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MAN’S habits change more rapidly than his instincts. To-day we are born with instincts appropriate to our palaeolithic ancestors, and when we follow our instincts alone we behave in a palaeolithic manner. It is probable that primitive man, like a wild animal, ‘knew’ pretty well what was good for him in the way of food. Modern man does not, and when he does he cannot get it. Sedentary workers consume meals appropriate to hunters. Women of fashion attempt to supply the energy needed for dancing by the ingestion of large amounts of chocolate. Man, in fact, must use his reason to arrive at an appropriate diet. But the members of insect societies have solved a similar problem on instinctive and physiological lines. They have brought about the best possible division of a communal food supply by methods which, if strange and often disgusting to human minds, are as effective as any system of food control invented by man.

Let us see what are the prerequisites of a rational distribution. Apart from water, salts, and vitamins which are only required in tiny quantities, foodstuffs may be classified as carbohydrates, fats, and proteins. Carbohydrates include sugar, starch, and the like, fats embrace the chemically similar oils and waxes. Neither contain nitrogen or sulphur, and they are mainly useful as fuel; that is to say in order by combining with oxygen to give up energy which can be used by the animal for heating itself, or working its muscles and other organs. The proteins, on the other hand, are required to build up the living tissue during growth, and repair it after injury or the wear and tear of everyday life. If we compare the requirements of an animal and a motor vehicle, water serves the same function in both, of cooling and carrying away unwanted substances, carbohydrates and fats correspond to petrol, proteins to spare parts, and probably vitamins to lubricating oil. As a matter of fact proteins can act as a source of energy, just as spare woodwork for a train could be used as fuel, but most animals find them unsatisfactory as the sole source.

It is clear that a growing animal needs relatively more proteins than an adult. A baby lives on milk which an adult would instinctively supplement with starchy foods. But the baby requires, and finds in the milk, some fat and carbohydrate as fuel to keep itself warm and work its tiny muscles. The wasp grub is cold-blooded and sluggish. It requires very little but proteins. And the adult worker with its short life of intense exertion needs little protein but plenty of fuel. Hence, even though the food which the workers give to the grubs consists very largely of chewed-up flies, it contains more carbohydrate than necessary. When a worker comes to feed a grub by regurgitation from its crop the grub thanks it by secreting a drop of fluid containing sugar for which it has no use, but which is valuable fuel for an active insect.

The bees have taken things a stage further. Their sources of food are the nectar of flowers, a nearly pure solution of sugar in water, and the pollen, which consists largely of proteins. Even from the same flower one bee never collects both nectar and pollen. And in the hive the nectar is stored as honey, and the pollen separately as ‘bee-bread.’ The honey is used primarily as a source of energy and heat during the winter, the bee-bread along with some honey as food for the grubs. What is more remarkable is the fact that a grub gets a different mixture according to its future career. Queens and workers come from fertilized eggs, drones from unfertilized, but the difference between queens and workers seems to be determined by the type of food given to the larva. So that in the hive food control is also birth control.

The most bizarre system of all is found among termites. These insects live almost entirely on wood, which most animals cannot digest. Strictly speaking the termites cannot do so either, but their intestines contain protozoa which can, just as the horse and cow digest their hay with the help of bacteria. There is evidence that these or other organisms in their bodies can even fix atmospheric nitrogen like the bacteria found in the roots of leguminous plants, thus dispensing with the need for proteins in the diet of their hosts. But this digestion is too slow a process to come to completion in the body of a single insect, so the partially digested excreta of one are eaten by another until the process is complete, and the final indigestible residue is also so incapable of putrefaction that it can be used for nest-building. This apparently repulsive process only corresponds to the passing on of half-digested food by one segment of our intestines to the next. A single termite has not a long enough intestine for the whole process. But it is only certain of the termites that can take part in wood digestion. Besides queens and males the termite nest usually contains several different castes of workers and soldiers with large jaws. These jaws are too clumsy to allow of wood-chewing, so the soldiers are fed by the workers with so-called saliva, as is the queen.

Termite societies therefore rest on a basis of physiological functions and of instincts, each one as complex and highly organized as those which form the basis of the relationship between a mammalian mother and her children. But alas, insect societies are no more perfect than human, and parasites can as easily find a place in an economic system determined by instinct, as in the products of intelligence, enlightened self-interest, or whatever else is at the basis of human economics. Whether the correct form of demand for food in an ant’s or termite’s nest is a gentle stroking of the donor, an offer of a drop of some sweet secretion, or what not, some unprincipled insect will generally be found to make it. Students of human society will compare these parasites with brewers, burglars, bolsheviks, bankers, bishops, or bookmakers according to their tastes. Occasionally they are of some value to the community, for instance by joining in its defence, generally they are useless, so far as we can see; and often they devour not only food, but larval ants.

Humanity is engaged in the awkward passage from an instinctive to a rational choice of food. ‘A little of w’ot yer fancy does yer good’ is no longer a sufficient guide for us, as it is for the insects, and we do not yet know quite enough to rush to the opposite extreme, though the experience of the war showed that a fairly strict rationing on scientific lines is already a possibility. But every month we are approaching nearer to a knowledge of the dietaries best suited for any individual case, a knowledge which will be as efficient as the instinct of the insect, and infinitely more elastic.