Fabre's Book of Insects

by Jean-Henri Fabre

The road shimmers like a sheet of molten steel. From the dusty, melancholy olive-trees rises a mighty, throbbing hum, the concert of the Cicadæ, who sway and rustle with increasing frenzy as the temperature increases. The Cicada of the Ash adds its strident scrapings to the single note of the Common Cicada. This is the moment! For five or six weeks, oftenest in the morning, sometimes in the afternoon, I set myself to explore the rocky waste.

There were plenty of the nests I wanted, but I could not see a single Anthrax on their surface. Not one settled in front of me to lay her egg. At most, from time [[267]]to time, I could see one passing far away, with an impetuous rush. I would lose her in the distance; and that was all. It was impossible to be present at the laying of the egg. In vain I enlisted the services of the small boys who keep the sheep in our meadows, and talked to them of a big black Fly and the nests on which she ought to settle. By the end of August my last illusions were dispelled. Not one of us had succeeded in seeing the big black Fly perching on the dome of the Mason-bee.

The reason is, I believe, that she never perches there. She comes and goes in every direction across the stony plain. Her practised eye can detect, as she flies, the earthen dome which she is seeking, and having found it she swoops down, leaves her egg on it, and makes off without setting foot on the ground. Should she take a rest it will be elsewhere, on the soil, on a stone, on a tuft of lavender or thyme. It is no wonder that neither I nor my young shepherds could find her egg.

Meanwhile I searched the Mason-bees’ nests for grubs just out of the egg. My shepherds procured me heaps of the nests, enough to fill baskets and baskets; and these I inspected at leisure on my work-table. I took the cocoons from the cells, and examined them within and without: my lens explored their innermost recesses, the sleeping larva, and the walls. Nothing, nothing, nothing! For a fortnight and more nests were searched [[268]]and rejected, and heaped up in a corner. My study was crammed with them. In vain I ripped up the cocoons; I found nothing. It needed the sturdiest faith to make me persevere.

At last I saw, or seemed to see, something move on the Bee’s larva. Was it an illusion? Was it a bit of down stirred by my breath? It was not an illusion; it was not a bit of down; it was really and truly a grub! But at first I thought the discovery unimportant, because I was so greatly puzzled by the little creature’s appearance.

In a couple of days I was the owner of ten such worms and had placed each of them in a glass tube, together with the Bee-grub on which it wriggled. It was so tiny that the least fold of skin concealed it from my sight. After watching it one day through the lens I sometimes failed to find it again on the morrow. I would think it was lost: then it would move, and become visible once more.

For some time the belief had been growing in me that the Anthrax had two larval forms, a first and a second, the second being the form I knew, the grub we have already seen at its meals. Was this new discovery, I asked myself, the first form? Time showed me that it was. For at last I saw my little worms transform themselves into the grub I have already described, and make their first start at draining their victims with kisses. [[269]]A few moments of satisfaction like those I then enjoyed make up for many a weary hour.

This tiny worm, the first form or “primary larva” of the Anthrax, is very active. It tramps over the fat sides of its victim, walking all round it. It covers the ground pretty quickly, buckling and unbuckling by turns, very much after the manner of the Looper-caterpillar. Its two ends are its chief points of support. When walking it swells out, and then looks like a bit of knotted string. It has thirteen rings or segments, including its tiny head, which bristles in front with short, stiff hairs. There are four other pairs of bristles on the lower surface, and with the help of these it walks.

For a fortnight the feeble grub remains in this condition, without growing, and apparently without eating. Indeed, what could it eat? In the cocoon there is nothing but the larva of the Mason-bee, and the worm cannot eat this before it has the sucker or mouth that comes with the second form. Nevertheless, as I said before, though it does not eat it is far from idle. It explores its future dish, and runs all over the neighborhood.

Now, there is a very good reason for this long fast. In the natural state of the Anthrax-grub it is necessary. The egg is laid by the mother on the surface of the nest, at a distance from the Bee’s larva, which is protected by a thick rampart. It is the business of the new-born [[270]]grub to make its way to its provisions, not by violence, of which it is incapable, but by patiently slipping through a maze of cracks. It is a very difficult task, even for this slender worm, for the Bee’s masonry is exceedingly compact. There are no chinks due to bad building, no cracks due to the weather. I see but one weak point, and that only in a few nests: it is the line where the dome joins the surface of the stone. This weakness so seldom occurs that I believe the Anthrax-grub is able to find an entrance at any spot on the dome of the Bee’s nest.