Instinct and Intelligence in Insects

Behaviour of insects is mostly instinct guided. A simple example of this is that of a mantid, reared in isolation from mother and other adults of her species, making an ootheca by shaping a solidifying liquid, coming out of her rear end, by beating it into a froth with her hind legs, and arranging it to cover her eggs. During making of the ootheca she does not look back. She has not seen another adult of her species making an ootheca. Still the ootheca, thus made by her, has the form and details characteristic of the species, to which she belongs. Role of instinct is obvious.

By instinct we mean a behavioural pattern, imprinted in the nervous system, and not learnt by the individual in its lifetime. Insects have been generally regarded as a programmed robot-like tanks with no intelligence. But in some cases we do get a glimpse of intelligence in insect behaviour We shall see a few examples of this.

In the chapter "Insects and Tools" the case of a sphecid wasp Ammophila has been described. It has been pointed out that, after digging a hole like nest in the ground, the female proceeds to collect a caterpillar, which will serve as food for the future larva. Before leaving on this mission, she conceals the nest by placing a pebble at its mouth, and then some loose earth over it. She then picks up a small stone, and hammers the loose soil to smoothness. She does not pick up just any piece of stone. She picks up a stone, weighs it, holding it between her mandibles, and may reject it. She then picks up another piece, and may reject this one too. Eventually she chooses a piece for smoothening the area with her nest. This choosing of a hammering implement seems to be an intelligence guided action. When she returns to the nesting site with a caterpillar, which has been paralysed by repeated stinging by her, she carefully opens the nest, drags the caterpillar into it, lays an egg on its body, and then again carefully closes and conceals the nest following the previous procedure. All this exercise to conceal the nest is to prevent a parasitoid from locating it and then entering it to lay its own egg.

Another sphecid wasp, the bee wolf (Philanthus apivorous), has a very similar nesting habit to that of Ammophila. But she provisions her nest with a paralysed bee and not a caterpillar. When, after digging and concealing a nest, she leaves for hunting a bee, she does not simply fly away. She flies in circles around the nesting site, as if she is carefully observing the land-marks around the nesting site, and then she leaves. In one experiment, the experimenter arranged a circle of pine cones around the place, where a wasp was digging a nest hole, and later, when the wasp was on her bee collecting trip, the arrangement of cones was removed some distance away from the nest. On return the wasp was unsuccessfully trying to locate the nest within the cone circle. This observation has convincingly demonstrated that the female wasp memorized the land-marks around the nest before proceeding to collect the larval provision. Memory is a necessary ingredient of intelligence. An intelligent creature remembers past experiences, the elements of which are reorganized to solve new problems.

It is a fairly common knowledge that the honey bee (Apis mellifera) worker, returning after foraging (i.e. in case bee collection of nectar and pollen), communicates to fellow workers the location of the feeding source by performing some rhythmic movements or dances. If the source of food is within 100 feet from the bee hive, the bee performs a round dance, in which she moves in a circle repeatedly, reversing the direction of her movement every time after completing a circle. This movement does not convey the direction of the feeding station; it merely communicates that the source of food lies within 100 feet from the hive.

If the feeding source is more than 100 feet away, the returning bee performs another variety of dance, the tail wagging dance. In this type of movement the dancer moves in two half circles alternately on the two opposite sides, the path of such movement looking like a flattened figure of "8". In this, in the straight part of the run between the two semicircles the dancer moves her abdomen from side to side; hence the name "tail wagging dance" given to this rhythmic movement. (To be more exact the distance of the nectar source, at which the round dance changes into the tail wagging dance is 120 feet for the Italian variety, and 275 feet for the Austrian variety of the honey bee — Frisch, 1962).

The tail wagging dance indicates not only that the nectar source is more than 100 feet away, it also conveys the direction in which the food source lies. If the dance is being performed on the horizontal landing board at the entrance of the hive, the straight part of the run directly points to the feeding station. Fellow bees, following the movements of the dancer, memorise the angle between the straight part of the run and the direction of the sun. Then they fly towards the food maintaining this angle between their direction of flight and the position of the sun. If, however, the tail swaying dance is done within the apiary on a vertical surface of the comb in the darkness of the hive, the direction of the feeding station is indicated in a different way. If the nectar source lies on the same side of the nest as the sun, the straight part of the run in the swaying dance is upward. If the sun is on the opposite side, the straight course is downward. When the sun is right above the head in the noon time, foraging and dancing do not take place. The angle between the direction of the straight course and the direction of gravity is memorized by the fellow workers, which maintain this angle between their direction of flight

— Fig. 9.1. Dances of the honey-bee. a: tail-wagging dance; b: round dance.

— Fig. 9.1. Dances of the honey-bee. a: tail-wagging dance; b: round dance.

b a b a and the sun's position, when proceeding for foraging. Thus in the darkness of the apiary, as the sun is not visible, the angle is indicated by the dancer with reference to the direction of gravity, and the fellow workers "translate" this angle with reference to the direction of the sun.

The tail wagging dance not only conveys the direction but also the distance of the feeding place. The farther the source of food, the more slowly the dance is performed. Thus, when the food is at the distance of 1000 feet, an Italian bee (Apis mellifera liguistica) performs the tail wagging runs 6.4 times in 15 seconds, and, if the distance of the feeding station is 2000 feet, this number is reduced to 4.5. When the dance is performed more slowly, the abdomen swaying takes place with greater frequency per second. As one author has pointed out, "one additional swaying movement per second corresponds to an increase in distance by every 75 metres".

