Insects and Tools

Man may be described as the tool wielding animal. Much of his civilization built up, including writing and literature, has been through extensive use of tools and implements.

At the outset let us make clear to ourselves what a tool is. The generally accepted definition of a tool is that it is a foreign object, that is an object outside the body of the user, which is used as such or with modifications to increase the mechanical efficiency of the user. Perhaps the "mechanical efficiency" part of this definition should be replaced with "working efficiency", as a computer is not exactly an artefact for increasing man's mechanical efficiency. Beck (1980) has pointed out the following qualifications for a tool: first the object forming the tool must not be a part of the animal's body; secondly it must not be attached to the environment (climbing a tree is not a use of a tool); thirdly, the user must manipulate the tool and achieve something useful with it. The spider Dinopis throws its web at passing insects and so qualifies as a tool user, but the web of a spider, attached to the substrate, is not a tool. This description of a tool by Beck better defines the "tool" than the simple definition, given above.

Though making and wielding of tools is a characteristic of man, instances of use of simple tools by some other animals are also known. Apes are known to use a twig, stripped of leaves, for catching termites for food. If the bank of a stream is so high that a chimp cannot lower his mouth to the water level, he is said to collect some dry leaves, crush them with his hands into a spongy mass, dip the mass into water, then hold it above his mouth and squeeze it to drip water into the mouth. A Galapagos finch uses a twig, held in its beak, to dislodge insects from crevices in a tree to feed upon them. Meia crabs brandish the sea anemone, Actinia, on their claws to paralyse their preys. Egyptian vultures use stones to break eggs too strong for their beaks. Some octopi slip a stone between a mollusc's valves to prevent their closing. Herons throw objects, even flies, into water to attract fish. Sea otters commonly use tools to open shells, which are flat stones held against their chest, when they are swimming with their belly uppermost. Many other cases of tool use among vertebrates and invertebrates could be cited. A particularly notable example: crows of New Caledonia are known to make an interesting insect catching device (Hunt and Gray, 2003). They cut a twig, remove leaves from it, make a notch near one end of the twig, and then bend the shorter part of the twig to make a hook. This hook is used to collect insects from crevices in the tree trunk. Some white dolphins of Australia hold marine sponges in their mouth for foraging. Young dolphins learn this use of a tool from their mothers.

Cases of use of tools are known among insects, too. Jean Henri Fabre (1908), a well known French entomologist and a contemporary of Louis Pasteur, made some very interesting observations on the breeding habits of the wasp Ammophila. His observations have been repeated by Peckham and Peckham (1898) and a number of other entomologists. A female of Ammcphila, before laying an egg, makes a small tunnel in the ground, using her mandibles and bristly legs (see the chapter "Instinct and intelligence"). This tunnel is a little wider at its inner end, which will be the egg chamber. Before laying an egg in this chamber, the female proceeds to provision it, so that the larva, hatching from the egg, will find its food in immediate vicinity. The larval food is a caterpillar, which has been made insensitive by repeated stinging by the mother. But before leaving to collect a caterpillar, she closes the nest carefully, so that a parasitic insect does not lay its eggs in the nest. The Ammophila mother goes through an elaborate procedure to make the nest safe. The mouth of the tunnel is made funnel shaped, a pebble is placed in the funnel, so that the tunnel mouth is closed. Then she scatters the loose earth, which was removed during the making of the tunnel, over the opening of the nest, and then proceeds to do something incredible. For effectively hiding the nesting site, she smoothens the loose earth over the nest. For this she picks up a pebble between her mandibles, and allows it to drop on the loose soil repeatedly. Thus the disturbed earth is hammered to relative smoothness.

Next the female proceeds to cut pieces of grass and scatters them over the nesting site to camouflage it further. When the mother returns with the caterpillar, she opens the nest carefully. After pushing the caterpillar into the nest, and laying an egg on the body of the caterpillar, she closes the nest following all the steps of the earlier procedure. Using a small stone for hammering down the earth is an instance of using a tool.

Some ants, for example Oecophylla smaragdina in Asia and Oecophylla longinoda in Africa, make vessel like nests, hanging from trees (Jolivet, 1991). The vessel is made up of some leaves of the tree joined together at their edges. For joining the leaves, worker ants hold edges of two neighbouring leaves close together using their legs and mandibles. Another worker holds a mature larva of its own colony with its mandibles. The larva, when ready for pupation, actively produces silk like material from large glands, situated close to its mouth. The silk is for making a cocoon around the pupating larva. The silken thread, emerging from the mouth of the spinning larva, is made to stick to the marginal parts of the two leaves alternately by movements of the head of the worker ant. Thus the edges of the leaves are "stitched" together, and for this purpose the spinning larva is used as a living shuttle. Through cooperative efforts of the workers more leaves are joined together to make a vessel like nest. Thus, the pupating larva is used as a tool.

Some ants, belonging to the genera Aphaenogaster and Pogonomyrmex, feed their larvae with liquid nourishment, obtained by pressing together bits of leaves. Often hard particles of earth are mixed with the bits of leaves to improve extraction of the liquid larval food (Jolivet, 1991). Ant workers also use leaves as tools to carry large quantities of food, like jelly or any other semiliquid material. Generally, ants are good mothers taking care of their brood and practice social food transfer. The Dracula ant queens, Mystrium and Amblyopone, in Madagascar, are an exception: they suck hemolymph from their own larvae! They practice a form of nondestructive cannibalism and are exclusively dependent on those larvae as a food source (Goodman and Bernstead, 2004), but, as has been said, it is a case of cannibalism and does not come in the ambit of tool use.

A reduviid bug from Costa-Rica, Salyarata variegata, feeds on termites, dwelling in dead and rotting tree branches. The bug uses tools in two ways: to provide camouflage and to bait termites. The nymphal S. variegata coats itself with crumbs scraped from the termite nest (McMahan, 1983). Its mode of catching the prey is interesting (Pierce, 1986). It searches out a hole leading into the termite galleries. It approaches the hole cautiously, catches a termite, and immediately withdraws. After sucking up the body fluids of the prey, it moves towards the same hole, holding the carcass of the prey between its mandibles. This time its movement is nonchalant and casual. It drops the carcass, which is readily accepted by termites as food, as they are scavengers or saprophagous. The bug again catches a termite, withdraws, sucks its nourishment, and returns to the nest with prey's carcass. The process is repeated, and termite after termite get killed. The bug's second and the following approaches to the termite nest are obviously not burdened with caution; perhaps it is because the predator offers the dead prey's body as a bait to the termites in these visits, and also perhaps because it has acquired the characteristic odour of the termite colony. Thus it seems to be a case of using a dead termite's body as a tool for raiding prey's habitat. Probably also it is a genetically fixed sequence which evolved because it was successful. The bug can capture 31 worker termites within three hours! In Australia, a predatory spider, Cosmophasis bitaeniata, resembles to its prey, the ant Oecophylla smaragdina. The spider acquires the cuticular hydrocarbons of the prey by eating the larvae (Elgar and Allan, 2004). This case of using one's prey for enhancing one's mimicry may be taken as a case of tool use, only by expanding the meaning of a "tool".

In Florida owls stand at the entrance of their burrows, surrounded by dung that is positioned to entice beetles (Phaneus igneus) to come (Levey et al, 2004). They capture many insects that way. This study builds an elegant case that the owls are using the dung as a tool. Also, web-building spiders attract prey by storing decaying matter (Bjorkman-Chiswell et al, 2004). In Australia, Nephila edulis incorporates into its web decaying animal and plant matter to attract blowflies, Lucilia cuprina. The spider replenishes the debris when necessary. These are cases of nonhumans using tools for catching insects, like the examples of chimps and a Galapagos finch using shoots to collect termites and other insects.

Larvae of neuropterans, belonging to the family Myrmeleontidae, are peculiar looking plump creatures, with long sickle shaped mandibles and forward directed long legs. Larvae of many myrmeleontid species make a funnel shaped depression in fine grained or dusty soil, and remain buried at the bottom of the pit. When a passing ant happens to move close to the pit, and soil particles, disturbed by its movements, roll down the funnel, and the larva at the bottom perceives possible presence of a prey, it immediately comes up from the resting position, throws some sand towards the prey, and catches the ant with its mandibles, and feeds upon it. Thus these larvae make and use an interesting trap for catching ants, and they throw sand to prevent escape of the prey. Myrmeleontid larvae are also known as ant lions. Larvae of Diptera, Rhagionidae (Vermilio and Limpromyia) show a similar prey catching behaviour.

Larvae of caddis flies (Trichoptera) are aquatic and caterpillar like, with well developed thoracic legs. They make a thimble like silken case. Abdomen and some of the thorax remain within the case, while its head, part of thorax and legs protrude beyond the opening of the case during normal movements. The larval case is strengthened, by including in the silken material, pieces of leaves, twigs, sand grains or small pebbles. Every species makes a characteristic larval case.

Protecting and/or camouflaging with the help of material, present in the surroundings, is seen in many insect larvae. Larvae of many species of tortoise beetles retain exuviae of the previous instars or fecal discharge or both at the end of the abdomen forming a protective shield. Many Cassidinae use this tool in defense against potential predators. The shield is maneuvered in the direction of the attacking insect, and this wielding of the shield is generally successful in repelling the predator. Removal of the shield renders the larva highly vulnerable to predators, which are mostly ants and bugs.

Webs and nets of spiders for catching prey may in some way be regarded as tools (but it is not a tool, as per the limits defined by Beck, 1980). Some spiders, like the Pasilobus, throw their "bola" (a large sticky droplet at the end of a silken thread), like the South-American gauchos, to catch their prey.

Pierce (1986) has mentioned the following instances of tool use by insects:

01. Weaver ants using conspecifics as a gluing mechanism.

02. Ants crossing a streamlet with a bridge made of linked fellow ants.

03. Nuptial gifts by male empidid flies.

04. Foraging female water striders, while copulating, provides a free ride to the male.

05. Use of sand/soil for food transportation by ant.

06. Soil/stone dropping behaviour by some ants.

07. Sand throwing by ant-lion and worm-lion.

08. Nest closure by Ammophila and Sphex wasps.

09. Camouflage/Bait to capture a prey by the assasin bug.

10. Fecal shield defense by Cassids.

11. Sound baffle use by Oecanthus crickets.

12. Structure building by many species (termites, bees, etc.).

Only 5 to 10 of the above items have met with a general acceptance of entomologists. Some reject, others accept some of the other activities (1 to 4 and 11 and 12) as a case of tool making and using. Let us explain what sound baffle means. The male of some crickets (Oecanthus) are able to increase the effectiveness of their calling sound by gnawing a small hole in a leaf and orientating it in front of their body (Beck, 1980). The leaf acts as a baffle. Structure building is more questionable in its interpretation as tool making. Perhaps, some justification for regarding nest making as a case of tool making lies in the fact that many insect species fashion structures (burrows, nests) to serve diverse functions (thermoregulation, accoustics, etc). That seems more of an instinctive behaviour than guided by intelligence. Soil or stone dropping has been observed among several ants. Dolichoderine ants (£onomyrma bicolor), for instance, surround the nest of ant competitors and drop small pebbles and other objects down the entrances. Holldobler and Wilson (1990) point out that, in the deserts of Arizona, workers of C. bicolor inhibit foraging of a species of Myrmecocystus by dropping pebbles into their nest.

One important difference between tools made and used by man and those used by other members of the animal kingdom, including insects, is that the latter are objects in the surroundings, which are used either as such or slightly modified. The former, however, are generally extensively modified to suit human requirements. Even a bow and arrows are much more altered external objects than twigs, with leaves removed, used by chimps or bent twigs, used by the New-Caledonian crows, for collecting termites or other insects. Railway locomotives, aeroplanes and computers are some examples of artifacts, which are very extensively and intelligently modified external objects, standing in stark contrast with simple tools, used by insects and other animals.

One objection raised to regarding external objects, used by insects and other animals as tools: tools and implements, made and used by man, are made and used intelligently, but animal tools are used instinctively, i.e. as per inherited behavioural pattern or as per behaviour programmed in the genome. But this objection is perhaps not as serious as it appears at the first sight. Glimpses of intelligence do appear in insect behaviour (see the chapter on "Insects and intelligence").

There is no doubt that intelligence is greatly developed in man, and human behaviour is largely guided by his intelligence. But glimpses of intelligence may sometimes be seen in animals using their mechanical devices. In its breeding behaviour the Ammophila wasp, the case of which has been described above in this chapter, the female does not pick up just any pebble to hammer the loose earth. Before finally choosing a pebble, she holds and weighs several pebbles between her mandibles, and rejects them. The reduviid bug, preying on termites in rotting wood, changes its behaviour as per varying state of rotting in the wood. Recent studies on wild chimp behaviour show that at least 39 aspects of behaviour are passed on to the progeny "culturally", that is through learning and training. One such behaviour concerns termite feeding. Chimpanzees in the Gombe National Park in Tanzania, as observed by the renowned zoologist Jane Goodall, use a long twig, stripped of leaves, for catching termites. When the termites are crawling all over the twig, the chimp with one hand removes all the termites, presses them into a ball, and transfers the ball to its mouth. But elsewhere chimps use shorter twigs, and pick up the termites from the twig with their lips, a much less efficient method. This behavioural difference seems to be through learning, which is a necessary corollary of intelligence.

