When the transformation is accomplished, what perspicacity on the part of the inexperienced insect, when it abandons its cosy home to seek a refuge under the rude shelter of the stones, foreseeing the winter which will ruin the natal villa! We possess the almanac of the past, telling us of the almanac of the future. The insect, with no records of the vicissitudes of the seasons; the insect, born in the dog-days, in the blazing heat of summer: the insect feels instinctively that this [[61]]period of solar intoxication will not last; it knows, though it has never seen it happen, that its house is doomed soon to collapse; and it makes off before the roof falls in.
For a Weevil, this is fine, magnificent. We might well envy the creature’s wisdom in being thus awake to the calamities of the future.
However devoid of industry she may be, the least-gifted mother none the less submits an insoluble problem for our consideration. What is it that leads her to lay her eggs at spots where the larvæ will find food to their liking?
The Pieris[4] goes to the cabbage, in which she has no personal interest. The plant, compressed into a head, has not yet flowered. Besides, its modest yellow blossoms have no greater attraction for the Butterfly than an infinity of other flowers distributed broadcast. The Vanessa[5] goes to the nettle, on which her caterpillars will feast, but on which the adult insect finds nothing to suck.
When, in the summer gloaming, the Pine Cockchafer has long been whirling in the nuptial ballet around her favourite tree, she refreshes herself after her fatigue by nibbling a few pine-needles; then, with impetuous flight, she goes in search of [[62]]some bare, sandy tract where the grass-roots lie decaying. Here, as often as not, there is no resinous aroma, there are no more pine-trees, the delight of the plumed beauty; and it is in this place, where nothing appeals to her own needs, that the mother, half-buried in the ground, will lay her egg.
That ardent lover of roses and hawthorn-blossom, the Golden Cetonia, leaves the luxury of the flowers, to burrow in the shame of putrescence. She repairs to the compost-heap, but is certainly not tempted by any dish to her taste. She cannot sip honey there nor intoxicate herself with perfumed essences. Another reason draws her to this corruption.
At first sight it would seem as if these strange instincts might be explained by the larva’s diet, of which the adult would retain a lively recollection. The caterpillar of the Pieris fed on cabbage-leaves; the caterpillar of the Vanessa fed on nettle-leaves; and each of the two Butterflies, endowed with a faithful memory, exploits the plant which has no attraction for her now, but which was a treat for her in her infancy.
In the same way, the Cetonia dives into the heap of leaf-mould because she remembers the feasts of former days, when she was a grub in the midst of the fermenting vegetable matter; and the Pine Cockchafer seeks the sandy tracts covered with lean tufts of grass, because she remembers [[63]]her youthful revels underground amid the decaying rootlets.
Such a memory would be almost admissible if the adult’s diet were the same as the larva’s. We can more or less understand the Dung-beetle, who, herself feeding upon animal droppings, makes them into canned provisions for her family. The diet of maturity and that of infancy are linked as though each were a reminiscence of the other. Uniformity offers a very simple solution of the food-problem.
But what shall we say of the Cetonia passing from the flowers to the sordid refuse of the decayed leaves? Above all, what shall we say of the Hunting Wasps? These fill their own crops with honey and feed their youngsters on prey!