Ahaetulla

"Ahaetulla," commonly referred to as Asian vine snakes or Asian whip snakes, is a genus of colubrid snakes distributed throughout tropical Asia. They are considered by some scientists to be mildly venomous and are what is commonly termed as 'rear-fanged' or more appropriately, opisthoglyphous, meaning their enlarged teeth or fangs, intended to aid in venom delivery, are located in the back of the upper jaw, instead of in the front as they are in vipers or cobras. As colubrids, Ahaetulla do not possess a true venom gland or a sophisticated venom delivery system. The Duvernoy's gland of this genus, homologous to the venom gland of true venomous snakes, produces a secretion which, though not well studied, is considered not to be medically significant to humans. 
Green-colored members of this genus are often referred to as green vine snakes. They are not to be confused with the "green vine snake" "Oxybelis fulgidus", which convergently appears very similar but is found in Central and South America. 
Taxonomy.
Their closest relative is the monotypic genus "Proahaetulla", which "Ahaetulla" diverged from in the mid-Oligocene. From here, the clade containing "Proahaetulla" and "Ahaetulla" is a sister group to the genus "Dryophiops", and the clade containing all three of these genera is a sister group to the clade containing the bronzeback snakes ("Dendrelaphis") and flying snakes ("Chrysopelea"). 
In 2020, an analysis of "Ahaetulla nasuta, Ahaetulla dispar", and "Ahaetulla pulverulenta" throughout their range found them to represent species complexes containing several undescribed or formerly synonymized species, leading to the description of "A. borealis", "A. farnsworthi", "A. malabarica", "A. travancorica", and "A. sahyadrensis", as well as the resurrection of "A. oxyrhyncha" and "A. isabellina". "Ahaetulla nasuta" and "Ahaetulla pulverulenta", formerly considered to have much wider ranges, are now considered endemic to Sri Lanka. 
Geographic range.
They are found from Sri Lanka and India to China and much of Southeast Asia. Sri Lanka and the Western Ghats of India are major hotspots of diversity for the genus, with 10 of the 17 currently-described species being endemic to these regions.
Species.
The taxonomy of vine snakes is not well-documented, and literature varies widely, but there are 17 currently accepted species in the genus "Ahaetulla":
Several undescribed species (including the Southeast Asian "Ahaetulla" formerly assigned to "A. nasuta") still likely remain in these complexes
Description.
All "Ahaetulla" species are characterized by thin, elongated bodies, with extremely long tails and a sharply triangular shaped head. They are primarily green in color, but can vary quite a bit to yellows, oranges, greys, and browns. They can have black and/or white patterning, or can be solid in color. Their eyes are almost unique in the reptile world, having keen binocular vision and keyhole shaped pupils, being similar in this aspect with twig snakes, who also have keyhole shaped pupils.
Etymology.
The genus name "Ahaetulla" comes from the Sinhalese name "ehetulla" for "Ahaetulla nasuta", which means 'eye plucker' or 'eye striker.
Vernacular names.
The sinhala name "Aheatulla" or "eye-plucker" forms the taxonomic genus name. In Tamil, it is known as pachai paambu, in Malayalam it is known as pachila paambu, in Telugu it is known as "Pasarika Paamu", in Marathi, it is known as shelati snake, and in Kannada it is known as Hasiru Haavu. There are dozens of other vernacular names for this snake genus within its range.
Behavior.
They are primarily diurnal and arboreal, living in humid rainforests. Their diet consists mainly of lizards, but sometimes frogs and rodents are also consumed. "Ahaetulla fronticincta", however, feeds exclusively on fish, striking its prey from branches overhanging water. "Ahaetulla" venom is not considered to be dangerous to humans, but serves to cause paralysis in their fast moving prey choices. They are ovoviviparous.
In captivity.
"Ahaetulla" species are not yet frequently captive bred, as are many of the more popular snakes in the reptile keeping hobby. They are suitable for more advanced keepers, requiring a humid arboreal habitat and a diet of lizards as they rarely switch to rodents. Without proper husbandry, they are prone to health issues and stress.