CHAPTER XIX
THE CLYTHRÆ: THE EGG
Let us leave the long-armed and short-armed to pursue their amorous contests as they please and come to the egg, the main object of my insect-rearing. The Taxicorn Clythra is the first in the field; I see her at working during the last days of May. A most singular and disconcerting batch of eggs is hers! Is it really a group of eggs? I hesitate until I surprise the mother using her hind-legs to finish extracting the strange germ which issues slowly and perhaps laboriously from her oviduct.
It is indeed the Taxicorn Clythra's batch. Assembled in bundles of one to three dozen and each fastened by a slender transparent thread slightly longer than itself, the eggs form a sort of inverted umbel, which dangles sometimes from the trelliswork of the cover, sometimes from the leaves of the twigs that provide the grub with food. The bunch of grains quivers at the least breath.
We know the egg-cluster of the Hemerobius, the object of so many mistakes to the untrained observer. The little Lace-winged Fly with the gold eggs sets up on a leaf a group of long, tiny columns as fine as a spider's thread, each bearing an egg as a capital. The whole resembles pretty closely a tuft of some long-stemmed mildew. Remember also the Eumenes' hanging egg,1 which swings at the end of a thread, thus protecting the grub when it takes its first mouthfuls of the heap of dangerous game. The Taxicorn Clythra provides us with a third example of eggs fitted with suspension-threads, but so far nothing has given me an inkling of the function or the use of this string. Though the mother's intentions escape me, I can at least describe her work in some detail.
1 Cf. The Mason-wasps: chap. i.—Translator's Note.
The eggs are smooth, coffee-coloured and shaped like a thimble. If you hold them to the light, you see in the thickness of their skin five circular zones, darker than the rest and producing almost the same effect as the hoops of a barrel. The end attached to the suspension-thread is slightly conical; the other is lopped off abruptly and the section is hollowed into a circular mouth. A good lens shows us inside this, a little below the rim, a fine white membrane, as smooth as the skin of a drum.
In addition, from the edge of the orifice there rises a wide membranous tab, whitish and delicate, which might be taken for a raised lid. Nevertheless there is no raising of a lid after the eggs are laid. I have seen the egg leave the oviduct; it is then what it will be later, but lighter in colour. No matter: I cannot believe that so complicated a machine can make its way, with all sail set, through the maternal straits. I imagine that the lid-like appendage remains lowered, closing the mouth, until the moment when the egg sees the light. Then and not till then does it rise.
Guided by the rather less complex structure of the eggs of the other Clythræ and of the Cryptocephali, I think of trying to take the strange germ to pieces; and I succeed after a fashion. Under the coffee-coloured sheath, which forms a little five-hooped barrel, is a white membrane. This is what we see through the mouth and what I compared with the skin of a drum. I recognize it as the regulation tunic, the usual envelope of any insect's egg. The rest, the little brown barrel, broached at one end and bearing a raised lid, must therefore be an accessory integument, a sort of exceptional shell, of which I do not as yet know any other example.
The Long-legged Clythra and the Four-spotted Clythra know nothing of packing their eggs in long-stemmed bundles. In June, from the height of the branches in which they are grazing, both of them carelessly allow their eggs to drop to the ground, one by one, here and there, at random and at long intervals, without giving the least thought to their installation. They might be little grains of excrement, unworthy of interest and ejected at hazard. The egg-factory and the dung-factory scatter their products with the same indifference.