Having done this and put the stolen prey safely away in a box, I yield my place to the Sphex, who has been on the watch beside me while I was rifling her home. Finding the door open, she goes in and stays for a few moments. Then she comes out and resumes her work where I interrupted it, that is to say, she starts conscientiously stopping the entrance to the cell by sweeping dust backwards and carrying grains of sand, which she continues to heap up with scrupulous care, as though she were doing useful work. When the door is once again thoroughly walled up, the insect brushes itself, seems to give a glance of satisfaction at the task accomplished, and finally flies away.
The Sphex must have known that the burrow contained nothing, because she went inside and even stayed there for some time; and yet, after this inspection of the pillaged abode, she [[185]]once more proceeds to close up the cell with the same care as though nothing out of the way had happened. Can she be proposing to use this burrow later, to return to it with a fresh victim and lay a new egg there? If so, her work of closing would be intended to prevent the access of intruders to the dwelling during her absence; it would be a measure of prudence against the attempts of other diggers who might covet the ready-made chamber; it might also be a wise precaution against internal dilapidations. And, as a matter of fact, some Hunting Wasps do take care to protect the entrance to the burrow by closing it temporarily, when the work has to be suspended for a time. Thus I have seen certain Ammophilæ, whose burrow is a perpendicular shaft, block the entrance to the home with a small flat stone when the insect goes off hunting or ceases its mining operations at sunset, the hour for striking work. But this is a slight affair, a mere slab laid over the mouth of the shaft. When the insect comes, it only takes a moment to remove the little flat stone; and the entrance is free.
On the other hand, the obstruction which we have just seen built by the Sphex is a solid barrier, a stout piece of masonry, where dust and gravel form alternate layers all the way down the passage. It is a definite performance [[186]]and not a provisional defence, as is proved by the care with which it is constructed. Besides, as I think I have shown pretty clearly, it is very doubtful, considering the way in which she acts, whether the Sphex will ever return to make use of the home which she has prepared. The next Ephippiger will be caught elsewhere; and the warehouse destined to receive her will be dug elsewhere too. But these, after all, are only arguments: let us rather have recourse to experiment, which is more conclusive here than logic.
I allowed nearly a week to elapse, in order to give the Sphex time to return to the burrow which she had so methodically closed and to make use of it for her next laying if such were her intention. Events corresponded with the logical inferences: the burrow was in the condition wherein I left it, still firmly closed, but without provisions, egg or larva. The proof was decisive: the Wasp had not been back.
So the plundered Sphex enters her house, makes a leisurely inspection of the empty chamber, and, a moment afterwards, behaves as though she had not perceived the disappearance of the bulky prey which but now filled the cell. Did she, in fact, fail to notice the absence of the provisions and the egg? Is she, who is so clear-sighted in her murderous proceedings, [[187]]dense enough not to realize that the cell is empty? I dare not accuse her of such stupidity. She is aware of it. But then why that other piece of stupidity which makes her close—and very conscientiously close—an empty burrow, one which she does not purpose to victual later? Here the work of closing is useless, is supremely absurd; no matter: the insect performs it with the same ardour as though the larva’s future depended on it. The insect’s various instinctive actions are then fatally linked together. Because one thing has been done, a second thing must inevitably be done to complete the first or to prepare the way for its completion; and the two acts depend so closely upon each other that the performing of the first entails that of the second, even when, owing to casual circumstances, the second has become not only inopportune but sometimes actually opposed to the insect’s interests. What object can the Sphex have in blocking up a burrow which has become useless, now that it no longer contains the victim and the egg, and which will always remain useless, since the insect will not return to it? The only way to explain this inconsequent action is to look upon it as the inevitable complement of the actions that went before. In the normal order of things, the [[188]]Sphex hunts down her prey, lays an egg and closes her burrow. The hunting has been done; the game, it is true, has been withdrawn by me from the cell; never mind: the hunting has been done, the egg has been laid; and now comes the business of closing up the home. This is what the insect does, without another thought, without in the least suspecting the futility of her present labours.
Experiment III
To know everything and to know nothing, according as it acts under normal or exceptional conditions: that is the strange antithesis presented by the insect race. Other examples, also drawn from the Sphex tribe, will confirm this conclusion. The White-edged Sphex (S. albisecta) attacks medium-sized Locusts, whereof the different species to be found in the neighbourhood of the burrow all furnish her with their tribute of victims. Because of the abundance of these Acridians, there is no need to go hunting far afield. When the burrow, which takes the form of a perpendicular shaft, is ready, the Sphex merely explores the purlieus of her lair, within a small radius, and is not long in finding some Locust browsing in the sunshine. To pounce upon her and sting her, [[189]]despite her kicking, is to the Sphex the matter of a moment. After some fluttering of its wings, which unfurl their carmine or azure fan, after some drowsy stretching of its legs, the victim ceases to move. It has now to be brought home, on foot. For this laborious operation the Sphex employs the same method as her kinswomen, that is to say, she drags her prize along between her legs, holding one of its antennæ in her mandibles. If she encounters some grassy jungle, she goes hopping and flitting from blade to blade, without ever letting slip her prey. When at last she comes within a few feet of her dwelling, she performs a manœuvre which is also practised by the Languedocian Sphex; but she does not attach as much importance to it, for she frequently neglects it. Leaving her captive on the road, the Wasp hurries home, though no apparent danger threatens her abode, and puts her head through the entrance several times, even going part of the way down the burrow. She next returns to the Locust and, after bringing her nearer the goal, leaves her a second time to revisit the burrow. This performance is repeated over and over again, always with the same anxious haste.
These visits are sometimes followed by grievous accidents. The victim, rashly abandoned [[190]]on hilly ground, rolls to the bottom of the slope; and the Sphex on her return, no longer finding it where she left it, is obliged to seek for it, sometimes fruitlessly. If she find it, she must renew a toilsome climb, which does not prevent her from once more abandoning her booty on the same unlucky declivity. Of these repeated visits to the mouth of the shaft, the first can be very logically explained. The Wasp, before arriving with her heavy burden, inquires whether the entrance to the home be really clear, whether nothing will hinder her from bringing in her game. But, once this first reconnaissance is made, what can be the use of the rest, following one after the other, at close intervals? Is the Sphex so volatile in her ideas that she forgets the visit which she has just paid and runs afresh to the burrow a moment later, only to forget this new inspection also and to start doing the same thing over and over again? That would be a memory with very fleeting recollections, whence the impression vanished almost as soon as it was produced. Let us not linger too long on this obscure point.
At last the game is brought to the brink of the shaft, with its antennæ hanging down the hole. We now again see, faithfully imitated, the method employed in the like case by the [[191]]Yellow-winged Sphex and also, but under less striking conditions, by the Languedocian Sphex. The Wasp enters alone, inspects the interior, reappears at the entrance, lays hold of the antennæ and drags the Locust down. While the Locust-huntress was making her examination of the home, I have pushed her prize a little farther back; and I obtained results similar in all respects to those which the Cricket-huntress gave me. Each Sphex displays the same obstinacy in diving down her burrow before dragging in the prey. Let us recall here that the Yellow-winged Sphex does not always allow herself to be caught by this trick of pulling away her Cricket. There are picked tribes, strong-minded families which, after a few disappointments, see through the experimenter’s wiles and know how to baffle them. But these revolutionaries, fit subjects for progress, are the minority; the remainder, mulish conservatives clinging to the old manners and customs, are the majority, the crowd. I am unable to say whether the Locust-huntress also varies in ingenuity according to the district which she hails from.