However it may be, the nests of termites, of bumblebees, of ants, and of most of the wasps are always established by royal couples which at the start must satisfy all the needs of the budding society. The need is great, but it quickly grows less, since there soon hatch young individuals of the same sex, which join their efforts to those of their parents. In Belonogaster, where communism is at its dawn, the young resemble the stem-mothers and have the same functions. Their ovaries are not yet ripe, and before becoming egg-layers they remain in the colony and act there as workers.
But the experiments of Marchai have shown that the sterility of the worker wasps is the result of functions which they perform in the society. Worn out with intense labor and giving much to the larvae, they are ordinarily incapable of forming eggs and have therefore subjected themselves to a nutritial castration. From that comes the very long retardation in the laying, which Ron-baud has observed with certain young females of Betono g aster, and from it also comes the peculiar constitution of the bumblebee societies, which are monogamous in our country and in which the workers are well-formed but sterile females, but which in America are polygamous, many females filling the role of egg-layers while others are true non-fertile workers. It is also a nutritial castration of the same origin to which we must attribute the existence of pure workers in the swarming colonies of Polybia and other polygamous wasps, the Meliponas and other true bees. With the latter and perhaps with other swarming species the nest is not established by the queen, but by the workers, which emigrate with her and do all the work except egg-laying.
In many cases, but not in all, the castration of the workers comes from insufficient larval food. This phenomenon is very evident with the insects whose nest is begun by the original couple or the original female. The first larva? are scantily fed because of the intensive work of the mother which has to provide for all needs. So the first-bom are always neuters or immature and are always of smaller size. But when the food of the larvae becomes more copious, when the young take a part in the work and set the founder free for her normal functions, then the size increases and there comes a moment when certain young develop into queens and males (royalties). This can easily be noted with the bumblebees and the wasps of our country. Termites do not seem to lend themselves to observation of this kind; however, with them also the castration is of alimentary origin, for their young larvae can be made royal when they are better nourished.
The influence of the nourishment of the larvae upon fecundity is much more evident still with the Meliponid of the genus Trigona and with the true bees generally, with the exception of Apis dorsata. These bees make their royal cells much more spacious than the others and provision them much more richly. With the Trigonas, where the cells are provisioned all at the same time and closed with the egg inside, the royal food seems to be of the same nature as that of the workers. With the bees whose larvae are nourished with the beak, this food is not only more copious but of a peculiar quality (royal jelly), and it is so effective that it is necessary for the bees to transform ordinary cells into royal cells for the use of the young larvae to which they will give the royal food in order to make of them future royalties.
These phenomena are much more obscure with the ants. According to the observations of Wheeler on the Ponerines, the nourishment is served by chance and it seems impossible to distinguish from the food alone between the worker larva? and the queen larvae ; but this is perhaps only apparently so, for there are other species in which the lack of nourishment makes the females retrograde into workers. It is thus, according to Wasmann, with the sanguinary ants, which take into their nests the Staphylynid parasites of the genus Lomechusa which they lick on account of the cutaneous secretion. Lameere says:
When these parasites become very numerous the ants become crowded. It is said that then the larvae which would have given birth to winged females, being badly cared for, produce only degenerate wingless females (pseudogynes) having transitional characters which brings them near the workers. This is the opposite of the transformation of a worker into a queen of the honeybee.
Before drawing any conclusion from the preceding facts, we must stop to consider two kinds of bees, namely the Meliponas and Apis dorsata, which differ from related forms in the mode of rearing their queens. Like the Trigonas, the Meliponas enclose their egg in a provisioned cell, but they do not build royal cells, and all are alike.
It is, then, not the nourishment which produces the differentiation of females into workers and queens with these forms. With Apis dorsata, as with all true bees, the larvae are nourished at the beak, but the queen larvae do not seem to receive a special food, and in any case are reared in the same cells as the workers. Here again the differentiation of the female individuals appears to be independent of the nourishment, and this differentiation is inherent in the protoplasm of the egg. This potential differentiation is still more evident in the eggs of termites whch produce soldiers armed with a frontal horn. Bonnier (1914) has shown, in fact, that the embryos of these soldiers already possess this horn and that the young leaves its egg-envelop with its definite characters. These facts are bothersome at first, since they seem to show that the female eggs of Melipona and of Apis dorsata and the soldier eggs of certain termites possess properties which are entirely lacking in the analogous case of other communistic insects. These last are called tropho-genic because they produce individuals whose sexual development depends on the food; the others are called blastogenic because they are already functionally differentiated.
