"I recognised with extreme joy," says M. Desor, "the little creatures whose loss I had regretted a year before. They are not pretty, but, on the contrary, very ugly. However, they showed, in opposition to the opinion of Agassiz, that they really inhabited the glacier, and were not merely chance visitors. We found them by thousands under other stones. ... Our guide, with whom the glaciers were old acquaintances, had never seen them before, and the tiny creatures excited his astonishment. What surprised us most was the rapidity with which they penetrated into even the most compact ice, till they resembled blood-corpuscles circulating in their vessels. This fact shows that there exist, in the hardest and most transparent ice, certain capillary fissures which escape an unskilled eye: it also proves that the glaciers, on their surface, and down to a certain depth, are by no means incompatible with the development of organised beings."[23]
The tiny insect in question was at first baptized by the name of Desoria saltans (order of the Thysanouræ of Latreille), but has since received definitively the name of Desoria glacialis. It belongs to the family of the Poduræ, singular creatures which, by virtue of their form, are a link between the earwigs and the spiders.
These are its generic characters:—
Fig. 15.—Desoria glacialis; a, natural size; b, enlarged.
The body elongated, cylindrical, garnished with long setiform hairs, and composed of eight segments, six of which are perfectly distinct, and two (the two latter) very short, and scarcely perceptible; four-jointed antennæ, longer than the head; long, slender, cylindrical feet; forked tail, silky, and transversely wrinkled; seven eyes, laterally grouped at the base of each antenna; body without scales.
Fig. 16.—Podura plumbea; a, natural size; b, enlarged.
The Desoria glacialis, a species at present unique, is of a velvety black, and about one-sixth of an inch in length.
The Podura plumbea (or "Spring Tail"), common enough in England, and found under all kinds of stones, will give the reader an idea of the flea of the glaciers.