Troctomorpha is one of the three major suborders of Psocodea (barklice, booklice, and parasitic lice), alongside Psocomorpha and Trogiomorpha. There are more than 30 families and 5,800 described species in Troctomorpha. The order includes parasitic lice, which are most closely related to the booklice family Liposcelididae.

Psocodea is a taxonomic group of insects comprising the bark lice, book lice and parasitic lice. It was formerly considered a superorder, but is now generally considered by entomologists as an order. Despite the greatly differing appearance of parasitic lice (Phthiraptera), they are believed to have evolved from within the former order Psocoptera, which contained the bark lice and book lice, now found to be paraphyletic. They are often regarded as the most primitive of the hemipteroids. Psocodea contains around 11,000 species, divided among four suborders and more than 70 families. They range in size from 1–10 millimetres (0.04–0.4 in) in length.