Homalopsis Kuhl & Hasselt 1822

Homalopsis buccata ranges from northern Sumatra to Salanga Island, Indonesia and Borneo; it is present on the Malaysian peninsula and in extreme southern Thailand (vicinity of Pattani). There is a single specimen reported from Sulawesi, but its presence there has not been confirmed. Populations of Homalopsis that fall outside of this region belong to different species (Murphy et al. 2012). Therefore its distribution is primarily Indonesia and Malaysia. Homalopsis from Myanmar and possibly the Andaman Sea coast of Thailand are H. semizonata Blyth. Homalopsis from the Mekong Valley are H. nigroventralis Deuve. Homalopsis from the lowlands of Indochina and Thailand are H. mereljcoxi Murphy et al. 2012. Homalopsis hardwickii Gray is known from a single specimen with the type locality of "India" and a member of this genus has been reported from Nepal.

Homalopsis buccata ranges from northern Sumatra to Salanga Island, Indonesia and Borneo; it is present on the Malaysian peninsula and in extreme southern Thailand (vicinity of Pattani). There is a single specimen reported from Sulawesi, but its presence there has not been confirmed. Populations of Homalopsis that fall outside of this region belong to different species (Murphy et al. 2012). Therefore its distribution is primarily Indonesia and Malaysian. Homalopsis from Myanmar and possibly the Andaman Sea coast of Thailand are H. semizonata Blyth. Homalopsis from the Mekong Valley are H. nigroventralis Deuve. Homalopsis from the lowlands of Indochina and Thailand are H. mereljcoxi Murphy et al. 2012. Homalopsis hardwickii Gray is known from a single specimen with the type locality of "India" and a member of this genus has been reported from Nepal.

Masked water snakes of the genus Homalopsis are abundant in the low elevation wetlands of Southeast Asia. They are the largest members of the family Homalopsidae, exceeding 1.3 m in total length, with robust bodies, wide heads, usually a distinctive pattern of alternating brown and cream bands outlined in black, and usually a pale colored venter with paired dark spots on the lateral edge of the ventrals and first dorsal rows of scales. Masked water snakes are nocturnal ambush predators preying on small fish, and their large size and interesting dorsal pattern makes them a target for the novelty leather industry.

Currently, five species are recognized, H. buccata Linnaeus inhabits the Indonseian Archipelago and the adjacent mainald. Stuart et al. (2006) resurrected H. nigroventralis Deuve, aMekong drainage endemic with disjunct populations scattered in Loas, Thailand, Vietnam, and Cambodia. Murphy et al. (2012) revalidated H. hardwickii Gray a species known only from the type specimen and it lacks a type locality. The species is supected of inhabiting northeast India and possibly Nepal. They also revalidatedHomalopsis semizonataBlyth a species known from Kawkareik, Twante near Rangoon, and Mottama, Myanmar. This species may be more widespread than known specimens suggest. Its known distribution is centered on the Gulf of Martaban, but it may extend to the north following the Ayeyarwady River and to the south following the Andaman Sea’s coastal plain in southern Myanmar and along the Andaman coast of peninsular Thailand.The recently describe Homalopsis mereljcoxi is an Indochinese species and is exploited in the snake harvest at Tonle Sap, in Cambodia (Brooks et al. 2007).

Like all homalopsid snakes Homalopsis is viviaporus and females give birth to relatively large young.