Phylogeny and classification of the Psocodea, with particular reference to lice (Psocodea: Phthiraptera)

Apomorphies that have been proposed for the Psocodea, Psocoptera, Phthiraptera and superfamilial groups within the Phthiraptera are enumerated and evaluated. The Psocodea and Phthiraptera are considered to be holophyletic, but the sister group of the Phthiraptera lies within the Psocoptera. Within the Phthiraptera the Anoplura and Rhyncophthirina form a holophyletic group whose sister group is the Ischnocera, and the Amblycera is the sister group of this assemblage. The common ancestor of the Phthiraptera is suggested to have been parasitic, and all lice are believed to have evolved under environmental constraints similar to those operating today. On the evidence provided by host relationships the origin of the lice is dated as the Cretaceous, but the host of the ancestor of the order is not identified. The lice of marsupials in South America and Australia are not considered to comprise a holophyletic group.