The geographical distribution of this genus, of which some twenty species are known, is very remarkable. The majority live in Mexico and in the United States, a few are found in Colombia and Northern Peru (S. altamazonicus and Plethodon platense being the only Urodeles hitherto recorded from south of the equator), one in Hayti (S. infuscatus), two (S. subpalmatus and S. uniformis) in Costa Rica, and S. fuscus in Europe.
S. bilineatus is a little newt under 4 inches in length–60-95 mm.–found in the Atlantic States. It is brownish-yellow above, with a black lateral line extending from the eye to nearly the end of the tail. The under parts are bright yellow. It lives on land, in damp places, concealed during the daytime under stones or old trees, whence it emerges after a rain or in the dusk of evening.
According to H. H. Wilder,[[49]] "the eggs are deposited in May and June in a single layer upon the lower side of submerged stones, each batch containing 30 to 50 eggs. The stones which are suitable for this purpose must be in the form of an arch, allowing the water to flow beneath. They are generally in the more rapidly flowing portions of the brook, but the depth of water must be such that the eggs are at all times entirely submerged. They are attached to the stone by gelatinous threads, proceeding from the outer envelope, and although they are generally contiguous, they are each attached separately." The eggs are holoblastic. The larvae hatch early and continue for a long time in the larval state, probably two or three years.
S. porphyriticus s. salmoneus.–Yellowish-brown or purplish-grey above with tiny darker dots and markings. The sides of the body are salmon-coloured, with a tinge of yellow. The under parts are whitish, turning into salmon-pink on the tail. This beautiful newt reaches about 6 inches in length and has a very moist, slimy skin, which, combined with the lively motions of the creature, make it as slippery as an eel. It is found in the Alleghany range, from New York to Alabama.
Specimens which I am keeping prefer the wettest part of the cage, where they lie concealed in the moss and mud, leaving their hiding-places at night in search of insects. One of them escaped into the greenhouse and was discovered after nine months, having established its permanent home in a cleft between mossy stones: when the sweepings of a butterfly-net are emptied near its hiding-place it peeps out and with a flash of its long, forked, white-coloured tongue it secures its prey. Occasionally it goes into a tank, when it swims with rapid, undulating motions, the limbs being laid back and remaining inactive; it sometimes rises to the surface to emit and to take in air, but, although mostly resting half in the water, upon a rotten stump, it often lies for hours at the bottom without stirring. When kept in dry surroundings, the skin soon dries and wrinkles, and the animals show every sign of suffocation and general discomfort. The respiration of this lungless species by means of rapid movements of the throat is very limited, most of the necessary oxidisation of the blood being effected through the skin.
S. fuscus.–This, the only European species, is thoroughly terrestrial. It is found in the mountains bordering the Gulf of Genoa, and in Sardinia. Its total length remains under four inches. The smooth, very delicate and easily broken skin is brown above, light below, and speckled with lighter and darker markings. Below each nostril is a slight swelling, the remnant of the cirri or balancers common to the young of many species. It lives in shady surroundings, under stones, in old trees and in limestone-caves, glued to the walls with spread-out toes, belly and tail, quietly waiting for insects and spiders which it catches by flashing out the long tongue.
According to J. Berg,[[50]] it keeps well in cool, moist and well-ventilated places. It lives on flies, small beetles, and maggots; ants are also taken at once, probably owing to their lively movements, but a few minutes later the newts roll about in spasms and soon die. Towards the end of March one of Berg's specimens gave birth to four young, which were 36 mm., or nearly 1½ inches long, and differed from the adult only by their exceptionally large nostrils, thereby resembling the Mexican Thorius. The little ones shot out their tongues about 10 mm., feeding on Aphides.
Fig. 20.–Spelerpes fuscus, showing the position and shape of the partly and fully protruded tongue. The figure on the right side shows the tongue and the skeleton of the hyoid apparatus. B, the threadlike, elongated, first branchial arch; H, hyoid, in reality attached by its outer end to the vicinity of the quadrate; T, tongue. About × 2. (After Berg and Wiedersheim.)
Manculus.–The two species of this genus live in Carolina and Florida. M. quadridigitatus is a very slender, graceful little animal, about 3 inches in length, the long and thin tail being considerably larger than the rest of the body. Yellowish, minutely speckled with brown above and on the sides, greyish-white below. Life entirely terrestrial.