Insect life: Souvenirs of a naturalist

by Jean-Henri Fabre

There is a reason for this surprising choice. What is it? What motives fix a diet which in the strict limits of one and the same entomological order is now composed of ill-smelling kakerlacs, now [[120]]of dry, but well-flavoured crickets, and in yet another of plump grasshoppers, or corpulent ephippigers? I confess that to me it is incomprehensible, and I leave the problem to others. Observe, however, that the Orthoptera rank among insects as the ruminants do among mammalia. Endowed with a mighty paunch and a placid character, they feed on herbage, and easily get corpulent. They are numerous and met with everywhere, slow of gait, and thus easy to catch, and, moreover, of a size just right for prey. Who can say if the Sphegidæ—vigorous hunters which require a large prey—do not find in these ruminants among insects what we find in our domestic ruminants—the sheep and ox, peaceful victims rich in flesh? This is, however, a mere supposition.

[To face p. 120.

SPHEX FLAVIPENNIS ABOUT TO SEIZE GRASSHOPPER

I have more than a supposition in another case, equally important. Do the consumers of Orthoptera ever vary their diet? Should their favourite game fail, can they do with another? Does S. occitanica think that except a fat ephippiger, there is nothing in the wide world worth eating. Does S. albisecta admit nothing but crickets to her table, and S. flavipennis only grasshoppers? Or according to time, place, and circumstance, does each replace the favourite food by some equivalent? It would be of the highest importance to bring forward such facts if they exist, as they would tell us whether the suggestions of instinct are absolute and immutable, or if they vary, and within what limits. It is true that in the cell of a Cerceris are buried most varied species of Buprestids or of the Weevil group, which shows that she has a great latitude of choice; [[121]]but such an extension of hunting ground cannot be supposed for the Sphex, which I have found so faithful to one exclusive prey, invariable for each species, and which, moreover, finds among the Orthoptera kinds of very different shapes. I have, however, had the good fortune to meet with one case—only one—of complete change in the larva’s food, and I mention it the more willingly in the archives of the Sphegidæ because such facts, scrupulously observed, will one day be corner-stones for him who may desire to build the psychology of instinct on solid foundations.

This is my fact. The scene is on a jetty by the Rhône. On one side is the great river, with its thunder of waters, on the other, a dense thicket of osiers, willows, and reeds, and between the two a narrow path with a bed of fine sand. A yellow-winged Sphex appears, hopping and dragging its prey along. What do I see! It is no grasshopper, but a common Acridian! And yet the Hymenopteron really is the Sphex so well known to me (S. flavipennis), the energetic huntress of grasshoppers! I can hardly believe my eyes. The burrow is not far off; she enters and stores her booty. I seat myself, determined to await a new expedition—wait hours if need be to see if so extraordinary a capture is repeated. Seated there I occupy the whole width of the path. Two simple conscripts come up, new-clipped, with that incomparable, automaton-look conferred by the first days of barrack life. They are chattering together—no doubt talking of their homes and the girls they left behind them; each is peeling a willow switch with a [[122]]knife. A fear seizes me; ah! it is not easy to try an experiment on the public way, where, when some fact watched for during long years does present itself, a passer-by may disturb or annihilate chances which may never occur again! I rise anxiously to make way for the conscripts; I withdraw into the osier bed, and leave the narrow way free. To do more was not prudent; to say, “My good fellows, do not go that way,” would have made bad worse. They would have supposed some snare hidden in the sand, and questions would have arisen to which no reply that would satisfy them could have been given. My request, moreover, would have turned these idlers into lookers-on, very embarrassing company in such studies, so I resolved to say nothing, and trust to my luck. Alas! alas! my star betrayed me. The heavy regulation boot was planted exactly on the Sphex’s roof. A shudder ran through me as though I had myself received the impress of the iron heel.

The conscripts gone I proceeded to the salvage of the contents of the ruined burrow. There was the Sphex mutilated by the pressure, and there were not only the cricket which I saw carried down, but two others—three crickets in all instead of the usual grasshoppers. What was the reason of this strange variation? Were there no grasshoppers near the burrow, and did the distressed Hymenopteron do the best she could with Acridians—contenting herself as it were with blackbirds for want of thrushes, as the proverb says? I hesitate to believe it, for there was nothing in the neighbourhood to denote absence of her favourite game. Some happier means may [[123]]unriddle this new problem. In any case S. flavipennis, either from imperious necessity, or from motives unknown to me, sometimes replaces her favourite prey, the grasshopper, by another, the Acridian, altogether unlike outwardly to the former, but still an Orthopteron.

The observer on whose authority Lepeletier de St. Fargeau speaks of this Sphex’s habits witnessed in Africa, near Oran, a similar storing of Acridians. S. flavipennis was surprised by him dragging along an Acridian. Was it an accidental case, like the one seen by me on the banks of the Rhône? Was it the exception, or was it the rule? Were grasshoppers wanting around Oran, and did the Hymenopteron replace them by Acridians? Circumstances compel me to ask the question without finding a reply.

Here should be interpolated a certain passage from Lacordaire’s Introduction to Entomology,[1] against which I long to raise my voice in protest. Here it is: “Darwin, who has written a book on purpose to prove the identity of the intellectual principle which produces action in man and animals, walking one day in his garden noticed on the ground in a shady walk a Sphex which had just caught a fly nearly as big as itself. He saw it cut off with its mandibles the victim’s head and abdomen, keeping only the thorax, to which the wings remained attached. It then flew away, but a breath of wind striking the fly’s wings twirled the Sphex round, [[124]]and hindered its progress. Thereupon it lit again on the walk, cut off first one wing and then the other from the fly, and having thus removed the cause of its difficulties, flew off with the remainder of its prey. This fact indicates manifest signs of reasoning. Instinct might have induced the Sphex to cut off the wings of its victim before transporting it to the nest, as do some species of the same genus, but here were consecutive ideas and results of those ideas quite inexplicable, unless one admits the intervention of reason.”

This little story, which so lightly bestows reason on an insect, is wanting not only in truth but in mere probability—not in the act itself, which I do not question at all, but in its motives. Darwin saw what he relates, but he was mistaken as to the hero of the drama; as to the drama itself, and as to its meaning—profoundly mistaken, and I can prove it.