ATIONING ACCORDING TO SEX

More Hunting Wasps by Jean-Henri Fabre, is part of the HackerNoon Books Series. You can jump to any chapter in this book here. ATIONING ACCORDING TO SEX

CHAPTER 9. RATIONING ACCORDING TO SEX.

Considered in respect of quality, the food has just disclosed our profound ignorance of the origins of instinct. Success falls to the blusterers, to the imperturbable dogmatists, from whom anything is accepted if only they make a little noise. Let us discard this bad habit and admit that really, if we go to the bottom of things, we know nothing about anything. Scientifically speaking, nature is a riddle to which human curiosity finds no definite solution. Hypothesis follows hypothesis; the theoretical rubbish-heap grows bigger and bigger; and still truth escapes us. To know how to know nothing might well be the last word of wisdom.

Considered in respect of quantity, the food sets us other problems, no less obscure. Those of us who devote ourselves assiduously to studying the customs of the game-hunting Wasps soon find our attention arrested by a very remarkable fact, at the time when our mind, refusing to be satisfied with sweeping generalities, which our indolence too readily makes shift with, seeks to enter as far as possible into the secret of the details, so curious and sometimes so important, as and when they become better-known to us. This fact, which has preoccupied me for many a long year, is the variable quantity of the provisions packed into the burrow as food for the larva.

Each species is scrupulously faithful to the diet of its ancestors. For more than a quarter of a century I have been exploring my district; and I have never known the diet to vary. To-day, as thirty years ago, each huntress must have the game which I first saw her pursuing. But, though the nature of the victuals is constant, the quantity is not so. In this respect the difference is so great that he would need to be a very superficial observer who should fail to perceive it on his first examination of the burrows. In the beginning, this difference, involving two, three, four times the quantity and more, perplexed me extremely and led me to the conclusions which I reject to-day.

Here, among the instances most familiar to me, are some examples of these variations in the number of victims provided for the larva, victims, of course, very nearly identical in size. In the larder of the Yellow-winged Sphex, after the victualling is completed and the house shut up, two or three Crickets are sometimes found and sometimes four. Stizus ruficornis (Cf. "The Hunting Wasps": chapter 20; also "Bramble-bees and Others": chapter 9.—Translator's Note.), established in some vein of soft sandstone, places three Praying Mantes in one cell and five in another. Of the caskets fashioned by Amedeus' Eumenes (Cf. "The Mason-wasps": chapter 1.—Translator's Note.) out of clay and bits of stone, the more richly endowed contain ten small caterpillars, the more poorly furnished five. The Sand Cerceris (Cf. "The Hunting Wasps": chapter 2.—Translator's Note.) will sometimes provide a ration of eight Weevils and sometimes one of twelve or even more. My notes abound in abstracts of this kind. It is unnecessary for the purpose in hand to quote them all. It will serve our object better if I give the detailed inventory of the Bee-eating Philanthus and of the Mantis-hunting Tachytes, considered especially with regard to the quantity of the victuals.

The slayer of Hive-bees is frequently in my neighbourhood; and I can obtain from her with the least trouble the greatest number of data. In September I see the bold filibuster flying from clump to clump of the pink heather pillaged by the Bee. The bandit suddenly arrives, hovers, makes her choice and swoops down. The trick is done: the poor worker, with her tongue lolling from her mouth in the death-struggle, is carried through the air to the underground den, which is often a very long way from the spot of the capture. The trickling of earthy refuse, on the bare banks, or on the slopes of footpaths, instantly reveals the dwellings of the ravisher; and, as the Philanthus always works in fairly populous colonies, I am able, by noting the position of the communities, to make sure of fruitful excavations during the forced inactivity of winter.

