THE BIG COMPANY OF WOOD-EATERS: THE TERMITES

TERMITES possess a social life parallel in many ways to that of the ants. They cultivate mushrooms, for instance, and keep many different species of guests. The males and females fly away into the air together, but they do not mate in the air as many ants do, but descend again to the ground to do so. As with ants, the colonies of the more primitive species consist of a few, or very few, individuals, living a more primitive life, whereas the more highly specialised ones may consist of enormous numbers of individuals, living a much more elaborate and specialised life. But the termites are much more primitive creatures than ants, and have a more primitive structure.

They possess some characters similar to those of cockroaches, and are considered to be descended from an ancestor common also to those creatures. In the tropics where termites are most plentiful they are extremely destructive to all woodwork, books, or anything which contains cellulose, of which they are very fond; but wherever they are they destroy woodwork. They consist of males, females, and workers, as with ants; but they are divided up into many more castes. Wheeler gives five castes which he classifies as follows :

I. First form adults, called kings and queens. They are very similar, deeply pigmented insects with large compound eyes, large brain and frontal gland, well-developed reproductive organs and at first with well-developed wings. The wings, however, later break off at pre-formed joints at their bases and are discarded. Old individuals of this caste, therefore, can always be recognised by their short wing-stumps.

2. Second form adults, complemental and substitutional kings and queens, only less pigmented, with wing pads or imperfectly-formed wings with which they cannot fly; brain, compound eyes, frontal gland and reproductive organs somewhat smaller than in the first form.

3. Third form adults called worker-like, substitutional, or complemental kings and queens. Scarcely pigmented, entirely wingless. Brain small; eyes and frontal gland vestigial; mature reproductive organs smaller than in the second form.

4. Workers. Wingless, unpigmented; brain, small; compound eyes and frontal gland extremely small, or absent; reproductive organs rudimentary, as the workers do not reproduce. Head broader than in the first and second adult forms.

5. Soldiers. Wingless; head large and more or less pigmented; brain very small; compound eyes vestigial; frontal gland, and in very many species the jaws and jaw muscles large. In a few genera the soldier caste is represented by a different form, usually smaller than the worker, with a retort-shaped head, produced in front in the shape of a long, tubular snout, with the opening of a large frontal gland at the tip.

THE TERMITES’ CASTE SYSTEM

THE castes vary in the different species, and there may be two or three different forms of soldiers and workers present in one colony. Thus there could be sixteen different kinds of individuals present, though it is probable not all occur at once in one colony. Five or six, however, of the following are often to be met with in a single colony :

1. First form males and females

(true kings and queens).

2. Second form males and females.

3. Third form males and females.

4. Large male and female workers.

5. Small male and female workers.

6. Large male and female soldiers.

7. Medium-sized male and female soldiers.

8. Small male and female soldiers.

It has recently been shown that the castes appear to be determined in the egg, and not by special feeding alone. The first form males and females can reproduce themselves, and all the castes beneath them; but the second and third forms can only reproduce themselves and soldiers and workers.

A termite colony is founded as follows. The winged kings and queens rise into the air for a short flight, and then descend to the ground and get rid of their wings. The male termite then runs after a female and when she has found a suitable spot they both dig together to excavate a cell. When the cell is completed, mating takes place; the queen lays eggs and a small colony is started.

THE TERMITE THAT LAYS A HUNDRED MILLION EGGS IN some species the king and queen are kept in a special cell, when they are fed and attended to by the workers. The queen is fed very freely, and her body becomes enormous in size, being distended with fat and eggs. She lays eggs every few seconds, and it has been estimated that the number of eggs laid by her in one day is 30,000 and a hundred millions during her lifetime. Should the king and queen happen to die, the second or third form adults are substituted for them. The workers spend most of their time in feeding and cleaning their fellows and in repairing the nest. The soldiers protect the nest with their jaws, and those with snouts do so by ejecting a paralysing secretion.

Termites eat large quantities of wood, but also are fed by their fellows with saliva, with half-digested food, and with excreta. Further, fatty substances exude from parts of the body and these are licked up by other individuals. The queen produces most of this substance and the workers are continually licking her and even bite tiny bits out of her skin to make it flow.

It is a curious fact, which has been thoroughly demonstrated by experiment, that termites are unable by themselves to digest the cellulose obtained from wood, and are only enabled to do so by the presence of a number of protozoa in their intestines. In different species of termites, different species of protozoa occur. The protozoa in the intestines of a termite can be killed off by keeping the host in a temperature of 360 C. for twenty-four hours. If the termite is then fed with a diet of wood it will die in about fifteen days, but if given digested wood or fungus-digested cellulose, it will live indefinitely.

Some species only bore galleries in wood or in the soil, but others build elaborate dwellings, using nest materials which are very hard and strong to resist the attacks of ants and other enemies. The nest materials consist of wood or soil, fastened together by saliva, or of foods which have passed through their bodies, and also of food partly digested and then brought up again. These materials, when dry, form a substance as hard as cement. There are very many different forms of nests, but the termites do not leave entrances and exits as do ants. The nests are entirely closed in, as darkness and no draughts are essential to the well-being of termites.

The fungus gardens in a termite’s nest are somewhat similar to those of ants, but the substratum on which the fungi are grown consists of vegetable matter, cut up, eaten, and passed through their bodies. The newly hatched young are kept in the fungus gardens where they devour the food portions of the fungus. Only the first three adult forms are fed with the fungus; the soldiers and workers do not feed on it. Many other creatures live in termites’ nests, including a certain number of species of ants, and termites of other genera. They steal from their hosts, living apart in the galleries of the nests, and are hostile lodgers.

There are also many other guests which fall under similar categories to those of ants. The most interesting point in connection with many of these guests is that they possess enormously developed hind bodies, with extraordinary finger-shaped processes which exude fatty substances. Various two-winged flies, and beetles with short wing-cases may be mentioned among others that produce these exudations which are greedily devoured by their hosts.

WHAT TO READ NEXT ABOUT ANIMAL SOCIETIES ANIMAL ECOLOGY by Charles Elton (Sidgwick) is a very useful Text book and can be thoroughly recommended to anyone who wishes to learn something more about the social life of animals. It is clearly written and not too long. For anyone who is anxious to learn all about the social lives of insects The Social Insects by W. M. Wheeler (Routledge) is essential. It is written in a most interesting as well as lucid style and likewise deals with everything on the subject. Animal Ecology by Roy Chapman (McGraw) is a very large book and is recommended to the more advanced students; Laboratory and Field Ecology by V. E. Shelford (Bailliere) is also a large work which will repay very careful study. It contains a very complete Bibliography.

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