The ten or more species of _Trimeresurus_ occupy their place in the woodland districts of tropical Asia and its islands. In them the hinder labial shields are the smallest. The head is triangular, covered above with small scales, except the foremost part of the snout and the superciliary region, which generally are shielded; body with more or less distinctly keeled scales, in from seventeen to twenty-five series. Body and tail of moderate length, prehensile. These reptiles are more or less arboreal, as is indicated by their prehensile tail, and by their green or varied coloration. "In general," remarks Dr. Günther, "they are sluggish, not attempting to move out of the way, and as they very closely resemble the branch on which they rest, they are frequently not perceived until they prepare to dart, vibrating the tail, and uttering a faint hissing sound, or until they have struck the disturber of their rest. Accidents caused by them, therefore, are not of uncommon occurrence, and it is a fortunate circumstance that comparatively few of them attain to a size of more than two feet, so that the consequences of their bite are less to be dreaded than that of various other poisonous Snakes. Indeed, numerous cases are on record which show that the symptoms indicating a general effect on the system were of short duration, extending only over from two to forty-eight hours, and confined to vomiting, retching, and fever. After the pain and swelling of the bitten member or spot have subsided, the vicinity round the wound becomes discoloured, mortifies, and is finally thrown off as a black, circular slough, after which health is speedily restored. The bite of larger specimens, from two to three feet long, is more dangerous, and has occasionally proved fatal; so that the greatest care should always be observed in the immediate treatment of the patient. When roused, these Snakes are extremely fierce, striking at everything within their reach; and Cantor states that in the extreme of fury they will fix their fangs in their own bodies. Frogs, small mammalia, and birds form their food, and I have never found a Lizard or Snake in their stomach."