But it seems difficult to admit that the female eggs of Apis dorsata and of the Meliponas and the eggs of the nasute soldiers of termites differ so profoundly from those of related forms. We believe it more rational to suppose that all eggs are more or less blastogenic,-that is to say capable of producing young of a determined kind,- but that this power is rarely so great as to resist the effects of a later feeding. With this very important restriction, we may apply to all communistic insects the explanation which Lameere applies only to the soldiers of the termites: "We find ourselves here in the presence of a phenomenon comparable to that which is offered to us by those Papilios which give in one egg-mass two or three varieties of females."
We need not delude ourselves, however, with this explanation, which is, rather, a comparison; it is far from clearing up a mystery which rests without doubt in the intimate constitution of the eggs and in the manner in which a female can make in her body eggs of different kinds other than of one sex. But the cause of this diversity is not, perhaps, so mysterious. Contrary to Lameere, who really followed the ideas of Weismann, we attribute it in part to properties acquired in the course of social evolution. Wheeler (1910) attributed the differentiation of castes in communistic societies to a philoprogenitive instinct which led the members of the colony to deprive themselves for their young and which already showed with the solitary ancestors of the social insects. We do not deny that that instinct might be necessary, just as a certain sociability is necessary, to the installation of the communistic life. But how has it been able to develop to the point of producing castes and of reacting on the constitution of the eggs! That is the gist of the problem.
But Belonogaster and Bombus have shown us that the castration of the females has been progressively brought about from the influence of work which will not allow the ovaries to become sufficiently nourished. This castration has resulted in the annihilation of the tendency to couple, to reduce the ovipositions or to make them disappear, and in addition to concentrate all the activity of the individual upon work,-that is to say to increase its philoprogenitive instincts. That such changes in the constitution of the reproductive glands and in the habits have been able to affect the somatic cells of the body and through them the eggs or germinative cells, is what we believe possible, in spite of the contrary assertions of Weismann (see page 154) ; and from this the habits and characters acquired by the neuters may be transmitted to the progeny by the means of males coming from non-fecundated eggs which usually produce workers.
To this Lamarckian explanation it cannot fail to be objected that worker eggs are rare and accidental, but they are much commoner than is believed, as the most recent investigations show, and many biologists think that with communistic insects they play an important role in the production of the males. In any case, it is enough that some egg-layings, even very scarce, should exist in order that the characters acquired by the neuters may be transmitted.
There is, then, reason to believe that the fertile female hands down to the neuters born to her, aside from mutation characters, those acquired progressively by their caste. What is not yet explained is the faculty of laying eggs of two kinds, some predestined to sexual functions and others to the life of neuters, but a mystery of the same kind exists concerning all females that have polymorphic progeny. We have seen, moreover, that this predestination is not absolute, and that with most communistic insects proper food and proper care can modify it.
The characters acquired by the royal individuals are a consequence of the specialization of the neuters. In so far as they take a more or less important part in the cares of the society, the royal individnals devote themselves more and more to sexual functions, and in the most perfect societies they know no others. Here again the characters and the habits are progressively acquired. With most social insects the royal individuals have preserved from their birth, and preserve sometimes all their lives, the characters of their solitary ancestors, especially the instruments of work which permit them to establish a new colony by themselves. Later, when their activity confines itself to the filling of the reproductive functions, they may become modified, and the females may acquire a considerable size in relation to the development of their ovaries. With the higher bees, Meliponas and true bees, the workers alone have to preserve the normal characters and the instruments for work. Exclusively occupied with egg-laying functions, the queens are extremely obese and do not possess these instruments. That they have lost them because of the specialization which belongs to them, is shown with the bumblebees, where the queens are not less well tooled than the female workers.