Gordioidea

Gordioidea is an order (sometimes placed at superfamily level) of parasitic horsehair worms. Its taxonomy remains uncertain, but appears to be contained in the monotypic class Gordioida and contains about 320 known species.

Biology
Gordioidean adults are free-living in freshwater or semi-terrestrial habitats and larvae parasitise insects, primarily Orthopterans. Unlike Nectonematoideans, which are marine, gordioideans lack lateral rows of setae and have a single, ventral epidermal cord and their blastocoel is filled with mesenchyme in young worms but become open when older.

Families and genera
The Integrated Taxonomic Information System lists the following genera in two families:

Chordodidae
Auth. May, 1919; selected genera:
 * Subfamily Chordodinae Heinze, 1935
 * Chordodes Creplin, 1847
 * Dacochordodes Capuse, 1965
 * Euchordodes Heinze, 1937
 * Neochordodes Carvalho, 1942
 * Pantachordodes Heinze, 1954
 * Spinochordodes Kirjanova, 1950
 * Subfamily Paragordiinae
 * Paragordius Camerano, 1897
 * incertae sedis
 * Gordionus Müller, 1927
 * Parachordodes Camerano, 1897
 * Paragordionus Heinze, 1935
 * Semigordionus Heinze, 1952

Gordiidae
Auth. May, 1919
 * Acutogordius Heinze, 1952
 * Gordius Linnaeus, 1758