The sapping is a laborious task, for the galleries run to a great depth. Favier wields the pick and spade; I break the clods which he brings down and open the cells, whose contents—cocoons and remnants of provisions—I at once pour into a little screw of paper. Sometimes, when the larva is not developed, the stack of Bees is intact; more often the victuals have been consumed; but it is always possible to tell the number of items provided. The heads, abdomens and thoraxes, emptied of their fleshy substance and reduced to the tough outer skin, are easily counted. If the larva has chewed these overmuch, the wings at least are left; these are sapless organs which the Philanthus absolutely scorns. They are likewise spared by moisture, putrefaction and time, so much so that it is no more difficult to take an inventory of a cell several years old than one of a recent cell. The essential thing is not to overlook any of these tiny relics while placing them in the paper bag, amid the thousand incidents of the excavation. The rest of the work will be done in the study, with the aid of the lens, taking the remains heap by heap; the wings will be separated from the surrounding refuse and counted in sets of four. The result will give the amount of the provisions. I do not recommend this task to any one who is not endowed with a good stock of patience, nor above all to any one who does not start with the conviction that results of great interest are compatible with very modest means.

My inspection covers a total of one hundred and thirty-six cells, which are divided as in the table below:

2 cells each containing 1 Bee

52 cells each containing 2 Bees

36 cells each containing 3 Bees

36 cells each containing 4 Bees

9 cells each containing 5 Bees

1 cell containing 6 Bees

—-

136

The Mantis-hunting Tachytes consumes its heap of Mantes, the horny envelope included, without leaving any remains but scanty crumbs, quite insufficient to establish the number of items provided. After the meal is completed, any inventory of the rations becomes impossible. I therefore have recourse to the cells which still contain the egg or the very young larva and, above all, to those whose provisions have been invaded by a tiny parasitic Gnat, a Tachina (Cf. "The Hunting Wasps": chapters 4 and 16.—Translator's Note.), which drains the game without cutting it up and leaves the whole skin intact. Twenty-five larders, put to the count, give me the following result:

8 cells each containing 3 items

5 cells each containing 4 items

4 cells each containing 6 items

3 cells each containing 7 items

2 cells each containing 8 items

1 cell containing 9 items

1 cell containing 12 items

1 cell containing 16 items

—-

25

The predominant game is the Praying Mantis, green; next comes the Grey Mantis, ash-coloured. A few Empusae make up the total. The specimens vary in dimensions within fairly elastic limits: I measure some which are a third to a half inch long, averaging two-thirds to one inch long, and some which are two-fifths, averaging three quarters. I see pretty plainly that their number increases in proportion as their size diminishes, as though the Tachytes were seeking to make up for the smallness of the game by increasing the amount; none the less I find it quite impossible to detect the least equivalence by combining the two factors of number and size. If the huntress really estimates the provisions, she does so very roughly; her household accounts are not at all well kept; each head of game, large or small, must always count as one in her eyes.

Put on my guard, I look to see whether the honey-gathering Bees have a double service, like the game-hunting Wasps'. I estimate the amount of honeyed paste; I gauge the cups intended to contain it. In many cases the result resembles the first obtained: the abundance of provisions varies from one cell to another. Certain Osmiae (O. cornuta and O. tricornis (Cf. "Bramble-bees and Others": passim; and, in particular, chapters 3 to 5.—Translator's Note.)) feed their larvae on a heap of pollen-dust moistened in the middle with a very little disgorged honey. One of these heaps may be three or four times the size of some other in the same group of cells. If I detach from its pebble the nest of the Mason-bee, the Chalicodoma of the Walls, I see cells of large capacity, sumptuously provisioned; close beside these I see others, of less capacity, with victuals parsimoniously allotted. The fact is general; and it is right that we should ask ourselves the reason for these marked differences in the relative quantity of foodstuffs and for these unequal rations.

I at last began to suspect that this is first and foremost a question of sex. In many Bees and Wasps, indeed, the male and the female differ not only in certain details of internal or external structure—a point of view which does not affect the present problem—but also in length and bulk, which depend in a high degree on the quantity of food.

Let us consider in particular the Bee-eating Philanthus. Compared with the female, the male is a mere abortion. I find that he is only a third to half the size of the other sex, as far as I can judge by sight alone. To obtain exactly the respective quantities of substance, I should need delicate balances, capable of weighing down to a milligramme. My clumsy villager's scales, on which potatoes may be weighed to within a kilogramme or so, do not permit of this precision. I must therefore rely on the evidence of my sight alone, evidence, for that matter, which is amply sufficient in the present instance. Compared with his mate, the Mantis-hunting Tachytes is likewise a pigmy. We are quite astonished to see him pestering his giantess on the threshold of the burrows.

We observe differences no less pronounced of size—and consequently of volume, mass and weight—in the two sexes of many Osmiae. The differences are less emphatic, but are still on the same side, in the Cerceres, the Stizi, the Spheges, the Chalicodomae and many more. It is therefore the rule that the male is smaller than the female. There are of course some exceptions, though not many; and I am far from denying them. I will mention certain Anthidia where the male is the larger of the two. Nevertheless, in the great majority of cases the female has the advantage.

And this is as it should be. It is the mother, the mother alone, who laboriously digs underground galleries and chambers, kneads the plaster for coating the cells, builds the dwelling-house of cement and bits of grit, bores the wood and divides the burrow into storeys, cuts the disks of leaf which will be joined together to form honey-pots, works up the resin gathered in drops from the wounds in the pine-trees to build ceilings in the empty spiral of a Snail-shell, hunts the prey, paralyses it and drags it indoors, gathers the pollen-dust, prepares the honey in her crop, stores and mixes the paste. This severe labour, so imperious and so active, in which the insect's whole life is spent, manifestly demands a bodily strength which would be quite useless to the male, the amorous trifler. Thus, as a general rule, in the insects which carry on an industry the female is the stronger sex.

Does this pre-eminence imply more abundant provisions during the larval stage, when the insect is acquiring the physical growth which it will not exceed in its future development? Simple reflection supplies the answer: yes, the aggregate growth has its equivalent in the aggregate provisions. Though so slight a creature as the male Philanthus finds a ration of two Bees sufficient for his needs, the female, twice or thrice as bulky, will consume three to six at least. If the male Tachytes requires three Mantes, his consort's meal will demand a batch of something like ten. With her comparative corpulence, the female Osmia will need a heap of paste twice or thrice as great as that of her brother, the male. All this is obvious; the animal cannot make much out of little.

Despite this evidence, I was anxious to enquire whether the reality corresponded with the previsions of the most elementary logic. Instances are not unknown in which the most sagacious deductions have been found to disagree with the facts. During the last few years, therefore, I have profited by my winter leisure to collect, from spots noted as favourable during the working-season, a few handfuls of cocoons of various Digger-wasps, notably of the Bee-eating Philanthus, who has just furnished us with an inventory of provisions. Surrounding these cocoons and thrust against the wall of the cell were the remnants of the victuals—wings, corselets, heads, wing-cases—a count of which enabled me to determine how many head of game had been provided for the larva, now enclosed in its silken abode. I thus obtained the correct list of provisions for each of the huntress' cocoons. On the other hand, I estimated the quantities of honey, or rather I gauged the receptacles, the cells, whose capacity is proportionate to the mass of the provisions stored. After making these preparations, registering the cells, cocoons and rations and putting all my figures in order, I had only to wait for the hatching-season to determine the sex.

Well, I found that logic and experiment were in perfect agreement. The Philanthus-cocoons with two Bees gave me males, always males; those with a larger ration gave me females. From the Tachytes-cocoons with double or treble that ration I obtained females. When fed upon four or five Nut-weevils, the Sand Cerceris was a male; when fed upon eight or ten, a female. In short, abundant provisions and spacious cells yield females; scanty provisions and narrow cells yield males. This is a law upon which I may henceforth rely.

At the stage which we have now reached a question arises, a question of major importance, touching the most nebulous aspect of embryogeny. How is it that the larva of the Philanthus, to take a particular case, receives three to five Bees from its mother when it is to become a female and not more than two when it is to become a male? Here the various head of game are identical in size, in flavour, in nutritive properties. The food-value is precisely in proportion to the number of items supplied, a helpful detail which eliminates the uncertainties wherein we might be left by the provision of game of different species and varying sizes. How is it, then, that a host of Bees and Wasps, of honey-gatherers as well as huntresses, store a larger or smaller quantity of victuals in their cells according as the nurselings are to become females or males?

The provisions are stored before the eggs are laid; and these provisions are measured by the needs of the sex of an egg still inside the mother's body. If the egg-laying were to precede the rationing, which occasionally takes place, as with the Odyneri (Cf. "The Hunting Wasps": chapters 2 and 8.—Translator's Note.), for example, we might imagine that the gravid mother enquires into the sex of the egg, recognizes it and stacks victuals accordingly. But, whether destined to become a male or a female, the egg is always the same; the differences—and I have no doubt that there are differences—are in the domain of the infinitely subtle, the mysterious, imperceptible even to the most practised embryogenist. What can a poor insect see—in the absolute darkness of its burrow, moreover—where science armed with optical instruments has not yet succeeded in seeing anything? And besides, even were it more discerning than we are in these genetic obscurities, its visual discernment would have nothing whereupon to practice. As I have said, the egg is laid only when the corresponding provisions are stored. The meal is prepared before the larva which is to eat it has come into the world. The supply is generously calculated by the needs of the coming creature; the dining-room is built large or small to contain a giant or a dwarf still germinating in the ovarian ducts. The mother, therefore, knows the sex of her egg beforehand.

A strange conclusion, which plays havoc with our current notions! The logic of the facts leads us to it directly. And yet it seems so absurd that, before accepting it, we seek to escape the predicament by another absurdity. We wonder whether the quantity of food may not decide the fate of the egg, originally sexless. Given more food and more room, the egg would become a female; given less food and less room, it would become a male. The mother, obeying her instincts, would store more food in this case and less in that; she would build now a large and now a small cell; and the future of the egg would be determined by the conditions of food and shelter.

Let us make every test, every experiment, down to the absurd: the crude absurdity of the moment has sometimes proved to be the truth of the morrow. Besides, the well-known story of the Hive-bee should make us wary of rejecting paradoxical suppositions. Is it not by increasing the size of the cell, by modifying the quality and quantity of the food, that the population of a hive transforms a worker larva into a female or royal larva? It is true that the sex remains the same, since the workers are only incompletely developed females. The change is none the less miraculous, so much so that it is almost lawful to enquire whether the transformation may not go further, turning a male, that poor abortion, into a sturdy female by means of a plentiful diet. Let us therefore resort to experiment.

I have at hand some long bits of reed in the hollow of which an Osmia, the Three-horned Osmia, has stacked her cells, bounded by earthen partitions. I have related elsewhere (Cf. "Bramble-bees and Others": chapters 2 to 5.—Translator's Note.) how I obtain as many of these nests as I could wish for. When the reed is split lengthwise, the cells come into view, together with their provisions, the egg lying on the paste, or even the budding larva. Observations multiplied ad nauseam have taught me where to find the males and where the females in this apiary. The males occupy the fore-part of the reed, the end next to the opening; the females are at the bottom, next to the knot which serves as a natural stopper to the channel. For the rest, the quantity of the provisions in itself points to the sex: for the females it is twice or thrice as great as for the males.

In the scantily-provided cells, I double or treble the ration with food taken from other cells; in the cells which are plentifully supplied, I reduce the portion to a half or a third. Controls are left: that is to say, some cells remain untouched, with their provisions as I found them, both in the part which is abundantly provided and in that which is more meagrely rationed. The two halves of the reed are then restored to their original position and firmly bound with a few turns of wire. We shall see, when the time comes, whether these changes increasing or decreasing the victuals have determined the sex.

Here is the result: the cells which at first were sparingly provided, but whose supplies were doubled or trebled by my artifice, contain males, as foretold by the original amount of victuals. The surplus which I added has not completely disappeared, far from it: the larva has had more than it needed for its evolution as a male; and, being unable to consume the whole of its copious provisions, it has spun its cocoon in the midst of the remaining pollen-dust. These males, so richly supplied, are of handsome but not exaggerated proportions; you can see that the additional food has profited them to some small extent.

