Of ten species of snakes that ascend trees in Ceylon to search for squirrels and lizards, and to rifle the nests of birds, one half, including the green carawala, and the deadly tic polonga, are believed by the natives to be venomous; but the truth of this is very dubious. I have heard of the cobra being found on the crown of a coco-nut palm, attracted, it was said, by the toddy which was flowing at the time, it being the season for drawing it. Surrounding Elie House, near Colombo, in which I resided, were a number of tall casuarinas and India-rubber trees, whose branches almost touched the lattices of the window of the room in which I usually sat. These were a favourite resort of the tree-snakes, and in the early morning the numbers which clung to them were sometimes quite remarkable. I had thus an opportunity of observing the action of these creatures, which seems to me one of vigilance rather than of effort, the tongue being in perpetual activity, as if it were an organ of feeling; and in those in which the nose is elongated, a similar mobility and restlessness, especially when alarmed, affords evidence of the same faculty.
The general characteristic of the Tree-snake is an exceedingly thin and delicate body, often adorned with colours exquisite as those of the foliage amongst which they live concealed. In some of the South American species the tints vie in brilliancy with those of the humming-birds; whilst their forms are so flexible and slender as to justify the name conferred on them of "whip-snakes." The Siamese, to denote these combinations of grace and splendour, call them "Sun-beams." A naturalist[3061], describing a bright green species in Brazil (Philodryas viridissimus), writes: "I am always delighted when I find that another tree-snake has settled in my garden. You look for a bird's nest, the young ones have gone, but you find their bed occupied by one of these beautiful creatures, which will coil up its body of two feet in length within a space no larger than the hollow of your hand. They appear to be always watchful; for at the instant you discover one, the quick playing of the long, black, forked tongue will show you that you too are observed. On perceiving the slightest sign of your intention to disturb it, the snake will dart upwards through the branches and over the leaves which scarcely appear to bend beneath the weight. A moment more, and you have lost sight of it. Whenever I return to Europe, you may be sure that in my hot-house those harmless, lovely creatures shall not be missing."
Ceylon has several species of Tree-snakes, and one of the most common is the green Passerita, easily recognized from its bright colour and from the pointed moveable appendage, into which the snout is prolonged. The snakes of this genus being active chiefly during the night, the pupil of the eye is linear and horizontal. They never willingly descend from trees, but prey there upon nocturnal Saurians, geckoes, small birds and their young; and they are perfectly harmless, although they often try to bite. It is strange that none of the numerous specimens which it has been attempted to bring to Europe have ever fed in captivity; whilst in South America they take their food freely in confinement, provided that some green plants are placed in their cage.
In Ceylon I have never seen any specimen of a larger size than three feet; whilst they are known to attain to more than five on the Indian Continent.
The inference is obvious, that the green coloration of the majority of tree-snakes has more or less connection with their habits and mode of life. Indeed, whenever a green-coloured snake is observed, it may at once be pronounced, if slender or provided with a prehensile tail, to be of the kind which passes its life on trees; but if it be short-bodied then it lives on the prairies. There are nevertheless tree-snakes which have a very different coloration; and one of the most remarkable species is the Passerita fusca or Dryinus fuscus, of which a figure is annexed. It closely resembles the green Passerita in form, so that naturalists have considered it to be a mere variety. It is entirely of a shining brown, shot with purple, and the yellow longitudinal stripe which runs along the side of the belly of the green species, is absent in this one. It is much more rare than the green one, and does not appear to be found in Hindostan: no intermediate forms have been observed in Ceylon.
Water-Snakes.—The fresh-water snakes, of which several species[3081] inhabit the still waters and pools, are all harmless in Ceylon. A gentleman, who found near a river an agglutinated cluster of the eggs of one variety (Tropidophis schistosus), placed them under a glass shade on his drawing-room table, where one by one the young reptiles emerged from the shell to the number of twenty.
The sea-snakes of the Indian tropics did not escape the notice of the early Greek mariners who navigated those seas; and amongst the facts collected by them, Ælian has briefly recorded that the Indian Ocean produces serpents with flattened tails[3082], whose bite, he adds, is to be dreaded less for its venom than the laceration of its teeth. The first statement is accurate, but the latter is incorrect, as there is an all but unanimous concurrence of opinion that every species of this family of serpents is more or less poisonous. The compression of the tail noticed by Ælian is one of the principal characteristics of these reptiles, as their motion through the water is mainly effected by its aid, coupled with the undulating movement of the rest of the body. Their scales, instead of being imbricated like those of land-snakes, form hexagons; and those on the belly, instead of being scutate and enlarged, are nearly of the same size and form as on other parts of the body.