CHAPTER V
THE CICADA: THE LAYING AND THE HATCHING OF THE EGGS
The Common Cicada entrusts her eggs to small dry branches. All those which Réaumur examined and found to be thus tenanted were derived from the mulberry-tree: a proof that the person commissioned to collect these eggs in the Avignon district was very conservative in his methods of search. In addition to the mulberry-tree, I, on the other hand, find them on the peach, the cherry, the willow, the Japanese privet and other trees. But these are exceptions. The Cicada really favours something different. She wants, as far as possible, tiny stalks, which may be anything from the thickness of a straw to that of a lead-pencil, with a thin ring of wood and plenty of pith. So long as these conditions are fulfilled, the actual plant matters little. I should have to draw up a list of all the semiligneous flora [[83]]of the district were I to try and catalogue the different supports used by the Cicada when laying her eggs. I shall content myself with naming a few of them in a note, to show the variety of sites of which she avails herself.[1]
The sprig occupied is never lying on the ground; it is in a position more or less akin to the perpendicular, most often in its natural place, sometimes detached, but in that case sticking upright by accident. Preference is given to a good long stretch of smooth, even stalk, capable of accommodating the entire laying. My best harvests are made on the sprigs of Spartium junceum, which are like straws crammed with pith, and especially on the tall stalks of Asphodelus cerasiferus, which rise for nearly three feet before spreading into branches.
The rule is for the support, no matter what it is, to be dead and quite dry. Nevertheless my notes record a few instances of [[84]]eggs confided to stalks that are still alive, with green leaves and flowers in bloom. It is true that, in these highly exceptional cases, the stalk itself is of a pretty dry variety.[2]
The work performed by the Cicada consists of a series of pricks such as might be made with a pin if it were driven downwards on a slant and made to tear the ligneous fibres and force them up slightly. Any one seeing these dots without knowing what produced them would think first of some cryptogamous vegetation, some Sphæriacea swelling and bursting its skin under the growth of its half-emerging perithecia.
If the stalk be uneven, or if several Cicadæ have been working one after the other at the same spot, the distribution of the punctures becomes confused and the eye is apt to wander among them, unable to perceive either the order in which they were made or the work of each individual. One characteristic is never missing, that is the slanting direction of the woody strip ploughed up, which shows that the Cicada always works in an upright position and drives her implement [[85]]downwards into the twig, in a longitudinal direction.
If the stalk be smooth and even and also of a suitable length, the punctures are nearly equidistant and are not far from being in a straight line. Their number varies: it is small when the mother is disturbed in her operation and goes off to continue her laying elsewhere; it amounts to thirty or forty when the line of dots represents the total amount of eggs laid. The actual length of the row for the same number of thrusts likewise varies. A few examples will enlighten us in this respect: a row of thirty measures 28 centimetres[3] on the toad-flax, 30[4] on the gum-succory and only 12[5] on the asphodel.
Do not imagine that these variations in length have to do with the nature of the support: there are plenty of instances that prove the contrary; and the asphodel, which in one case shows us the punctures that are closest together, will in other cases show us those which are farthest removed. The distance between the dots depends on circumstances which cannot be explained, but [[86]]especially on the caprice of the mother, who concentrates her laying more at one spot and less at another according to her fancy. I have found the average measurement between one hole and the next to be 8 to 10 millimetres.[6]
Each of these abrasions is the entrance to a slanting cell, usually bored in the pithy portion of the stalk. This entrance is not closed, save by the bunch of ligneous fibres which are parted at the time of the laying but which come together again when the double saw of the ovipositor is withdrawn. At most, in certain cases, but not always, you see gleaming through the threads of this barricade a tiny glistening speck, looking like a glaze of dried albumen. This can be only an insignificant trace of some albuminous secretion which accompanies the eggs or else facilitates the play of the double boring-file.