Fabre's Book of Insects

by Jean-Henri Fabre

The ease with which this larva grips, leaves, and regrips its victim, now here, now there, and always without a wound, shows that the mouth of the Anthrax is not armed with fangs that can dig into the skin and tear it. If the flesh were gashed by pincers of any kind, one or two attempts would be necessary before they could leave go or take hold again; and besides, the skin would be broken. There is nothing of the kind: the grub simply glues its mouth to its prey, and withdraws it. It does not chew its food like the other flesh-eating grub: it does not eat, it inhales.

This remarkable fact led me to examine the mouth [[253]]under the microscope. It is a small conical crater, with yellowish-red sides and very faint lines running round it. At the bottom of this funnel is the opening of the throat. There is not the slightest trace of mandibles or jaws, or any object capable of seizing and grinding food. There is nothing at all but the bowl-shaped opening. I know of no other example of a mouth like this, which I can only compare to a cupping-glass. Its attack is a mere kiss, but what a cruel kiss!

To observe the working of this curious machine I placed a new-born Anthrax-grub, together with its prey, in a glass tube. Here I was able to watch the strange repast from beginning to end.

The Anthrax-grub—the Bee’s uninvited guest—is fixed by its mouth or sucker to any convenient part of the plump Bee-grub. It is ready to break off its kiss suddenly, should anything disturb it, and to resume it as easily when it wishes. After three or four days of this curious contact the Bee-grub, formerly so fat, glossy, and healthy, begins to look withered. Her sides fall in, her fresh colour fades, her skin becomes covered with little folds, and she is evidently shrinking. A week is hardly passed when these signs of exhaustion increase to a startling degree. The victim is flabby and wrinkled, as though borne down by her own weight. If I move her from her place she flops and sprawls like a half-filled indiarubber bottle. But the kiss of the Anthrax goes on [[254]]emptying her: soon she is but a sort of shrivelled bladder, growing smaller and smaller from hour to hour. At length, between the twelfth and fifteenth day, all that remains of the Mason-bee’s larva is a little white grain, hardly as large as a pin’s head.

If I soften this small remnant in water, and then blow into it through a very fine glass tube, the skin fills out and resumes the shape of the larva. There is no outlet anywhere for the compressed air. It is intact: it is nowhere broken. This proves that, under the cupping-glass of the Anthrax, the skin has been drained through its pores.

The devouring grub, in making its attack, chooses its moment very cunningly. It is but an atom. Its mother, a feeble Fly, has done nothing to help it. She has no weapons; and she is quite incapable of penetrating the Mason-bee’s fortress. The future meal of the Anthrax has not been paralysed, nor injured in any way. The parasite arrives—we shall presently see how; it arrives, scarcely visible, and having made its preparations it installs itself upon its monstrous victim, whom it is going to drain to the very husk. And the victim, though not paralysed nor in any way lacking in vitality, lets it have its way, and is sucked dry without a tremor or a quiver of resistance. No corpse could show greater indifference to a bite.

Had the Anthrax-grub appeared upon the scene [[255]]earlier, when the Bee-grub was eating her store of honey, things would surely have gone badly with it. The victim, feeling herself bled to death by that ravenous kiss, would have protested with much wriggling of body and grinding of mandibles. The intruder would have perished. But at the hour chosen so wisely by it all danger is over. Enclosed in her silken sheath, the larva is in the torpid state that precedes her transformation into a Bee. Her condition is not death, but neither is it life. So there is no sign of irritation when I stir her with a needle, nor when the Anthrax-grub attacks her.

There is another marvellous point about the meal of the Anthrax-grub. The Bee-grub remains alive until the very end. Were she really dead it would, in less than twenty-four hours, turn a dirty-brown colour and decompose. But during the whole fortnight that the meal lasts, the butter-colour of the victim continues unaltered, and there is no sign of putrefaction. Life persists until the body is reduced to nothing. And yet, if I myself give her a wound, the whole body turns brown and soon begins to rot. The prick of a needle makes her decompose. A mere nothing kills it; the atrocious draining of its strength does not.

The only explanation I can suggest is this, and it is no more than a suggestion. Nothing but fluids can be drawn by the sucker of the Anthrax through the unpierced skin of the Bee-grub: no part of the breathing-apparatus [[256]]or the nervous system can pass. As these two essentials remain uninjured, life goes on until the fluid contents of the skin are entirely exhausted. On the other hand, if I myself injure the larva of the Bee, I disturb the nervous or the air-conducting system, and the bruised part spreads a taint all over the body.

Liberty is a noble possession, even in an insignificant grub; but it has its dangers everywhere. The Anthrax escapes these dangers only on the condition of being, so to speak, muzzled. It finds its own way into the Bee’s dwelling, quite independently of its mother. Unlike most of the other flesh-eating larvæ it is not fixed by its mother’s care at the most suitable spot for its meal. It is perfectly free to attack its prey where it chooses. If it had a set of carving-tools, of jaws and mandibles, it would meet with a speedy death. It would split open its victim and bite it at random, and its food would rot. Its freedom of action would kill it.