Fabre's Book of Insects

by Jean-Henri Fabre

The other Bee, who is very much more frequently seen and is called Anthophora pilipes, leaves the opening of her corridor bare. The chinks between the stones in old walls and abandoned hovels, or exposed surfaces of sand stone or marl, are found suitable for her labours; [[158]]but the favourite spots, those to which the greatest number of swarms resort, are straight stretches of ground exposed to the south, such as occur in the cuttings of deeply-sunken roads. Here, over areas many yards in width, the wall is drilled with a multitude of holes, which give to the earthy mass the look of some enormous sponge. These round holes might have been made with a gimlet, so regular are they. Each is the entrance to a winding corridor, which runs to the depth of four or five inches. The cells are at the far end. If we wish to watch the labours of the industrious Bee we must visit her workshop during the latter half of May. Then—but at a respectful distance—we may see, in all its bewildering activity, the tumultuous, buzzing swarm, busied with the building and provisioning of the cells.

But it has been most often during the months of August and September, the happy months of the summer holidays, that I have visited the banks inhabited by the Anthophora. At this season all is silent near the nests: the work has long been completed: and numbers of Spiders’ webs line the crevices or plunge their silken tubes into the Bees’ corridors. That is no reason, however, for hastily abandoning the city that was once so full of life and bustle, and now appears deserted. A few inches below the surface, thousands of grubs are imprisoned in their cells of clay, resting until the coming [[159]]spring. Surely these grubs, which are paralysed and incapable of self-defence, must be a temptation—fat little morsels as they are—to some kind of parasite, some kind of insect stranger in search of prey. The matter is worth inquiring into.

Two facts are at once noticeable. Some dismal-looking Flies, half black and half white, are flying indolently from gallery to gallery, evidently with the object of laying their eggs there. Many of them are hanging dry and lifeless in the Spiders’ webs. At other places the entire surface of a bank is hung with the dried corpses of a certain Beetle, called the Sitaris. Among the corpses, however, are a few live Beetles, both male and female. The female Beetle invariably disappears into the Bees’ dwelling. Without a doubt she, too, lays her eggs there.

If we give a few blows of the pick to the surface of the bank we shall find out something more about these things. During the early days of August this is what we shall see: the cells forming the top layer are unlike those at a greater depth. The difference is owing to the fact that the same establishment is used by two kinds of Bee, the Anthophora and the Osmia.

The Anthophoræ are the actual pioneers. The work of boring the galleries is wholly theirs, and their cells are right at the end. If they, for any reason, leave the [[160]]outer cells, the Osmia comes in and takes possession of them. She divides the corridors into unequal and inartistic cells by means of rough earthen partitions, her only idea of masonry.

The cells of the Anthophora are faultlessly regular and perfectly finished. They are works of art, cut out of the very substance of the earth, well out of reach of all ordinary enemies; and for this reason the larva of this Bee has no means of spinning a cocoon. It lies naked in the cell, whose inner surface is polished like stucco.

In the Osmia’s cells, however, means of defence are required, because they are at the surface of the soil, are roughly made, and are badly protected by their thin partitions. So the Osmia’s grubs enclose themselves in a very strong cocoon, which preserves them both from the rough sides of their shapeless cells and from the jaws of various enemies who prowl about the galleries. It is easy, then, in a bank inhabited by these two Bees, to recognise the cells belonging to each. The Anthophora’s cells contain a naked grub: those of the Osmia contain a grub enclosed in a cocoon.

Now each of these two Bees has its own especial parasite, or uninvited guest. The parasite of the Osmia is the black-and-white Fly who is to be seen so often at the entrance to the galleries, intent on laying her eggs within them. The parasite of the Anthophora is the [[161]]Sitaris, the Beetle whose corpses appear in such quantities on the surface of the bank.

If the layer of Osmia-cells be removed from the nest we can observe the cells of the Anthophora. Some will be occupied by larvæ, some by the perfect insect, and some—indeed many—will contain a singular egg-shaped shell, divided into segments with projecting breathing-pores. This shell is extremely thin and fragile; it is amber-coloured, and so transparent that one can distinguish quite plainly through its sides a full-grown Sitaris, struggling as though to set herself at liberty.

What is this curious shell, which does not appear to be a Beetle’s shell at all? And how can this parasite reach a cell which seems to be inaccessible because of its position, and in which the most careful examination under the magnifying-glass reveals no sign of violence? Three years of close observation enabled me to answer these questions, and to add one of its most astonishing chapters to the story of insect life. Here is the result of my inquiries.