ABSTRACT
Sphaerularioid nematode parasites in the body cavity of insects are represented by 208 species distributed in 29 genera and 6 families excluding phoretic nematodes. Six genera of Sphaerularioids are monospecific and 10 genera have 2–5 species. The complex host-parasite relationships of Sphaerularioids remain little known. Survival and perpetuation of the nematode is insured by the annual rate of parasitism, the host’s fecundity reduction, the dissemination of juvenile nematodes by living adult insects, the adaptation of the length of the free-living period of infective females, and the synchronization with the host larval development period. Iotonchiidae also have a primary heterosexual generation alternating with a secondary parthenogenetic generation, but they have a characteristic morphology which may indicate a different phylogenetic origin. Sphaerulariidae have hypertrophied or everted uterus and a single heterosexual generation cycle similar to that of Allantonematidae. Members of the Fergusobiidae and Phaenopsitylenchidae present both parasitic and free-living generations.
