The dish of my inventing does not incite dislike: far from it. The grubs attack it without hesitation and consume it with every appearance of the usual appetite. Things could not go better if the food had not been altered by my culinary recipes. Everything goes down, including the morsels in which I feared that I had overdone the addition of albumen. And—an even more important point—the Osmia-larvae fed in this manner attain their normal dimensions and spin their cocoons, from which adult insects issue in the following year. Notwithstanding the albuminous regimen, the cycle of the evolution is achieved without impediment.
What are we to conclude from all this? I feel greatly embarrassed. Omne vivum ex ovo, the physiologists tell us. Every animal is carnivorous, in its first beginnings: it is formed and nourished at the cost of its egg, in which albumen predominates. The highest, the mammal, adheres to this diet for a long time: it has its mother's milk, rich in casein, another isomer of albumen. The gramnivorous nestling is first fed on grubs, which are better adapted to the niceties of its stomach; many of the minutest new-born creatures, being at once left to their own devices, take to animal food. In this way the original method of nourishment is continued for all alike: the method which allows flesh to be made from flesh and blood from blood, with no chemical process beyond the simplest modification. At maturity, when the stomach has acquired its full strength, vegetable food is adopted, involving a more complicated chemistry but easier to obtain. Milk is followed by fodder, worms by seeds, the prey in the burrow by the nectar of the flowers.
This supplies a partial explanation of the twofold diet of the Hymenoptera with carnivorous larvae: meat first, honey next. But then the note of interrogation is shifted. It stood elsewhere; it now stands here. Why is the Osmia, who as a larva fares so well on albumen, fed on honey at the start? Why do the Bee-tribe receive a vegetable diet when the other members of the order receive an animal diet?
If I were a believer in evolution, I should say yes, by the fact of its germ, every animal is originally carnivorous. The insect in particular starts with albuminoid materials. Many larvae adhere to the egg-food, many adult insects do likewise. But the struggle to fill the belly, which after all is the struggle for life, demands something better than the precarious hazards of the chase. Man, at first a ravenous hunter after game, brought the flock into existence and turned shepherd to avoid a time of dearth. An even greater progress inspired him to scrape the earth and to sow seed, which assures him of a living. The evolution from scarcity to moderation and from moderation to plenty has led to the resources of husbandry.
The animals forestalled us this path of progress. The ancestors of the Philanthus, in the remote ages of the lacustrian tertiary formations, lived by prey in both the larval and the adult forms: they hunted for themselves as well as for the family. They did not confine themselves to emptying the Bee's crop, as their descendants do to this day: they devoured the deceased. From the beginning to the end they remained flesh-eaters. Later, fortunate innovators, whose race supplanted the laggards, discovered an inexhaustible nourishment, obtained without dangerous conflicts or laborious search: the sugary secretions of the flowers. The costly habit of living on prey, which does not favour large populations, was maintained for the feeble larvae; but the vigorous adult broke herself of it to lead an easier and more prosperous life. Thus, gradually, was formed the Philanthus of our day; thus was acquired the twofold diet of the various predatory insects our contemporaries.
The Bee has done better still: from the moment of leaving the egg she delivered herself completely from food-stuffs the acquisition of which depended on chance. She discovered honey, the grubs' food. Renouncing the chase for ever and becoming an agriculturalist pure and simple, the insect attains a degree of physical and moral prosperity which the predatory species are far from sharing. Hence the flourishing colonies of the Anthophorae, the Osmiae, the Eucerae (A genus of long-horned Burrowing Bees.—Translator's Note.), the Halicti and other honey-manufacturers, whereas the predatory insects work in isolation; hence the societies in which the Bee displays her wonderful tendencies, the supreme expression of instinct.
This is what I should say if I belonged to that school. It all forms a chain of very logical deductions and proffers itself with a certain air of likelihood which we should be glad to find in a host of evolutionist arguments put forward as irrefutable. Well, I will make a present of my deductive views, without regret, to whoever cares to have them: I don't believe one word of them; and I confess my profound ignorance of the origin of the twofold diet.
What I do understand more clearly, after all these investigations, is the tactics of the Philanthus. When witnessing her ferocious feasting, the real reason of which was unknown to me, I heaped the most ill-sounding epithets upon her, calling her a murderess, a bandit, a pirate, a robber of the dead. Ignorance is always evil-tongued; the man who does not know indulges in rude assertions and mischievous interpretations. Now that my eyes have been opened to the facts, I hasten to apologize and to restore the Philanthus to her place in my esteem. In draining the crops of her Bees the mother is performing the most praiseworthy of all actions: she is protecting her family against poison. If she happens to kill on her own account and to abandon the corpse after making it disgorge, I dare not reckon this against her as a crime. When the habit has been formed of emptying the Bee's crop with a good motive, there is a great temptation to do it again with no other excuse than hunger. Besides, who knows? Perhaps there is always at the back of her hunting some thought of game which might be useful for the larvae. Although not carried into effect, the intention excuses the deed.
I therefore withdraw my epithets in order to admire the insect's maternal logic and to hold it up to the admiration of others. The honey would be pernicious to the health of the larvae. How does the mother know that the syrup, a treat for her, is unwholesome for her young? To this question our science offers no reply. The honey, I say, would imperil the grubs' lives, The Bee must therefore first be made to disgorge. The disgorging must be effected without lacerating the victim, which the nurseling must receive in the fresh state; and the operation is impracticable on a paralysed insect because of the resistance of the stomach. The Bee must therefore be killed outright instead of being paralysed, or the honey will not be voided. Instantaneous death can be inflicted only by wounding the primordial centre of life. The sting must therefore aim at the cervical ganglia, the seat of innervation on which the rest of the organism depends. To reach them there is only one way, through the little gap in the throat. It is here therefore that the sting must be inserted; and it is here in fact that it is inserted, in a spot hardly as large as the twenty-fifth of an inch square. Suppress a single link of this compact chain, and the Bee-fed Philanthus becomes impossible.
That honey is fatal to carnivorous larvae is a fact which teems with consequences. Several Hunting Wasps feed their families upon Bees. These include, to my knowledge, the Crowned Philanthus (P. coronatus, FAB.), who lines her burrows with big Halicti; the Robber Philanthus (P. raptor, LEP.), who chases all the smaller-sized Halicti, suited to her own dimensions, indifferently; the Ornate Cerceris (C. ornata, FAB.), another passionate lover of Halicti; and the Palarus (P. flavipes, FAB.), who, with a curious eclecticism, stacks in her cells the greater part of the Hymenopteron clan that does not exceed her powers. What do these four huntresses and the others of similar habits do with their victims whose crops are more or less swollen with honey? They must follow the example of the Bee-eating Philanthus and make them disgorge, lest their family perish of a honeyed diet; they must manipulate the dead Bee, squeeze her and drain her dry. Everything goes to show it. I leave it to the future to display these dazzling proofs of my doctrine in their proper light.