Under natural conditions, a preliminary run round may well be indispensable. There, sites as soft as my bed of heath-mould, purged of all hard bodies and finely sifted, are rare. There, on the other hand, coarse soils, on which the microscopic mattock can make no impression, are frequent. The grub has to roam at random, to walk about for some time before finding a suitable place. No doubt many even die, exhausted by their fruitless search. A journey of exploration, in a country a few inches across, forms part, therefore, of the young Cicada’s curriculum. In my glass jar, so sumptuously furnished, the pilgrimage is uncalled for. No matter: [[107]]it has to be performed according to the time-honoured rites.
My gadabouts at last grow calm. I see them attack the earth with the hooked mattocks of their fore-feet, digging into it and making the sort of excavation which the point of a thick needle would produce. Armed with a magnifying-glass, I watch them wielding their pick-axes, watch them raking an atom of earth to the surface. In a few minutes a well has been scooped out. The little creature goes down it, buries itself and is henceforth invisible.
Next day I turn out the contents of the pot, without breaking the clod held together by the roots of the thyme and the wheat. I find all my larvæ at the bottom, stopped from going farther by the glass. In twenty-four hours they have traversed the entire thickness of the layer of earth, about four inches. They would have gone even lower but for the obstacle at the bottom.
On their way they probably came across my thyme- and wheat-roots. Did they stop to take a little nourishment by driving in their suckers? It is hardly probable. A few of these rootlets are trailing at the bottom of the empty pot. Not one of my [[108]]six prisoners is installed on them. Perhaps in overturning the glass I have shaken them off.
It is clear that underground there can be no other food for them than the juice of the roots. Whether full-grown or in the larval stage, the Cicada lives on vegetables. As an adult, he drinks the sap of the branches; as a larva, he sucks the sap of the roots. But at what moment is the first sip taken? This I do not yet know. What goes before seems to tell us that the newly-hatched grub is in a greater hurry to reach the depths of the soil, sheltered from the coming colds of winter, than to loiter at the drinking-bars encountered on the way.
I put back the clod of heath-mould and for the second time place the six exhumed larvæ on the surface of the soil. Wells are dug without delay. The grubs disappear down them. Finally I put the pot in my study-window, where it will receive all the influences of the outer air, good and bad alike.
A month later, at the end of November, I make a second inspection. The young Cicadæ are crouching, each by itself, at the bottom of the clod of earth. They are not [[109]]clinging to the roots; they have not altered in appearance or in size. I find them now just as I saw them at the beginning of the experiment, only a little less active. Does not this absence of growth during the interval of November, the mildest month of winter, seem to show that no nourishment is taken throughout the cold season?
The young Sitaris-beetles,[11] those other animated atoms, as soon as they issue from the egg at the entrance to the Anthophora’s[12] galleries, remain in motionless heaps and spend the winter in complete abstinence. The little Cicadæ would appear to behave in much the same manner. Once buried in depths where there is no fear of frosts, they sleep, solitary, in their winter-quarters and await the return of spring before broaching some root near by and taking their first refreshment.
I have tried, but without success, to confirm by actual observation the inferences to be drawn from the above results. In the spring, in April, for the third time I unpot my plantation. I break up the clod and [[110]]scrutinize it under the magnifying-glass. I feel as if I were looking for a needle in a haystack. At last I find my little Cicadæ. They are dead, perhaps of cold, notwithstanding the bell-glass with which I had covered the pot; perhaps of starvation, if the thyme did not suit them. The problem is too difficult to solve; I give it up.
To succeed in this attempt at rearing one would need a very wide and deep bed of earth, providing a shelter from the rigours of winter, and, because I do not know which are the insect’s favourite roots, there would also have to be a varied vegetation, in which the little larvæ could choose according to their tastes. These conditions are quite practicable; but how is one afterwards to find in that huge mass of earth, measuring a cubic yard at least, the atom which I have so much trouble in distinguishing in a handful of black mould? And, besides, such conscientious digging would certainly detach the tiny creature from the root that nourishes it.