Bothriechis

Species that belong to the genus Bothriechis typically reach a total length (tail included) of 60-80 cm (24-31 in), while B. aurifer, B. bicolor and B. lateralis are known to grow to a total length of 1 m (39 in) or more.

General characteristics include a sharply defined canthus rostralis, an unelevated snout, a rostral scale that is not as high as it is broad, and a prehensile tail that accounts for at least 15% of the body length.

The color pattern usually consists of a green ground color that may or may not include pale or dark markings. B. schlegelii is an exception to this rule.

Bothriechis species occur in southern Mexico (southeastern Oaxaca and the northern highlands of Chiapas), through Central America to northern South America (Colombia, western Venezuela, Ecuador and northern Peru).

As a general rule, species of Bothriechis found above 1,500 m (4,900 ft) altitude tend to be diurnal, while those found below 1,000 m (3,300 ft) tend to be active at night. Those found between 1,000 and 1,500 m (3,300 and 4,900 ft) may be active at any time of the day.

Bothriechis venom is primarily a haemotoxin which causes severe pain, swelling, bleb formation, bruising, and quite often necrosis. If untreated it can lead to loss of a limb, or even death. Each year several farmers and plantation workers are bitten by eyelash vipers, sometimes resulting in fatalities. Wyeth in the United States and Instituto Clodomiro Picado in Costa Rica both manufacture different polyvalent antivenins which can be used to treat eyelash viper envenomations.

There are 19 recognized species.

^T type species

A new species of Bothriechis from Guatemala and Honduras, B. thalassinus, was described by Campbell & E.N. Smith (2000). Campbell & Lamar (2004) recognize this species, as well as a ninth addition to the genus: B. supraciliaris, which was first described by Taylor (1954) as a subspecies of B. schlegelii, and is found in southwestern Costa Rica.

In 2024, a systematic revision of B. schlegelii through DNA-sequencing split it into an additional number of species: B. klebbai, B. rasikusumorum, B. khwargi, B. rahimi, and B. hussaini. At the same time names that were previously synonyms were revalidated: B. nigroadspersus (Steindachner, 1870), B. nitidus (Günther, 1859), and B. torvus (Posada Arango, 1889a). Due to the close relation between these species alongside B. supraciliaris, they are considered to be part of a B. schlegelii species complex, otherwise referred to as the "eyelash clade" within Bothriechis. These "eyelash vipers" form a monophyletic clade that is sister to the rest of the genus.

B. guifarroi was discovered in 2010 and described by Townsend et al. in 2013, in a study that included the following suggested phylogenetic tree of the genus: