Genus Toxorhynchites Theobald, 1901

Type species: 
Classification: 

Subfamily Culicinae, tribe Toxorhynchitini. Toxorhynchites is the only genus of tribe Toxorhynchitini. It includes 90 currently recognised species in four subgenera: Afrorhynchus (19 species), Ankylorhynchus (4 species), Lynchiella (16 species) and Toxorhynchites (51 species). Genus abbreviation – Tx.

Characteristics: 

Toxorhynchites includes the largest mosquitoes. Adults are easily recognised by their large size and strongly bent proboscis. The body is covered with brightly coloured iridescent scales and the posterior abdominal segments have lateral scale-tufts. The scutellum is evenly rounded (as in Anopheles and Bironella) and the posterior margin of the wing is distinctly emarginated opposite the termination of vein CuA. Larvae are very large and easily recognized. They vary from pink to red and purple in colour, and possess modified mouth brushes comprised of 10 or fewer thick, flattened filaments for grasping prey. The abdominal setae occur in groups of three to five on common sclerites and a comb and pecten are both absent. Species of Toxorhynchites are remarkably similar in all life stages throughout the world and are difficult to identify. See Toxorhynchitini.

Phylogenetic relationships: 

Toxorhynchites was traditionally placed in a separate subfamily of Culicidae. Belkin (1962) believed that this over-emphasised the peculiar developments found in species of the genus and regarded it as constituting one of twelve tribes of 'true mosquitoes'. He was convinced that most of the distinctive features of Toxorhynchites are secondary adaptive characters relating to the large size and feeding habits of the adults and larvae. Members of the genus share the un-lobed condition of the scutellum and the presence of a precubital furrow on the wing with Anopheles and Bironella, characters considered to be symplesiomorphic by Colless (1979). Harbach (1977) discussed possible steps in the evolution of feeding behaviour in mosquito larvae and postulated that Toxorhynchites and the Anophelinae were derived from an early common ancestor of the Culicidae. In many respects, the adults resemble sabethine mosquitoes in overall ornamentation, reduction of thoracic chaetotaxy, lack of scales on the alula and upper calypter, and structures of the male genitalia. Based on characteristics of the larval labiohypopharynx, Harbach (1978) hypothesised that Toxorhynchites was derived from a sabethine ancestor. Features of larvae, including the absence of a comb and placement of setae on common tubercles, are paralleled in certain sabethines, e.g. Trichoprosopon. The lateral abdominal setae of some Eretmapodites larvae, as well as those of Armigeres (Leicesteria) dolichocephalus, are also borne on conspicuous common tubercles. Toxorhynchites also share with Sabethini the absence of a tracheoid area at the base of the trumpet, the position of setae 2,3-CT and the absence of setae at the apex of the paddle. Belkin believed that the similarities between Toxorhynchites and sabethines were indicative of a close relationship rather than the result of convergence. Whereas Toxorhynchites was paired with Culiseta in the implied weighting analysis of Harbach & Kitching (1998) based on morphological data, it was recovered as the sister of Sabethini when all characters in their data set were equally weighted or analysed using successive approximations character weighting. See Steffan & Evenhuis (1985) and Ribeiro (2004) for discussions of similarities and postulated affinities with other Culicidae.

Bionomics and disease relations: 

Toxorhynchites are basically forest mosquitoes. The larval habitats are mainly tree holes and bamboo, but a few species are found in leaf axils, pitcher plants, rock pools and artificial containers. The larvae of all species are predacious. They feed mainly on the larvae of other mosquito species, but exhibit cannibalism or feed on detritus in the absence of suitable prey. Males and females both feed exclusively on nectar and other sugary substances. The adults are active during the day. See Steffan & Evenhuis (1981) and Collins & Blackwell (2000) for details of Toxorhynchites biology.

Species of Toxorhynchites are not involved in the transmission of human or animal pathogens. The larvae of a few species have been used with some success to control economically important mosquitoes whose larvae inhabit plant cavities and artificial containers.

Distribution: 

Species of Toxorhynchites are largely confined to tropical regions. A few species occur in the eastern fringes of Asia and North America. Three apparently introduced species are found in Fiji and Samoa in the South Pacific, but species of the genus are otherwise absent from all oceanic islands, including New Zealand. Species of subgenus Toxorhynchites occur only in the Old World, those of subgenus Afrorhynchus occur in Africa, and species of subgenera Ankylorhynchus and Lynchiella are confined to the New World.

Principal references: 

Barraud, 1934 (as Megarhinus, south-central Asia); Edwards, 1941 (as Megarhinus, Afrotropical Region, adults); Hopkins, 1952 (Afrotropical Region, larvae); Lane, 1953 (Neotropical Region); Thurman, 1959b (Thailand); Belkin, 1962 (South Pacific, taxonomy); Forattini, 1965 (Neotropical Region); Cova-Garcia et al., 1966 (Venezuela); Belkin et al., 1970 (New World); Tanaka et al., 1979 (Japan); Steffan et al., 1980 (annotated bibliography); Steffan & Evenhuis, 1981 (biology); Clark-Gil & Darsie, 1983 (Guatemala, keys); Darsie, 1985 (Argentina, keys); Steffan & Evenhuis, 1985 (subgenus Toxorhynchites); Evenhuis & Steffan, 1986 (Acaudatus Group, Oriental Region); Lee et al., 1988 (subgenus Toxorhynchites, Australasian Region); Service, 1990 (Afrotropical Region); Ribeiro, 1991 (Afrotropical Region, Brevipalpis Group); Ribeiro, 1992 (subgenus Afrorhynchus); Collins & Blackwell, 2000 (biology); Ribeiro, 2004 (Madagascar, subgenus Afrorhynchus); Tyagi et al., 2015 (south central and south eastern Asia, key (adults, 24 species), bionomics, distribuitons, comparative morphology of species and subgenera).

Subgenera: 
Nomen dubium

aequatorianus Levi-Castillo, 1953

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith