldiers can be used


Fig. 3-10: Castes and different stages of thedevelopment of termites (A) mature queen, (B)winged reproductive (alate), (C) de-alate, (D,E) developing reproductives, (F) mandibulatesoldier, (G) worker (reproduced with permissionfrom Hadlington, P., 1992)

for the identification oftermite species. The lifespan of the soldiers is oneto two years.As decomposers termitesfeed on living or decayingwood. A major compoundof wood is cellulose, acarbohydrate like starch.Breaking down celluloserequires an enzyme calledcellulase. Some termite

Fig. 3-11: Mound nest ofNasutitermes spp. showingthe internal structure (repro-duced with permission fromHadlington, P., 1992)

species have the ability to produce thisenzyme, others live in mutualistic symbiosiswith certain intestinal bacteria or protozoa,that provide the required cellulase. In order tocover their protein requirements, termitesfeed on fungi, growing on decaying wood.The importance of fungi for termites can beseen from the fact that a young queen on hercolonising flight carries a bit of the fungicake in her mouth. Once she settles down tofound a new colony, she inoculates chewedwood with the fungus.Most termite species are harmless to timberand timber products, but others are even sohungry that they chew the plastic insulationof subterranean power and telephone cables.

Termitarium (Nest)The queen, the brood and most of thecolony’s individuals live in a so-calledtermitarium (plural: termitaria). It is com-posed of mud that is sometimes as hard asconcrete and a paper-like substance madefrom chewed wood, as shown in fig. 3-11.The conditions inside the nest are dark, moistand cool and suit the requirements of themostly blind unpigmented termites with theirsoft cuticles. Runways or galleries are builtby the workers radially from the nest in alldirections and connect the termitarium with

E F G

C DB

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Fig. 3-12: Mound nest of Amitermes meridi-onalis; north/south view of the mound (repro-duced with permission from Hadlington, P., 1992)

sites where the colony gathers food. Thesegalleries are either subterranean about 20 to50 cm deep or are built from mud (mudpacks or mud galleries), attached to a stemor other substrates. The termites’ road systemcan be enormous and reach a radius of 50 to100 metres around the nest.

Fig. 3-13: Subterranean nest of Coptotermesspp. (reproduced from Hadlington, P., 1992)

Each termite species builds its particular typeof nest, either a mound nest (figs. 3-11 and3-12) made above the ground, or a sub-terranean nest (fig. 3-13) in a buried log, adecaying stump or the crown root of a tree, oran arboreal nest attached to a branch or tothe stem of a tree (fig. 3-14). Mound nestscan reach a height of up to six metres. Themound nest of the Australian species Ami-termes meridionalis is flattened and thetapered sides always orientate towards thenorth and south as shown in fig. 3-12.Constructing the nest this way ensures thatthe inside of the nest is not heated up by thesun since only the narrow sides are exposedto direct sun light. Subterranean nests buriedat a depth of 50 cm or even reaching depthsof several metres, are invisible and thereforedifficult to discover.

Fig. 3-14: Arboreal nest of Nasutitermes spp.(reproduced with permission from Hadlington, P., 1992)

3.2.2 Bees

Bees are the only insect tolerated in a closerelationship with man. Bees are always thegood characters in fairy tales and other storiesand a symbol for endeavour and industrialwork. As an utterly beneficial insect, beeswere domesticated by man since ages for theproduction of honey and wax. Thus bees wereintensively studied so that much of theircomplex behaviour is well elucidated. The


Fig. 3-15: Opened man-made bee hive of thehoney bee Apis mellifera showing an array ofhoney combs (reproduced from Clauss, B. & R., 1991)

importance of bees for some cultures isexpressed by the fact that in some Europeancountries a three year apprenticeship isrequired to become a certified tradesman inbee keeping.Bees live in nests, that are usually built from apaper-like material originating from chewedwood. The nests are either housed in aprotected opening such as a hollow tree, orsuspended from a branch. The honey combsinside the nest are made from wax and areused for the storage of honey and to house thebrood. Man provides artificial bee hives asshown in fig. 3-15 for domesticated honeybee species like as Apis mellifera. To collecthoney, the combs are removed from time totime and centrifuged. This procedure requiresa skilled and calm bee keeper to avoiddisturbance of the bees and the resultingpainful stings. Apart from honey and wax, thenutritious royal jelly has been utilised by manfor centuries in traditional medicine. It is aspecial diet for developing queens, made fromnectar and pollen.PNG has quite a potential for producing honeybut despite various organisations runningextension programmes, honey is produced inonly a few areas like Menyamya and Wau inMorobe Province and in the EasternHighlands Province.

A colony of the honey bee consists of 30,000to 50,000 individuals. Two distinct castes can

be found, the reproductive queens and dronesand the workers. The queen’s only task is tolay eggs. Her life span is four to five years.The haploid males, called drones, leave thenest where they were brought up and searchfor young queens to mate with. Once matingis over, the drones are thrown out of the nestand eventually die, since they are unable tocare for themselves. Therefore a drone issometimes called ‘flying penis’. The life spanof an adult drone is only a few days. Theexclusively female workers undergo a changeof specialisation during their life. During thefirst ten days after final emergence their taskis to care for the brood, ie. to feed the larvaewith honey and pollen. During the next stageof their life they produce honey from nectar,brought in by the collector bees. They alsobuild honey combs from wax, that is excretedby ventral glands on the abdomen. Later intheir lives, they dispose of rubbish from thenest, undertake their first flights in the vicinityof the nest and control incoming bees. The lasttask workers have to fulfil in their life ofseveral weeks is to collect nectar and pollenfrom the close neighbourhood of the hive orfrom flowers up to several kilometres away.All female individuals are diploid, the resultof sexual reproduction. The males arehaploid, derived from parthenogenesis. Thiskind of reproduction and sex determination iscalled haplodiploidy and is further outlinedin chapter 2.2.8. Unlike termites and othersocial insects, the castes of bees are deter-mined by the type of diet the developinglarvae feed upon. Larvae supposed to becomequeens are fed with royal jelly and are kept inspecialised cells of the honey comb. Thoselarvae bound to become workers are fed withhoney and pollen only.In a bee colony, consisting almost purely ofdiploid females, the driving force to developsocial behaviour is the fact that all workers aresisters, being more closely related to eachother than to a daughter or a haploid brother.

An example of the outstanding abilities ofinsects to communicate is the waggle danceof bees. A foraging bee having found a richsource of nectar or pollen performs this dance


in the hive upon arrival in order to let theother bees know where to successfully searchfor food. Fig. 3-16 A shows the round dance,that is performed, when the food is close tothe hive. The waggle dance (fig. 3-16 B) isperformed when the food source is distant andgives the direction for getting there. Theintensity of both dances indicates the amountof the food in the source: the richer the sourcethe more often the bee repeats the dance. Thewaggle dance is performed on the vertical partof a honey comb. The angle between theperpendicular line and the straight waggle lineof the bee describes the angle between the sunand the food source. As shown in fig. 3-17 A,the bee dances straight downwards, meaningthat the food source is in the oppositedirection to the sun. In fig. 3-17 B the anglebetween the perpendicular line and the bee’sstraight waggle line is 70°, indicating that thefood source can be found 70° left of the sun.

Fig. 3-16: The dance of the honey bee.(A) round dance, (B) waggle dance. See textfor explanation (reproduced from Ross, H.H., 1982)

In fig. 3-17 C the bee dances verticallyupwards indicating that the food source is inthe direction of the sun.Even if the sun is covered by clouds, the beescan still recognise the direction of the sun dueto their ability to see polarised light.

Fig. 3-17: The waggle dance of the honey bee Apis mellifera indicates the direction of the foodsource. See text for explanation (reproduced from Ross, H.H., 1982)

A B


3.2.3 Ants

All ant species are organised in colonies andtheir caste system is similar to bees. There areamazing and even incredible facts about thelife of ants described by Hölldobler, B. andWilson E.O. (Journey to the Ants - A Story ofScientific Exploration, 1994) and by Hoydt, E.(The Earth Dwellers - Adventures in the Landof Ants 1996). Referring to ants’ altruisticdedication to cooperation, the famousmyrmecologists Hölldobler and Wilson statein ‘Journey to the Ants’:

“It would appear that socialism reallyworks under certain circumstances. KarlMarx just had the wrong species”

According to the motto ‘all for one and onefor all’, cooperation enables ants to achieveaims that would be impossible for a single ant.Cooperation amongst ants can be easilyobserved in and on a nest of the arboreal redant Oecophylla smaragdina or kurakum. Assoon as a nest is damaged, for instance by anobject poked into the nest, an armada of antsappears to defend their home. At the sametime the ants start to fix the nest by weavingleaves together with a silken thread. Manyhands (or legs) cooperate to pull a leaf closertowards the nest, so that it can be tied andattached to the nest, as shown in fig. 3-18 A.If a desired leaf is more than one ant-lengthaway from the nest, the insects form longchains of several or more ants, to get the leafinto the right position (see fig. 3-18 B). And iftwenty or thirty ants are not powerful enoughto get the job done, then another hundred antsrush to assist. Large numbers of ants form‘wire-bridge’-like structures as can be seen infig. 3-18 C. These ‘bridges’ are not only usedfor towing on the ants’ construction sites, butare also formed to cross creeks or to con-veniently travel across gaps like from one treeto another. The worker ants do not have theability to spin a thread. This is done by theirlarvae, which are carried from the nest’sinside to where the silken thread is required.Some ant species have developed strange andbizarre forms of parasitism and mutualismas adaptations to nutrition. These include

Fig. 3-18: Cooperation amongst the arborealant Oecophylla smaragdina during the repairof their nest. See text for more details (photosSchneider, M.F.)

fungus farming, tending of plant lice and scaleinsects, slavery and stealing of food, socialstomach and mutualism with antplants.

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Fig. 3-19: Leaf-cutter ants supply their fungusgardens with pieces of leaves. The medium-sized worker cuts a leaf while the minorworker guards from parasitic flies that laytheir eggs on the ants (reproduced from Gullan, P.J.and Cranston, P.S., 1994)

FarmingSome ant species grow fungi in gardens, thatare either fertilised with the ants’ own faecesor with collected plant material. The latter isdone by leaf-cutter ants as shown in fig. 3-19.The fungi are harvested by ants as a source offood. The importance of the fungi for the antsis illustrated by the following example: aswith termites, a young winged queen takes apiece of the fungi cake into her mouth beforeshe leaves to found a new colony. Oncesettled down she inoculates plant materialwith the stored fungus.

Animal TendingMany ants live in close association with plantlice (Aphididae) or scale insects (Coccidae).By drumming on the tip of the aphid’sabdomen, the ant is stimulating the release ofsweet ‘faeces’, called honeydew. Honeydewis readily consumed by the ants. Sinceshepherd ants like this sweet pekpek verymuch, they watch their colony of aphids, sothat no other ants come to ‘milk’ their herd.Other species went one step further, and builtbowers for the aphids to live in. During winterin temperate areas, the aphids are brought into

the ants’ nest and taken back to their hostplant the next spring. The highest level isshown by some ant species that rear aphids orscale insects in their nest. The plant lice arebrought to their food plants in the morningand taken back to the nest in the evening. Incase of disturbance, aphids or scale insects aredefended by the ants. The queen takes afertilised aphid with her to found a newcolony. Fig. 3-20 shows scale insects livingtogether with their guarding ants in a hollowinternode of an antplant (myrmecophyte).

Guest AntsSome ant species with very small workersbuild galleries into nests of larger ants to stealtheir food. But not all species steal their food,some beg for it. Others live as parasites intermite nests. They avoid being attacked bythe termites by imitating the termites specificscent. This kind of defence strategy is knownas mimicry and uses allelochemicals (seechapters 3.1.3 and 4.4.5).

