Here is the home uncovered, in the bright light, under the sun’s rays. How will the [[316]]mother behave on her return? Let us consider the question in detail, according to scientific precepts: it is a perplexing position for the observer, as my recent experiences make me suspect. Here is the problem: the mother on arriving has the feeding of her larva as her object in view; but to reach this larva she must first find the door. The grub and the entrance-door: those are the two aspects of the question that appear to me to merit separate consideration. I therefore take away the grub, together with the provisions, and the end of the passage becomes a clear space. After making these preparations there is nothing to do but exercise patience.
The Wasp arrives at last and goes straight to where its door ought to be, that door of which naught but the threshold remains. Here, for more than an hour, I see her digging on the surface, sweeping, making the sand fly, and persisting, not in scooping out a new gallery, but in looking for that loose door which ought easily to give way before a mere push of the head and let the insect through. Instead of yielding materials, she finds firm soil, not yet disturbed. Warned by this resistance, she confines herself to exploring the surface, always in close proximity to the spot where the entrance should be. A few inches on either side is all that she allows [[317]]herself. The places which she has already tested and swept twenty times over she returns to test and sweep again, unable to bring herself to leave her narrow radius, so obstinate is her conviction that the door must be here and not elsewhere. Several times in succession I push her gently with a straw to some other point. She will not be put off: she returns straightway to the place where her door once stood. At rare intervals the gallery, now an open trench, seems to attract her attention, though very faintly. The Bembex takes a few steps towards it, still raking, and then goes back to the entrance. Twice or thrice I see her run the whole length of the conduit and reach the blind alley, the abode of her grub; here she gives a few careless strokes of the rake and hurries back to the spot where the entrance used to be, continuing her quest there with a persistency that ends by wearying mine. More than an hour has passed and the stubborn Wasp is still pursuing her search on the site of the vanished doorway.
What will happen when the larva is present? This is the next aspect of the question. To continue the experiment with the same Bembex would not have given me the positive evidence which I wanted, for the insect, rendered more obstinate by its vain quest, seemed to me now obsessed by a fixed idea, which would certainly [[318]]have obscured the facts which I wished to ascertain. I needed a fresh subject, one not over-excited and solely concerned with the impulses of the first moment. An opportunity soon presented itself.
I uncover the burrow from end to end as I have just explained, but without touching the contents: I leave the larva in its place, I respect the provisions; everything in the house is in order; there is nothing lacking but the roof. Well, in front of this open dwelling, of which the eye freely takes in every detail: entrance-hall, gallery, cell at the back with the grub and its heap of Flies; in front of this dwelling now a trench, at the end of which the larva wriggles under the blistering rays of the sun, the mother behaves exactly as her predecessor did. She alights at the point where the entrance used to be. It is here that she does her digging and sweeping; and it is here that she always returns after hurried visits elsewhere, within a radius of a few inches. There is no exploration of the tunnel, no anxiety about the tortured larva. The grub, whose delicate epidermis has just passed from the cool moisture of an underground cave to the fierce blaze of an untempered sun, is writhing on its heap of chewed Flies; the mother does not give it a thought. To her it is no more than any [[319]]other object lying on the sand: a little pebble, a pellet of earth, a scrap of dry mud, nothing more. It is unworthy of attention. This tender and faithful mother, who wears herself out in trying to reach her nurseling’s cradle, is wanting at the moment her entrance-door, the usual door and nothing but that door. What stirs her maternal heart is her yearning for the well-known passage. And yet the way is open: there is nothing to stop the mother; and the grub, the ultimate object of her anxiety, is tossing restlessly before her eyes. One bound would bring her to the side of the poor thing clamouring for assistance. Why does she not rush to her beloved nurseling? She could dig it a new dwelling and swiftly place it in safety underground. But no; the mother persists in seeking a passage that no longer exists, while her child is grilling in the sun before her eyes. My surprise is intense in the presence of this short-sighted mother, though the sense of motherhood is the most powerful and resourceful of all the feelings that stir the animal creation. I should hardly believe the evidence of my eyes but for experiments endlessly repeated with Cerceres and Philanthi as well as with Bembex of different species.
Here is something more remarkable still: the mother, after prolonged hesitation, at last [[320]]enters the roofless trench, all that remains of the original corridor. She goes forward, draws back, goes forward again, giving a few careless sweeps, here and there, without stopping. Guided by vague recollections and perhaps also by the smell of game emitted by the heap of Flies, she occasionally reaches the end of the gallery, the very spot at which the larva lies. Mother and son are now together. At this moment of meeting after long suffering, have we a display of eager solicitude, exuberant affection, any signs whatever of maternal joy? If you think so, you need only repeat my experiments to persuade yourself to the contrary. The Bembex does not recognize her larva at all; it is to her a worthless thing, something in her way, a nuisance. She walks over the grub, treads on it ruthlessly, as she hurries to and fro. When she wants to try and dig at the bottom of the cell, she thrusts it back with a brutal kick; she shoves it on one side, topples it over, flings it out as unceremoniously as if it were a big bit of gravel that hindered her in her work. Thus knocked about, the grub thinks of defending itself. I have seen it seize its mother by the tarsus with no more ceremony than it shows when it bites off the leg of its prey, the Fly. The struggle was hotly contested; but at last the fierce mandibles let go [[321]]and the mother vanished in terror, making a shrill whimpering noise with her wings. This unnatural sight of the son biting his mother and perhaps even trying to eat her is uncommon and is brought about by circumstances which the observer has not at his command; but what can always be witnessed is the Wasp’s profound indifference towards her offspring and the brutal contempt with which she treats that irksome lump of rubbish, the grub. Once she has raked out the end of the passage, which is the work of a moment, the Bembex returns to her favourite spot, the threshold, where she resumes her useless search. As for the grub, it continues to writhe and wriggle wherever its mother has kicked it. It will die without the mother’s coming to its assistance, for she fails to recognize it because she was unable to find the customary passage. Go back to-morrow and you shall see it lying in its trench, half baked by the sun and already a prey to the very Flies that were once its prey.
Such is the concatenation of instinctive actions, linked one to the other in an order which the gravest circumstances are powerless to disturb. What, after all, is the Bembex looking for? Her larva, obviously. But, to get at that larva, she must enter the burrow; and, to enter that burrow, she must first of all [[322]]find the door. And it is in the search for this door that the mother persists, despite the wide-open gallery, despite the provisions, despite the grub, all exposed to view. At the moment she cares not that her house is in ruins and her family in danger; what she wants above all things is the familiar passage, the passage through the loose sand. Perish everything, dwelling and inmate, if this passage be not found! Her actions are like a series of echoes each awakening the next in a settled order, which allows none to sound until the previous one has sounded. The first action could not be performed, not because of an obstacle, for the house is wide open, but for want of the usual entrance. That is enough: the subsequent actions shall not be performed; the first echo was dumb and all the rest are silent. What a gulf separates intelligence and instinct! Through the ruins of the demolished dwelling, a mother guided by intelligence hurries straight to her son; guided by instinct, she comes to a stubborn halt on the site of her old door. [[323]]
[1] For other essays on the homing of insects, cf. The Mason-bees: chaps. ii. to vi.—Translator’s Note. [↑]