Close to the line of perpetual snow a black variety of vipers has been met with; but none of the serpent race ever cross that line.
The only reptile found within the boundaries of the snowy region is a kind of lizard (Zootoca pyrrhogastra), the only one, perhaps, of all the vertebrata which could live at an elevation above the sea-level of more than 9500 feet, buried in the snow for upwards of ten months.
During the few bright summer weeks, he feeds upon some rare insects and spiders.
The frigid zone is so far the natural habitat of these lizards, that they would rather die of hunger than live in the more genial regions to which men have wished to transplant them. In length they nearly equal our common lizards, but they are not quite so big; their back is of a chesnut brown, marked with black streaks and dots; the throat is bluish; the belly of the male is of a greenish blue, spotted with black, while that of the female is of so lively a red as to have suggested the name of the species, Pyrrhogastra; just as the name of the genus is derived from the circumstance that the young are hatched in the mother's belly, and are born alive like the young of a mammal. This statement, too, holds good with respect to the viper, which also endures the cold of elevated regions.
Inferior Animals.
Our information is still very incomplete so far as relates to the molluscs, the arachnida, and the insects which inhabit the frigid zone. The Alpine snail (Helix Alpicola), so remarkable for its transparency, appears to be the sole mollusc which, in certain localities, attains to an elevation of 7000 feet. It is, however, surpassed by the earthworm, which is not only distributed over the surface of every country, but ascends to the snowy summits of the loftiest mountains. Few animals have their geographical distribution so extended both horizontally and vertically; and only some species of spiders and millepeds keep company with the earthworm.
Among the other inhabitants of the snows have also been observed a dozen species of butterflies,—nearly all diurnal,—for the phalænæ (?), or nocturnal Lepidoptera, appear to be much more sensible to the cold. M. Agassiz saw the "Little Vulcan" (Vanessa urticæ) fluttering in the snowy desert which borders on the glacier of Aar, as if it were completely in its element. The wings of the majority of these butterflies are sombre-coloured; their caterpillars live upon the auriculas, and seem to accomplish their metamorphoses in regions uninhabitable to us. The leaf-wasp (Tenthredo spinacula) appears to deposit its larvæ, at a height of nearly 10,000 feet, in the galls of the Alpine rose (rhododendron ferrugineum and rhododendron hirsutum.)
The coleoptera have also numerous representatives in the region of perpetual snows, with this difference—equally characteristic of other animals—that, upon the southern declivity, they ascend 1000 to 1500 feet higher than on the northern. We may mention, as specially distributed in the topmost zone of the Alpine world:—
The Chrysomela salicina, a pretty little beetle, sometimes blue, sometimes deep green, and finely punctuated, which lives almost exclusively upon a species of dwarf willow (Salix retusa).
The Nebria Escheri, a black beetle, about two thirds of an inch long, with feet and antennæ of a brownish red; and
The Nebria Chevrierii, with rust-coloured feet and antennæ, common in the sources of the Rhine.
Special mention must be made of the Snow-Flea. Do not think we are referring to an insect of the same species as our common fleas: the snow-flea approximates much more closely to the lice family than to the fleas, though it hops like the latter. The history of its discovery dates back as far as 1839. At this epoch, M. Desor, a learned Swiss naturalist, had undertaken some researches upon the glaciers. Accompanied by some friends, he set out from the hospice of the Grimsel, and arrived in the vicinity of the glacier of the Lower Aar. He had commenced his observations, when suddenly he heard Agassiz calling him, and shouting, "Come, come, make haste; here are your Mont Rosa fleas." Desor ran to the spot, and saw under a stone the little creatures whom Agassiz persisted in taking to be veritable lice, pretending they had been accidentally brought to these heights.