Fig. 3-20: Scale insects excrete honeydew asfood for ants. In return, ants provide shelterand care for their scale insects. In this case thescale Myzolecanium sp. (Coccidae) and theant Anonychomyrma sp. live together in ahollow internode of the antplant Kibara sp.(Monimiacaea) (reproduced from Gullan, P.J. andCranston, P.S., 1994)


Fig. 3-21: A specialised worker of thehoneypot ant Camponotus inflatus serving asa live honey storage container for the colony(reproduced from Gullan, P.J. and Cranston, P.S., 1994)

SlaveryParticular ants steal pupae of other ant speciesand take them to their nest. After the finalemergence of the slave ant, it has to do all thework like nursing the brood and cleaning thenest. Other species intrude into nests offoreign ants and bring along their own brood,that is then cared for by the foreign slaves.Queens of some species intrude into a nest,steal several pupae and keep them close tothem. After the abducted pupae have hatched,the slave ants have to tend the queen. Otherqueens move into the nests of the samespecies, kill the queen and take her place.Queens of particular other species intrude intonests of other species and decapitate (behead)the queen, a process, that takes several hours.The eggs laid by the intruding queen aretended by the slaves. The most alienatingexample might be the particular species of aslave-keeping ant, that produces onlyreproductive offspring. Workers of thisparticular species are not required any more,since workers of other species are used to rideon and to provide food.

Honeypot Ants as Social StomachSpecialised workers of honeypot ants serve aslive honey storage containers. Honey iscollected by normal worker ants and fed to the

‘honeypot’ ant. This animal holds the honey inthe considerably expandable abdomen, asshown in fig. 3-21. The ability to enlarge theabdomen to this extent is due to thestretchable arthrodial or intersegmentalmembrane. The honey is later released for theconsumption by other ants of the colony. Thetemporary holding pouch inside the gaster forfood that is later regurgitated and madeavailable for the rest of the colony is calledsocial stomach. Honeypot ants are not theonly social insects which share food withother individuals of their colony.

AntplantsApart from the close relationship between antson the one hand and aphids and scale insectson the other hand, another close mutualisticrelationship has developed between ants andantplants (myrmecophytes). Antplants possesscavities or domatia (‘little houses’), that arenot bored by ants or other animals, butindependently formed. Antplants mostly occurin the tropics and belong to various families.Acacia sphaerocephala (Fabaceae) provideshollow thorns and extrafloral nectaries forants, as shown in fig. 4-4. The relationshipbetween Kibara sp. (Monimiaceae), the scaleinsect Myzolecanium kibarae (Coccidae) andthe ant Anonychomyrma scrutator is shown infig. 3-20.Another outstanding example are ants of thegenus Dolichoderus. They live in domatiainside the tuber of about 80 different speciesof epiphytic antplants of the genus Myr-mecodinae belonging to the family Rubi-aceae. This type of antplant, shown in fig. 3-22, can be mainly found on New Guineaisland. There are a number of advantages ofthis close relationship between ants and theirrespective antplants. The antplants provideshelter and protection for the ants. Manyantplants release an unpleasant smell ofbutyric acid that might deter birds and otheranimals from probing for ants inside theantplant. Ants in return, provide nutrients andplay an important role for seed dispersal.Seeds of the antplants are collected by the antsand stored in special cavities of the antplant,until a suitable site for ‘planting’ is identified


by the ants. Usually a mature tree is chosen toensure that the bark doesn’t grow much moreso that the cast off bark including the attachedantplant doesn’t fall off. Apart from this, theants keep the antplant free of weeds and otherepiphytes and might defend their antplantagainst herbivores. Furthermore, the antsdispose of their debris like faeces, dead ants,etc. in ‘warty’ cavities of the antplant. Thenutrients of the decaying debris are incorpo-rated by the antplant. Antplants can be alsoinhabited by wild honey bees.

Fig. 3-22: A cross-section of the ant-epiphyteMyrmecodia spp. shows chambers inhabitedby ants of the genus Dolichoderus. See textfor more details (reproduced from Gullan, P.J. andCranston, P.S., 1994)

Further reading:

Abercrombie, M. et al. (19928): Dictionary of Biology;Penguin Books; London; UK

Atkins, M.D. (1980): Introduction to Insect Behaviour;Macmillan; New York; USA

Birch, M.C. and Haynes, K.F. (1982): Insect Phero-mones; Studies in Biology No. 147; Edward Arnold;London; UK

Clauss, B. and Clauss, R. (1991): Zambian BeekeepingHandbook; Forest Department; Ndola; Zambia

Commonwealth Scientific and Industrial ResearchOrganisation (CSIRO) (19912): The Insects ofAustralia - A Textbook for Students and ResearchWorkers; Volume 1 & 2; Melbourne UniversityPress; Carlton; Australia

Commonwealth Scientific and Industrial ResearchOrganisation (CSIRO) (19962): Insects - LittleCreatures in a Big World; CD-ROM; CSIROPublishing; Collingwood, Australia

Department of Agriculture and Livestock; Division ofPrimary Industries (1982): Bee Keeping; FarmingNotes 28; Konedobu; PNG

Drake, V.A. and Gatehouse, A.G. (1995): InsectMigration: Tracking Resources through Space andTime; Cambridge University Press; Melbourne;Australia

von Frisch, K. (1967): The Dance Language andOrientation of Bees; Belknap Press of HarvardUniversity Press; Cambridge; UK

Gullan, P.J. and Cranston, P.S. (1994): Insects - AnOutline of Entomology; Chapman & Hall; London;UK

Hadlington, P. (1992): Australian Termites and otherCommon Pests; New South Wales University Press;Kensington; Australia

Hermann, H.R. (ed.) (1981): Social Insects; severalVolumes; Academic Press; New York; USA

Hölldobler, B. (1984): The wonderfully diverse Waysof the Ant; National Geographic 165: 778-813

Hölldobler, B. and Wilson E.O. (1994): The Ants;Springer Verlag; Berlin; Germany

Hölldobler, B. and Wilson E.O. (1994): Journey to theAnts - A Story of Scientific Exploration; HarvardUniversity Press; Cambridge; USA

Hoydt, E. (1996): The Earth Dwellers - Adventures inthe Land of Ants; Touchstone; New York; USA

Lapedes, D.N. (ed.) (19782): Dictionary of Scientificand Technical Terms; McGraw-Hill; New York;USA

Lüscher, M. (1961): Air-conditioned Termite Nests;Scientific American 205 (1): 138-145

Michener, C.D. (1974): The Social Behaviour of Bees;Belknap Press of Harvard University Press;Cambridge; USA

Monteith, S. in Monteith, G. (1990): The Life inside anAnt-Plant; Wildlife Australia 27(4): 5

Naumann, I.D. (1994): Systematic and Applied Ento-mology - An Introduction; Melbourne UniversityPress; Melbourne; Australia

Pearson, I. (1978): English in Biological Science;Oxford University Press; Glasgow; UK

Roberts, M.B.V. (19854): Biology - A FunctionalApproach; ELBS; Walton-o.-T.; UK

Robinson, W.H. (1996): Urban Entomology - Insectand Mite Pests in the Human Environment;Chapman & Hall; London; UK

Ross, H.H. et al. (19824): A Textbook of Entomology;Wiley; New York; USA

Sammataro, D. and Avitable A. (1986): Beekeeper’sHandbook; McMillan; New York; USA

de la Torre-Bueno, J.R. (1989²): The Torre-BuenoGlossary of Entomology; The New York Ento-mological Society in Cooperation with theAmerican Museum of Natural History; New York;USA

Uvarov, B.P. (1966): Grasshoppers and Locusts: AHandbook of Acridology; Cambridge UniversityPress; Cambridge; UK

Winston, M.L. (1987): The Biology of the Honey Bee;Harvard University Press; Cambridge; USA

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