What has occurred? The larva has opened a temporary breach in the wall of its shell; and through this orifice, in which a slight thickness of the outer glaze still remains, it has expelled the excess of mortar which it could not employ within. This practice of forming oubliettes in the shell of its prison does not endanger the grub, as they are immediately closed, and hermetically sealed by the base of the jet, which is compressed as by a stroke of a trowel. The stopper is so quickly put in place that the contents remain moist in spite of the frequent breaches made in the shell of the "pear." There is no danger of an influx of the dry outer air.
The Sisyphus seems to be aware of the peril which later on, in the dog-days, will threaten its "pear," small as it is, and so near the surface of the ground. It is extremely precocious. It labours in April and May when the air is mild. In the first fortnight of July, before the terrible dog-days have arrived, the members of its family break their shells and set forth in search of the heap of droppings which will furnish them with food and lodging during the fierce days of summer. Then come the short but pleasant days of autumn, the retreat underground and the winter torpor, the awakening of spring, and finally the cycle is closed by the festival of pellet-making.
One word more as to the fertility of the Sisyphus. My six couples under the wire-gauze cover furnished me with fifty-seven inhabited pellets. This gives an average of more than nine to each couple; a figure which the Scarabæus sacer is far from attaining. To what should we attribute this superior fertility? I can only see one cause: the fact that the male works as valiantly as the female. Family cares too great for the strength of one are not too heavy when there are two to support them.
CHAPTER XIII
A BEE-HUNTER: THE PHILANTHUS AVIPORUS
To encounter among the Hymenoptera, those ardent lovers of flowers, a species which goes a-hunting on its own account is, to say the least of it, astonishing. That the larder of the larvæ should be provisioned with captured prey is natural enough; but that the provider, whose diet is honey, should itself devour its captives is a fact both unexpected and difficult to comprehend. We are surprised that a drinker of nectar should become a drinker of blood. But our surprise abates if we consider the matter closely. The double diet is more apparent than real; the stomach which fills itself with the nectar of flowers does not gorge itself with flesh. When she perforates the rump of her victim the Odynerus does not touch the flesh, which is a diet absolutely contrary to her tastes; she confines herself to drinking the defensive liquid which the grub distils at the end of its intestine. For her this liquid is doubtless a beverage of delicious flavour, with which she relieves from time to time her staple diet of the honey distilled by flowers, some highly spiced condiment, appetiser or aperient, or perhaps—who knows?—a substitute for honey. Although the qualities of the liquid escape me, I see at least that Odynerus cares nothing for the rest. Once the pouch is emptied the larva is abandoned as useless offal, a certain sign of non-carnivorous appetites. Under these conditions the persecutor of Chrysomela can no longer be regarded as guilty of an unnatural double dietary.
We may even wonder whether other species also are not apt to draw some direct profit from the hunting imposed upon them by the needs of the family. The procedure of Odynerus in opening the anal pouch is so far removed from the usual that we should not anticipate many imitators; it is a secondary detail, and impracticable with game of a different kind. But there may well be a certain amount of variety in the means of direct utilisation. Why, for example, when the victim which has just been paralysed or rendered insensible by stinging contains in the stomach a delicious meal, semi-liquid or liquid in consistency, should the hunter scruple to rob the half-living body and force it to disgorge without injuring the quality of its flesh? There may well be robbers of the moribund, attracted not by their flesh but by the appetising contents of their stomachs.
As a matter of fact there are such, and they are numerous. In the first rank we may cite that hunter of the domestic bee, Philanthus aviporus (Latreille). For a long time I suspected Philanthus of committing such acts of brigandage for her own benefit, having many times surprised her gluttonously licking the honey-smeared mouth of the bee; I suspected that her hunting of the bee was not undertaken entirely for the benefit of her larvæ. The suspicion was worth experimental confirmation. At the time I was interested in another question also: I wanted to study, absolutely at leisure, the methods by which the various predatory species dealt with their victims. In the case of Philanthus I made use of the improvised cage already described; and Philanthus it was who furnished me with my first data on the subject. She responded to my hopes with such energy that I thought myself in possession of an unequalled method of observation, by means of which I could witness again and again, to satiety even, incidents of a kind so difficult to surprise in a state of nature. Alas! the early days of my acquaintance with Philanthus promised me more than the future had in store for me! Not to anticipate, however, let us place under the bell-glass the hunter and the game. I recommend the experiment to whomsoever would witness the perfection with which the predatory Hymenoptera use their stings. The result is not in doubt and the waiting is short; the moment the prey is perceived in an attitude favourable to her designs, the bandit rushes at it, and all is over. In detail, the tragedy develops as follows:
I place under a bell-glass a Philanthus and two or three domestic bees. The prisoners climb the glass walls, on the more strongly lighted side; they ascend, descend, and seek to escape; the polished, vertical surface is for them quite easy to walk upon. They presently quiet down, and the brigand begins to notice her surroundings. The antennæ point forward, seeking information; the hinder legs are drawn up with a slight trembling, as of greed and rapacity, in the thighs; the head turns to the right and the left, and follows the evolutions of the bees against the glass. The posture of the scoundrelly insect is strikingly expressive; one reads in it the brutal desires of a creature in ambush, the cunning patience that postpones attack. The choice is made, and Philanthus throws herself upon her victim.