The cells with abundant provisions, reduced to a half or a third by my intervention, contain cocoons as small as the male cocoons, pale, translucent and limp, whereas the normal cocoons are dark-brown, opaque and firm to the touch. These, we perceive at once, are the work of starved, anaemic weavers, who, failing to satisfy their appetite and having eaten the last grain of pollen, have, before dying, done their best with their poor little drop of silk. Those cocoons which correspond with the smallest allowance of food contain only a dead and shrivelled larva; others, in whose case the provisions were less markedly decreased, contain females in the adult form, but of very diminutive size, comparable with that of the males, or even smaller. As for the controls which I was careful to leave, they confirm the fact that I had males in the part near the orifice of the reed and females in the part near the knot closing the channel.

Is this enough to dispose of the very improbable supposition that the determination of the sex depends on the quantity of food? Strictly speaking, there is still one door open to doubt. It may be said that experiment, with its artifices, does not succeed in realizing the delicate natural conditions. To make short work of all objections, I cannot do better than have recourse to facts in which the experimenter's hand has not intervened. The parasites will supply us with these facts; they will show us how alien the quantity and even the quality of the food are from either specific or sexual characters. The subject of enquiry thus becomes double, instead of single as it was when I plundered one cell in my split reeds to enrich another. Let us follow this double current for a little while.

An Ammophila, the Silky Ammophila (Cf. "The Hunting Wasps": chapter 13.—Translator's Note.), which feeds on Looper caterpillars (Known also as Measuring-worms, Inchworms, Spanworms and Surveyors: the caterpillars of the Geometrid Moths.—Translator's Note.), has just been reared in my refectory on Spiders. Replete to the regulation point, it spins its cocoon. What will emerge from this? If the reader expects to see any modifications, caused by a diet which the species, left to itself, had never effected, let him be undeceived and that quickly. The Ammophila fed on Spiders is precisely the same as the Ammophila fed on caterpillars, just as man fed on rice is the same as man fed on wheat. In vain I pass my lens over the product of my art: I cannot distinguish it from the natural product; and I defy the most meticulous entomologist to perceive any difference between the two. It is the same with my other boarders who have had their diet altered.

I see the objection coming. The differences may be inappreciable, for my experiments touch only a first rung of the ladder. What would happen if the ladder were prolonged, if the offspring of the Ammophila fed on Spiders were given the same food generation after generation? These differences, at first imperceptible, might become accentuated until they grew into distinct specific characters; the habits and instincts might also change; and in the end the caterpillar-huntress might become a Spider-huntress, with a shape of her own. A species would be created, for, among the factors at work in the transformation of animals, the most important of all is incontestably the type of food, the nature of the thing wherewith the animal builds itself. All this is much more important than the trivialities which Darwin relies upon.

To create a species is magnificent in theory, so that we find ourselves regretting that the experimenter is not able to continue the attempt. But, once the Ammophila has flown out of the laboratory to slake her thirst at the flowers in the neighbourhood, just to try to find her again and induce her to entrust you with her eggs, which you would rear in the refectory, to increase the taste for Spiders from generation to generation! Merely to dream of it were madness. Shall we, in our helplessness, admit ourselves beaten by the evolutionary effects of diet? Not a bit of it! One experiment—and you could not wish for a more decisive—is continually in progress, apart from all artifices, on an enormous scale. It is brought to our notice by the parasites.

They must, we are told, have acquired the habit of living on others in order to save themselves work and to lead an easier life. The poor wretches have made a sorry blunder. Their life is of the hardest. If a few establish themselves comfortably, dearth and dire famine await most of the rest. There are some—look at certain of the Oil-beetles—exposed to so many chances of destruction that, to save one, they are obliged to procreate a thousand. They seldom enjoy a free meal. Some stray into the houses of hosts whose victuals do not suit them; others find only a ration quite insufficient for their needs; others—and these are very numerous—find nothing at all. What misadventures, what disappointments do these needy creatures suffer, unaccustomed as they are to work! Let me relate some of their misfortunes, gleaned at random.

