The site transformed four times over, the outworks of the abode changed in colour, scent, and material, the pain of a double wound,—all failed to disconcert the Hymenopteron or even to make her doubtful as to the precise locality of her doorway. I had exhausted my stratagems, and understood less than ever how the insect, if it have no special guide in some faculty unknown to us, can find its way when sight and smell are baffled by the artifices of which I have spoken. Some days later an experience gave me the opportunity to take up the problem from a new point of view. The Bembex burrow had to be bared in its whole extent, without quite destroying it, to which operation its shallowness and almost horizontal direction, and the light soil in which it was made, lent themselves readily. The sand was gradually scraped off with the blade of a knife, and thus, deprived of roof from end to end, the underground abode became a semi-canal or conduit, straight or curved, some eight inches long, open where was the entrance, and ending [[266]]in a cul-de-sac where lay the larva amid its food.
The dwelling was uncovered in full sunshine; how would the mother behave on her return? Let us consider the question scientifically. The observer may be greatly embarrassed: what I have already seen leads me to expect it. The mother’s impulse is to bring food to her larva, but to reach this larva she must first find the door. Grub and entrance are the points which appear to deserve being separately examined; therefore I take away grub and food, and the end of the passage is cleared. There is nothing more to do but arm one’s self with patience.
At last the Bembex arrives and makes straight for her absent door, only the threshold of which remains. There for a good hour did I see her dig, sweep the surface, send the sand flying, and persist, not in making a new gallery, but in seeking the loose sand barrier which should yield to the mere pressure of her head and let her pass easily. Instead of loose materials she finds firm soil not yet disturbed. Warned by this resistance she limits her efforts to exploring the surface, always close to where the door should be, only allowing herself to deviate a few inches. She returns to sound and sweep places already sounded and swept some twenty times, unable to leave her narrow circle, so obstinately convinced is she that the door must be there and nowhere else. With a straw I pushed her gently and repeatedly to another point. She would have none of it, and came back at once to where the door ought to have been. Now and then the gallery, turned into a semi-canal, appeared to attract [[267]]her attention, but very faintly. She would go a few steps along it, still raking, and then return to the entrance. Two or three times I saw her go the whole length of the gallery and reach the cul-de-sac where the larva should be, do a little careless raking, and hurry back where the entrance used to be, and continue searching with a patience which exhausted mine. More than an hour had passed, and still she sought on the site whence the door had disappeared.
What would happen in the presence of the larva? That was the second part of the question. To continue the experiment with the same Bembex would not have offered sufficient guarantee, as the creature, rendered more obstinate by her vain search, seemed possessed by a fixed idea, and this would have interfered with the facts which I wanted to prove. I required a new subject, concerned solely with the impulses of the actual moment. An opportunity soon came. The burrow was uncovered, as I have just said; but I did not touch the contents; larva and food were left in their places,—all was in order inside, the roof only was wanting. Well, with this open dwelling, whose every detail the eye could embrace,—vestibule, gallery, cell at the far end, with the grub and its heap of provender,—this dwelling turned into a roofless gallery at the end of which the larva was moving restlessly, under the hot sun, its mother continued the manœuvres already described. She alighted just where the entrance had been, and there it was that she hunted about and swept the sand—there that she always returned after some hasty attempt elsewhere in a circuit of a few [[268]]inches. No exploration of the gallery—no anxiety for the distressed larva; though the grub, whose delicate skin has just exchanged the gentle moisture of a cave for burning sunshine, is writhing on its heap of chewed Diptera, the mother takes no notice of it. For her it is no more than any one of the objects strewn on the sand,—a little pebble, a clod, a scrap of dried mud,—nothing more. It is undeserving of attention. This tender, faithful mother, who wears herself out in efforts to reach her nursling’s cradle, cares nothing just now but for her entrance door—the door she is used to. That which goes to her maternal heart is the longing to find the well-known passage. Yet the way is open; nothing holds her back, and under her eyes wriggles the grub, the final object of her anxiety. With one spring she would be at the side of the unhappy larva who so needs help. Why does she not rush to her beloved nursling? She could dig a new habitation and get it swiftly underground. But no—she persists in seeking a way which no longer exists, while her son is grilled