They have in exceptional perfection the power of discovering the tubers on which their larvae are nourished.
From truffles dug up in a spoiled condition, peopled with vermin, and placed in that condition, with a bed of fresh sand, in a glass jar, I have in the past obtained a small red beetle, known as the truffle-beetle (_Anisotoma cinnamomea_, Panz.), and various Diptera, among which is a Sapromyzon which, by its sluggish flight and its fragile form, recalls the _Scatophaga scybalaria_, the yellow velvety fly which is found in human excrement in the autumn.

The latter finds its refuge on the surface of the soil, at the foot of a wall or hedge or under a bush; but how does the former know just where the truffle lies under the soil, or at what depth?
To penetrate to that depth, or to seek in the subsoil, is impossible.

Its fragile limbs, barely able to move a grain of sand, its extended wings, which would bar all progress in a narrow passage, and its costume of bristling silken pile, which would prevent it from slipping through crevices, all make such a task impossible.

The Sapromyzon is forced to lay its eggs on the surface of the soil, but it does so on the precise spot which overlies the truffle, for the grubs would perish if they had to wander at random in search of their provender, the truffle being always thinly sown.
The truffle fly is informed by the sense of smell of the points favourable to its maternal plans; it has the talents of the truffle-dog, and doubtless in a higher degree, for it knows naturally, without having been taught, what its rival only acquires through an artificial education.
It would be not uninteresting to follow the Sapromyzon in its search in the open woods.

Such a feat did not strike me as particularly possible; the insect is rare, flies off quickly when alarmed, and is lost to view.