Ammophila

“ The solitary habits of the Ammophila,—their being scattered singly over wide spaces, and their being almost always met with by mere chance,—almost forbid, as in the case of Sphex occitanica, any experiment being prepared beforehand. Long must a chance be watched for and awaited with unalterable patience, and one must know how instantly to profit by it when at last it comes just when least expected. ”

“ But the Sandy Ammophila and especially the Hairy Ammophila capture enormous victims, whose weight, as I have said, is fifteen times that of the kidnapper. Will this giant prey be treated in the same manner as the frail Measuring-worm? Will one dagger-thrust be sufficient to subdue the monster and render it incapable of doing harm? Will the horrid Grey Worm, lashing the walls of the cell with its powerful tail, not endanger either the egg or the little grub? ”

“ The Ammophila is born a finished desnucador even as we are born feeders at our mother’s breast. The nurseling uses its suction-pump, the Ammophila her dart, without ever being taught; and both are past masters of the difficult art from the first attempt. There we have instinct, the unconscious impulse that forms an essential part of the conditions of life and is handed down by heredity in the same way as the rhythmic action of the heart and lungs. ”

“ I find the Sandy Ammophila mentioned as hatching on the 5th of June and the Silvery Ammophila on the 20th of that month; but my records contain not a word that relates to the hatching of the Hairy Ammophila. It is a detail which, by an oversight, has never been cleared up. The dates given for the other two species come under the general law, which lays down that the perfect insect shall appear during the hot season. I fix the same period, by analogy, as that for the Hairy Ammophila’s emergence from the cocoon. ”

“ As two are required there must be another journey and another stopping up of the burrow, before the final one, which is of a more solid nature, occupying, sometimes, as much as twenty minutes. In thus bringing her labours to a conclusion, Ammophila often shows a wonderful degree of intelligent foresight—foresight we must term it if we admit the intelligence; for sometimes she will drag a leaf over the entrance to the tunnel, though now filled in, or taking a stone as large as her head in her mandibles, will pound down the earth with it to make it firm and compact. ”

“ The Ammophila operates in a similar fashion, with this difference, that her surgery is much more complex, much more difficult, because of the peculiar organization of her victim. The honours are on her side again when we consider the delicacy of the result obtained. Her caterpillar is not a corpse, like the Ox whose spinal cord is cut; it is alive, but incapable of movement. The insect here is man’s superior in all respects. ”

“ The Hairy Ammophila gives her larva a single caterpillar, a large one, paralysed by as many pricks of her sting as it has nervous centres in its thorax and abdomen. Her surgical skill in subduing the monster is instinct, displayed in a form that quashes any inclination to see in it an acquired habit. In an art that can leave no one to practise it in the future unless that one be perfect at the outset, of what avail are lucky chances, atavistic tendencies, or the mellowing hand of time? ”

“ That which governs the whole history of the Ammophila, and more especially attracted my attention, was the way in which the insect masters its prey and plunges it into the harmless state required for the safety of the larva. The prey, a caterpillar, is very differently organised from the victims which we have hitherto seen sacrificed—Buprestids, Weevils, Grasshoppers, and Ephippigers. ”

“ She may either fly or run back, for her legs are as highly developed as her wings—she is in fact a very perfect athlete. The process of excavation is now continued, there is more burrowing, more flying away with the earth dug out, and before long the nursery-vault is completed. The next thing is to find caterpillars for it, but before flying away to look for one, Ammophila carefully conceals the entrance to her tunnel with pellets of earth, which she often brings from a distance, and will not be satisfied with unless they seem well adapted for their purpose. ”

“ We see the same habit in other genera where the [35] mother continually passes in and out, as in Bembex and Oxybelus.
Fabre thinks that hirsuta has the habit, unusual for Ammophila, of catching her prey first and then digging the hole in which she bestows it. As she takes only one large caterpillar she is thus relieved of the necessity of closing the nest more than once. ”

“ The Ammophila excavates alone, deliberately, with no joyous ardour. As usual, the anterior tarsi do duty as rakes and the mandibles as mining tools. If some grain of sand offer too much resistance, you may hear rising from the bottom of the well a kind of shrill grinding sound, produced by the vibration of the wings and entire body as if to express the insect’s struggles. Frequently the Hymenopteron comes up with a load of refuse in its jaws, some bit of gravel which it drops as it flies some little way off, in order not to block up the place. ”

“ If the caterpillar's jaws open and threaten, the Ammophila stills them by biting the neck; if they are already growing quiescent, she refrains. Without being indispensable, this operation is useful at the moment of carting the prey. The caterpillar, too heavy to be carried on the wing, is dragged, head first, between the Ammophila's legs. If the mandibles are working, the least clumsiness may render them dangerous to the carrier, who is exposed to their bite without any means of defence. ”

“ Lastly, the Ammophila, opening the forceps of her mandibles to their full width, seizes the caterpillar’s head and crunches it, squeezes it with a series of leisurely movements, without creating a wound. These squeezings follow upon one another with deliberate slowness: the insect seems to try each time to learn the effect produced; it stops, waits, and then resumes the attack. This manipulation of the brain, to attain the desired end, must have certain limits which, if exceeded, would bring about death and speedy putrefaction. ”

“ Settled on the monster’s back the Ammophila bends her abdomen, and methodically, deliberately—like a surgeon thoroughly familiar with the anatomy of his subject—plunges a lancet into the ventral surface of every segment, from the first to the last. Not one ring is omitted; with or without feet each is stabbed in due order from the front to the back.
This is what I saw with all the leisure and ease [218] required for an irreproachable observation. The Hymenopteron acts with a precision of which science might be jealous; it knows what man but rarely knows ”

“ The Ammophila does not as a rule trouble about her burrow, or at least does not complete it, until she has caught her caterpillar. During the mining-operations, the game is laid somewhere high up, out of reach of the Ants, on some tuft of grass, or the twigs of a shrub, whither the huntress, from time to time, stopping her well-sinking, hastens to see if her quarry is still there. ”

“ We immediately think of the antennae. The antennae are what we always fall back upon when the insect's actions are not quite clear to us; we gladly put down to them whatever is most necessary to our arguments. For that matter, I had plenty of fairly good reasons for suspecting them of containing the sense of direction. When the Hairy Ammophila (A Sand-wasp who hunts the Grey Worm, or Caterpillar of the Turnip-moth, to serve as food for her grubs. For other varieties of the Ammophila, cf. "Insect Life": chapter 15.—Translator's Note.) ”

“ It forms a right angle with the supporting axis, so much so that the whole weight of the insect, which has turned itself into the arm of a lever, rests upon the mandibles.
The Ammophila sleeps extended in space by virtue of its mighty jaws. It takes an animal to think of a thing like that, which upsets all our preconceived ideas of repose. Should the threatening storm burst, should the stalk sway in the wind, the sleeper is not troubled by her swinging hammock; at most, she presses her fore-legs for a moment against the tossed mast. ”

“ We move in a vicious circle: to produce good we must invoke the aid of evil. The hostile band brings the friendly troop to our fields; but the second cannot live without the first; and the two show an even balance in numbers. If the Grey Worm abound, the Ammophila finds copious provender for her grubs and her race prospers; if the Grey Worm be rare, the Ammophila’s offspring decrease and disappear. This balance between prosperity and decadence is the immutable law that governs the proportions between devourers and devoured. [354]
1 Burying-beetles.—Translator’s Note. ”

“ At a later hour in the day, or even merely when the sun has left the place where the burrow has just been bored, the Ammophila invariably visits the little heap of stones placed in reserve during the excavating, with the object of choosing a bit to suit her. If there is nothing that satisfies her needs, she explores the neighbourhood and soon discovers what she wants, a small flat stone slightly larger in diameter than the mouth of her hole. ”

“ WHILE Ammophila provides caterpillars for her larva, and Bembex, after the manner of the social wasps, feeds her young from day to day on dead flies, the Pompilidæ, so far as their habits are known, all prey upon spiders. The family is a large one in the United States, one hundred and twenty-seven species having been described. The members of the group differ in size, color, and habits, and the individuals of the same species show the very considerable amount of variation which seems common to all those groups of animals which have been carefully studied. ”

“ Heredity does not hand down the art of killing by severing the spinal marrow: no man is born a cattle-slayer by the desnucador’s method.
Now here is the Ammophila, a slayer of caterpillars by a far more cunning method. Where are the professors of the art of stinging? There are not any. When the Wasp rends her cocoon and issues from underground, her predecessors have long ceased to live; she herself will perish without seeing her successors. Once the larder is stocked and the egg laid, all connection with the offspring ends ”

“ Yet this exploit of topographical memory is accomplished, and sometimes with a precision which left me amazed. The insect made straight for the burrow as if long used to every path in the neighbourhood; but at other times there would be long visitation and repeated searches.
If the difficulty become serious, the prey, which is an embarrassing load in a hurried exploration, is laid in some obvious place, on a tuft of thyme or grass, where it can be easily seen when wanted. Freed from this burden the Ammophila resumes an active search. ”

“ A like migration to a short distance seems to me to have caused the assemblage of Ammophila on the top of Mont Ventoux. I have proved that this insect spends the winter in the perfect state, sheltering somewhere and awaiting April to build its nest. Like the lark it must take precautions against the cold season; though capable of fasting till flowers return, the chilly thing must find protection against the deadly attacks of the cold. ”

“ When the digger-wasp, Ammophila, stings its caterpillar victim in just the right places to ensure paralysis without death it acts by instinct, it must not be considered to have any knowledge like that of the learned entomologist who would know the vulnerable places from the outside—from detailed observations of all parts of the caterpillar body. ”

“ It is true that many allow themselves a more varied bill of fare, but only within the limits of one entomological group: thus the Weevil and Buprestis hunters prey upon any species proportioned to their strength. Were the Hairy Ammophila to make a change in her diet, that would be her case too. ”

“ If the mandibles try to snap, if the legs give a kick or two, they find nothing in front of them: the Ammophila's egg is at the opposite side. The tiny grub is thus able, as soon as it hatches, to dig into the giant's belly in full security.
How different are the conditions in the Eumenes' cell. The caterpillars are imperfectly paralysed, perhaps because they have received but a single stab; they toss about when touched with a pin; they are bound to wriggle when bitten by the larva. ”

“ In the case of all four the burrow is a vertical shaft, a sort of well, possessing at most the diameter of a thick goose-quill and a depth of about two inches. At the bottom is the cell, which is always solitary and consists of a mere widening of the entrance-shaft. It is, when all is said, a poor lodging, obtained economically, in one day’s work; the larva will find no protection there against the winter except from the four wrappers of its cocoon, copied from that of the Sphex. The Ammophila digs by herself, quietly, without hurrying, without any joyous enthusiasm. ”

“ They are, moreover, the most remarkable of all genera in their stinging habits, and few things have given us deeper pleasure than our success in following the activities and penetrating the secrets of their lives. In our neighborhood we have but two species of Ammophila, urnaria Cresson and gracilis Cresson, both of them being very slender bodied wasps of about an inch in length, gracilis all black, and urnaria with a red band around the front end of the abdomen. ”