The Girdled Dioxys (D. cincta) loves the ample honey-stores of the Chalicodoma of the Pebbles. There she finds abundant food, so abundant that she cannot eat it all. I have already passed censure on this waste. (Cf. "The Mason-bees": chapter 10.—Translator's Note.) Now a little Osmia (O. cyanoxantha, Perez) makes her nest in the Mason's deserted cells; and this Bee, a victim of her ill-omened dwelling, also harbours the Dioxys. This is a manifest error on the parasite's part. The nest of the Chalicodoma, the hemisphere of mortar on its pebble, is what she is looking for, to confide her eggs to it. But the nest is now occupied by a stranger, by the Osmia, a circumstance unknown to the Dioxys, who comes stealing up to lay her egg in the mother's absence. The dome is familiar to her. She could not know it better if she had built it herself. Here she was born; here is what her family wants. Moreover, there is nothing to arouse her suspicions: the outside of the home has not changed its appearance in any respect; the stopper of gravel and green putty, which later will form a violent contrast with its white front, is not yet constructed. She goes in and sees a heap of honey. To her thinking this can be nothing but the Chalicodoma's portion. We ourselves would be beguiled, in the Osmia's absence. She lays her eggs in this deceptive cell.

Her mistake, which is easy to understand, does not in any way detract from her great talents as a parasite, but it is a serious matter for the future larva. The Osmia, in fact, in view of her small dimensions, collects but a very scanty store of food: a little loaf of pollen and honey, hardly the size of an average pea. Such a ration is insufficient for the Dioxys. I have described her as a waster of food when her larva is established, according to custom, in the cell of the Mason-bee. This description no longer applies; not in the very least. Inadvertently straying to the Osmia's table, the larva has no excuse for turning up its nose; it does not leave part of the food to go bad; it eats up the lot without having had enough.

This famine-stricken refectory can give us nothing but an abortion. As a matter of fact, the Dioxys subjected to this niggardly test does not die, for the parasite must have a tough constitution to enable it to face the disastrous hazards which lie in wait for it; but it attains barely half its ordinary dimensions, which means one-eighth of its normal bulk. To see it thus diminished, we are surprised at its tenacious vitality, which enables it to reach the adult form in spite of the extreme deficiency of food. Meanwhile, this adult is still the Dioxys; there is no change of any kind in her shape or colouring. Moreover, the two sexes are represented; this family of pigmies has its males and females. Dearth and the farinaceous mess in the Osmia's cell has had no more influence over species or sex than abundance and flowing honey in the Chalicodoma's home.

The same may be said of the Spotted Sapyga (S. punctata (A parasitic Wasp. Cf. "The Mason-bees": chapters 9 and 10.—Translator's Note.)), which, a parasite of the Three-pronged Osmia, a denizen of the bramble, and of the Golden Osmia, an occupant of empty Snail-shells, strays into the house of the Tiny Osmia (O. parvula (This bee makes her home in the brambles. Cf. "Bramble-dwellers and Others": chapters 2 and 3.—Translator's Note.)), where, for lack of sufficient food, it does not attain half its normal size.

A Leucopsis (Cf. "The Mason-bees": chapter 11.—Translator's Note.) inserts her eggs through the cement wall of our three Chalicodomae. I know her under two names. When she comes from the Chalicodoma of the Pebbles or Walls, whose opulent larva saturates her with food, she deserves by her large size the name of Leucopsis gigas, which Fabricius bestows upon her; when she comes from the Chalicodoma of the Sheds, she deserves no more than the name of L. grandis, which is all that Klug grants her. With a smaller ration "the giant" is to some degree diminished and becomes no more than "the large." When she comes from the Chalicodoma of the Shrubs, she is smaller still; and, if some nomenclator were to seek to describe her, she would no longer deserve to be called more than middling. From dimension 2 she has descended to dimension 1 without ceasing to be the same insect, despite the change of diet; and at the same time both sexes are present in the three nurselings, despite the variation in the quantity of victuals.

