Subfamily Culicinae, tribe Sabethini. Isostomyia includes only four species. Genus abbreviation – Is.
The adults of Isostomyia are distinguished from other members of Sabethini in the New World by the following combination of characters: dorsal head scales with weak to moderate green or blue reflections, proboscis distinctly longer than forefemur, scutal scales moderately broad to broad and flat, postpronotum without posterior setae, lower mesokatepisternal setae usually not extended above lower edge of mesepimeron and all tarsi completely dark. The larvae of Isostomyia differ from those of Johnbelkinia, Onirion, Shannoniana, Trichoprosopon and some Wyeomyia in having a transverse slit-like occipital foramen and a filamentous pecten on the siphon. They are distinguished from other New World sabethines by the presence of a maxillary claw. They also differ from otherwise very similar larvae of Runchomyia in having seta 3-X branched, and seta 6-S strongly developed, rigid and hooked at the tip. Campos & Zavortink (2010) showed, without mention, that seta 13-T is inserted on a common plate with setae 9–12-T in the larva of Isostomyia paranensis, a feature which was only previously known in species of Kimia and Trichoprosopon (Harbach et al., 2007). See Sabethini.
Isostomyia shares close affinities with other New World genera of Sabethini. It was recovered in a sister-group relationship with Runchomyia (Ctenogoeldia) in the morphology-based phylogenetic analysis of Judd (1996) and as the sister of Shannoniana in the morphology-based phylogenetic analyses of Harbach & Kitching (1998), Harbach & Peyton (2000) and Harbach et al. (2007). The phylogenetic relationships of the species of Isostomyia are unknown.
What little is known about the bionomics of Isostomyia is based on collections of Is. espini. The larvae of this species are found in the leaf axils of terrestrial plants (aroids). The adults are known to enter houses and to bite humans outdoors in domestic areas.
The bionomics of Isostomyia is largely unknown, but it is unlikely that the species are involved in the transmission of pathogens to humans.
Species of Isostomyia are only known to occur in the Neotropical Region.