Georgia Mason (1991) insists that individuals in a group can benefit from the experience of those around them. That is why birds flock, fish school and mammals gather in herds. So did the dinosaurs during the Mesozoic and they were not the stupid animals, with a small brain, as pictured in the past. The group learning in chimpanzees has been referred to by a naturalist in good humour as "tool training at the chimp academy". Recent papers on fishes, birds and insects show that tool use is more prevalent than previously believed.

In our opinion, there is not enough ground for sharply distinguishing tool using by animals and that by man. Often intelligence and instinct are mixed up. An example of this situation has been described by Bateson (1983). He says: "It is possible to take a recently hatched laughing gull (Larus articillà) chick and show that it will peck at models of adults' bill. Advocates of the first view (that innate behaviour is entirely inborn with no place for learning) would almost certainly want to call the behaviour innate, since the chick had previously been isolated from 'relevant' experience. Nevertheless, as the chick profits from its experience after hatching, the accuracy of its pecking improves, and the kinds of bill like objects it will peck at are increasingly restricted".

However, it has to be accepted that making and wielding of tools and implements among humans is almost entirely intelligence guided and, therefore artefacts present numerous modifications and versions with variations in needs and local practices and conditions, while use of tools by animals is mostly innate or instinct guided, and, therefore, they tend to be stereotypic within a species. The greatly developed intelligence in man and his nimble prehensile hands make all the difference. With his technological development man has started thinking of producing "cyborgs" (Cyber-organisms), that is producing humans with implanted electronic chips, which will guide his functioning, including mental working and memory. With successful implantation of foreign objects, foreign to his body, like kidneys, liver, heart and orthopaedic implants, he is already moving towards the imaginary cyborg, and moving away from other organisms including insects. Should we regard such implants as "internal tools"? Let biology philosophers decide on this.

Andrée Tetry (1948) produced an important book, "Tools among Living Beings" (English translation of the French title). In this work, the author regarded even functional parts or organs of an organism, such as "ruptor ovi" or egg bursters of a newly hatched insect larvae or the press stud (a snap fastener) of the octopus, as tools. Frish and Otto (1974) wrote also a book in the same sense, showing the basic of animal architecture. But in the present treatment we have adhered to the limits of "tools" as described by Beck (1980). "What's so special about using tools?" said Michael Hansell (1987). "Even a simple amoeba eventually could use tools during phagocytosis". However, man was named Homo faber by Henri Bergson, complimenting his capacity of intelligent fabrications.

It is also evident that false eggs on Passiflora coerulea to prevent Heliconius butterflies to lay eggs on the plant are not tools and they are integral part of the vegetal (Sacchi, 1988).

A mature

Silken thread |arva holding |eaves producing leaves together. s||k

A worker holding a silk producing larva.

A mature

Silken thread |arva holding |eaves producing leaves together. s||k

A worker holding a silk producing larva.

— Fig. 11.1. Weaver ants "sewing" together leaves to make a nest.

A worker using its mandibles to bring margins of leaves closer.

A worker using its mandibles to bring margins of leaves closer.

— Fig. 11.1. Weaver ants "sewing" together leaves to make a nest.

' .. funnel like depression

" made by the larva by is^vVC-i- -r-: V; •' -- - rubbing its plump body against loose sandy soil

— Fig. 11.2. A vertical cut through an ant-lion trap for catching ants.

— Fig. 11.3. False eggs on Passiflora (Granadilla) coerulea in Tucuman, Argentina. The pseudo-eggs prevents Heliconius butterflies from laying eggs on the plant (after Sacchi, 1988).

— Fig. 11.4. Ammophila urnaria using stone to pound down earth over nest (after Peckham and Peckham, 1898).

— Fig. 11.5. Pompilus quinquenotatus digging nest (after Peckham and Peckham, 1898).


Bateson, P., 1983. Genes, environment and development of behaviour. In: Animal Behaviour, vol III (Genes, Development and Learning) (Editors: T. R. Halliday and P. J. B. Slater). Blackwell Scientific Publications, London.

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Madagascar. The University of Chicago Press, Chicago and London: 1709 pp.

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Jolivet, P., 1991. Curiosites Entomologiques. Chabaud, Paris: 170 pp.

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Sacchi, C. F. 1988. Ricerche sulla struttura degli ecosistemi: Invito al «cenone ». Thalassia Salentina 18: 187-276.

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