under her eyes. I was boundlessly surprised by this obtuse maternity, since maternity is the most powerful and most fertile in resource of all feelings which move the animal. Hardly could I have believed my eyes but for endless experiments on the Cerceris and Philanthidæ, as well as on Bembecidæ of different species. Stranger still, the mother, after long hesitation, at length entered the unroofed passage—all that was left of the corridor. She advanced, drew back, and gave a few careless sweeps without stopping. Guided by vague recollections, and perhaps by the smell of [[269]]venison exhaled from the heap of Diptera, she came occasionally as far as the end of the gallery, the very spot where lay the larva. Mother and son had met. At this moment of reunion after long anxiety, were there earnest solicitude, sign of tenderness, or of maternal joy? Whoever thinks so has only to repeat my experiment to convince himself of the contrary. The Bembex did not recognise her larva at all; it was a worthless thing, in her way,—nothing but an embarrassment. She walked over it and trampled it unheeding, as she hurried backwards and forwards. If she wanted to dig at the bottom of the cell, she rudely kicked it behind her,—pushed, upset, expelled it, as she might have treated a large bit of gravel which got in her way while at work. Thus maltreated, the larva bethought itself of defence. I have seen it seize her by one tarsus with no more ceremony than she would have shown in biting the foot of a Dipteron caught by her. The struggle was sharp, but at last the fierce mandibles let go, and the mother flew wildly away with her sharpest hum. This unnatural scene of the son biting the mother, and perhaps even trying to eat her, is unusual, and brought about by circumstances which the observer is not always able to conjure up. What one can always witness is the profound indifference of the Hymenopteron for its offspring, and the brutal disdain with which that inconvenient heap, the grub, is treated. Once she has raked out the far end of the passage, which is done in a moment, the Bembex returns to her favourite point, the threshold, to resume her useless researches. As for the grub, it continues to struggle [[270]]and wriggle wherever the maternal kicks may have landed it. It will perish unaided by its mother, who could not recognise it because she was unable to find the passage she was used to. If we return to-morrow, we shall find it in the gallery, half-broiled by the sun, and already a prey to the flies—once its own prey.
Such is the connection in acts of instinct; one leading to the next in an order that the most serious circumstances have no power to alter. After all, what was the Bembex seeking? Her larva, evidently. But to reach this larva she had to enter the burrow, and to enter the burrow she had to find the door, and the mother persists in seeking this door while the gallery lay open with provender and larva all before her. The ruined abode, the endangered family, were for the moment unimportant; all she could think of was the familiar passage reached through loose sand. Let all go—habitation and inhabitant—if this passage be not found! Her actions are like a series of echoes, awaking one another in a fixed order, the following one only sounding when the preceding has sounded. Not because there was any obstacle; the burrow was all open, but for want of the usual entrance the first action could not take place. That decides everything; the first echo is mute, and so all the rest are silent. What a gulf between intelligence and instinct! Through the ruins of the shattered dwelling a mother guided by intelligence rushes straight to her son; guided by instinct she stops obstinately where once was the door. [[271]]
XX
MASON BEES
Réaumur has dedicated one of his studies to the Chalicodoma of walls, which he calls the Mason Bee. I propose to resume this study, to complete it, and especially to consider it from a point of view entirely neglected by that illustrious observer. And first of all I am tempted to state how I made acquaintance with this Hymenopteron. It was when I first began to teach—towards A.D. 1843. On leaving the Normal School of Vaucluse a few months previously, with my certificate, and the naïve enthusiasm of eighteen, I was sent to Carpentras to manage the primary school belonging to the college. A singular school it was, upon my word, notwithstanding its fine title of “Upper”!—a kind of vast cellar breathing out the damp engendered by a fountain backing on it in the street. Light came in through a door opening outward when the weather allowed of it, and a narrow prison-window, with iron-bars, and little diamond panes set in lead. For seats there was a plank fastened to the walls all round the room; in the middle was a chair guiltless of straw, a blackboard, and a bit of chalk. [[272]]
Morning and evening, at the sound of a bell, there tumbled in some fifty young rascals, who, having failed to master De viris and the Epitome, were devoting themselves, as one said then, to “some good years of French.” The failures at “Rosa, a Rose,” came to me to learn a little spelling. Children were mingled with tall lads at various stages of education, and all distressingly agreed in playing tricks on the master—no older, even younger, than some of themselves.