I obtain Anthrax sinuata ("The Mason-bees": chapters 8, 10 and 11.—Translator's Note.) from various bees' nests. When she issues from the cocoons of the Three-horned Osmia, especially the female cocoons, she attains the greatest development that I know of. When she issues from the cocoons of the Blue Osmia (O. cyanea, KIRB.), she is sometimes hardly one-third the length which the other Osmia gives her. And we still have the two sexes—that goes without saying—and still identically the same species.

Two Anthidia, working in resin, A. septemdentatum, LATR., and A. bellicosum, LEP. (For these Resin-bees, cf. "Bramble-bees and Others": chapter 10.—Translator's Note.), establish their domicile in old Snail-shells. The second harbours the Burnt Zonitis (Z. proeusta (Cf. "The Glow-worm and Other Beetles": chapter 6.—Translator's Note.)). Amply nourished this Meloe then acquires her normal size, the size in which she usually figures in the collections. A like prosperity awaits her when she usurps the provisions of Megachile sericans. (For this Bee, the Silky Leaf-cutter, cf. "Bramble-bees and Others": chapter 8.—Translator's Note.) But the imprudent creature sometimes allows itself to be carried away to the meagre table of the smallest of our Anthidia (A. scapulare, LATR. (A Cotton-bee, cf. idem: chapter 9.—Translator's Note.)), who makes her nests in dry bramble-stems. The scanty fare makes a wretched dwarf of the offspring belonging to either sex, without depriving them of any of their racial features. We still see the Burnt Zonitis, with the distinctive sign of the species: the singed patch at the tip of the wing-cases.

And the other Meloidae—Cantharides, Cerocomae, Mylabres (For these Blister-beetles or Oil-beetles, cf. "The Glow-worm and Other Beetles": chapter 6.—Translator's Note.)—to what inequalities of size are they not subject, irrespective of sex! There are some—and they are numerous—whose dimensions fall to a half, a third, a quarter of the regular dimensions. Among these dwarfs, these misbegotten ones, these victims of atrophy, there are females as well as males; and their smallness by no means cools their amorous ardour. These needy creatures, I repeat, have a hard life of it. Whence do they come, these diminutive Beetles, if not from dining-rooms insufficiently supplied for their needs? Their parasitical habits expose them to harsh vicissitudes. No matter: in dearth as well as in abundance the two sexes appear and the specific features remain unchanged.

It is unnecessary to linger longer over this subject. The demonstration is completed. The parasites tell us that changes in the quantity and quality of food do not lead to any transformation of species. Fed upon the larva of the Three-horned Osmia or of the Blue Osmia, Anthrax sinuata, whether of handsome proportions or a dwarf, is still Anthrax sinuata; fed upon the allowance of the Anthidium of the empty Snail-shells, the Anthidium of the brambles, the Megachile or doubtless many others, the Burnt Zonitis is still the Burnt Zonitis. Yet variation of diet ought to be a very potential factor in the problem of progress towards another form. Is not the world of living creatures ruled by the stomach? And the value of this factor is unity, changing nothing in the product.

The same parasites tell us—and this is the chief object of my digression—that excess or deficiency of nutriment does not determine the sex. So we are once more confronted with the strange proposition, which is now more positive than ever, that the insect which amasses provisions in proportion to the needs of the egg about to be laid knows beforehand what the sex of this egg will be. Perhaps the reality is even more paradoxical still. I shall return to the subject after discussing the Osmiae, who are very weighty witnesses in this grave affair. (Cf. "Bramble-bees and Others": chapters 3 to 5. The student is recommended to read these three chapters in conjunction with the present chapter, to which they form a sequel, with that on the Osmiae (chapter 2 of the above volume) intervening.—Translator's Note.)

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