The flexibility and variability of the dancing behaviour of the honey bee suggests involvement of intelligence. But Karl von Frisch, the Austrian scientist who discovered and extensively worked on language in bees, has pointed out that he and his team have removed honey combs from the apiary, and have reared the workers out of contact with older adults, but have found that when the workers reared this way were brought into the apiary, they could immediately indicate position and distance of food through their dancing, and could successfully comprehend what a returning foraging bee tried to convey through her dancing. It means no learning was needed to correctly perform and understand the dancing sign language. K. von Frisch has, therefore, inferred that the language of the bee is truly "innate", i.e. instinctive. But memory is involved in bee's language. A returning foraging bee has to remember the angle between its path and the sun's position. Similarly the fellow workers, closely following the movements of a dancing bee, have to memorise the angle being indicated by the dancer for guidance of their own foraging trip. As has been pointed out earlier, memory is a necessary associate in the functioning of intelligence. Thus, there is a glimpse of intelligence in the bee communication.

The instances, described above, show that some intelligence is mixed with largely instinctive behaviour. But these are not all. Many more instances may be pointed out. All social insects (bees, wasps, ants and possibly termites) show some learning and decision making. Cockroaches learn finding their way in mazes, after some initial trial and error, and ants learn to take the shortest way to food. That, besides their instinctive behaviour, insects have some learning capacity has to be accepted (Papaj in Resh and Carde, 2003). Learning involves, some deviation from pure instinct. At least two books have been written on insect learning (Abramson et al, 1990; Papaj and Lewis, 1993). According to Papaj (in Resh and Carde, 2003), insect learning has been documented in eight different fields in all major insect orders, viz. water consumption, mate finding and choice, territoriality, predator avoidance, dispersal, migration, kin recognition, and thermoregulation. Learning is most pronounced in social insects, but it could be detected in other insects too. In experiments on stored grains beetle Tenebrio and in the fruit fly Drosophila it has been inferred that the memory, formed in the larval stage, persists through metamorphosis in the adult stage. Many insects learn to avoid toxic food. Butterflies learn to land on the leaf shapes of their host plants, and may wrongly land on other plants having similar leaf shapes. Bees readily learn to associate presence of food through the scent and colour of flowers. They may show some cleverness too. Some insect pollinators may learn to feed on nectar without doing the return favour of pollination. One of us (PJ) has observed in Brazil Xylocopa bees making holes in corollas of Hibiscus-like flowers to get nectar without visiting stamens and pistils.

About forty years ago, some experiments were performed with flat worms or planarians (McConnell, 1962; Jacobson, 1966). These worms are known for their remarkable capacity of regeneration. When the body of a flat worm is crushed into tiny pieces, even if single cells get separated, a fragment, however small, regenerates into a complete worm. In the experiments some worms, which had been taught to avoid light or electric shock in mazes, were crushed almost to the cellular level, and the resulting debris was fed to some new worms. It was claimed that the fed worms, without any training, showed the conditioned reflexes, which their "food" had acquired through training. Such claims led people to say jokingly, "Students will have to eat their professors to get knowledge". But such experiments could not be satisfactorily repeated; and therefore, the claims were rejected. Similar experiments, leading to similar claims, were made using other stimuli. They, too, could not be verified satisfactorily. Fortunately, no such viable experiments with insects have come to light. Perhaps, such experiments should be one day repeated, also with some famous prolamarkian experiments, just to prove they are wrong or they are crazy. Who among young scientists will lose time over what seems fully wrong?

Birds, mainly crows, are known to count up to eight, when there are hunters hidden inside a building. Some crows, like the neocaledonian genus, are known for their intelligence, namely in tool making. Probably insects cannot count. People in Papuan tribes, on the higlands of New Guinea, were said to count one, two, three, many. Some Amazonian tribes also were not supposed to go above two. However, PJ noted that tribal youths in New Guinea, undergoing education, picked up modern mathematics very well. Children of the above mentioned American Indians had no difficulty with calculation. This observation shows how important learning is in development and manifestation of intelligence. Insects, in their way, do show some capacity to learn.

As we learn more about insect behaviour, we may come across more instances of mix-up of instinct and rudimentary intelligence.

References

Abramson, C. I., Yuan, A. I. and Goff, T. 1990. Invertebrate Learning. A source book. Am. Psychol. Ass., Washington, DC. Frisch, Karl von, 1962. Dialects in the language of bees. Scientific American 207 (2): 78-87.

Jacobson, A. L. 1966. Chemical transfer of learning. Discovery 27 (2): 11-16. McConnell, J. V 1962. Memory transfer through cannibalism in Planarians. Journal of Neuropsychiatry 3 (51): 42-48. Papaj, D. R. and Lewis, A. C. (eds.) 1993. Insect Learning: An ecological and evolutionary perspective. Chapman and Hall, New York. Resh, V H. and Carde, R. T. (eds.). 2003. Encyclopedia of Insects. Academic Press & Elsevier, Amsterdam, Holland : 1266 pp.

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