Morphological variation associated with function in three species in the family Pediculidae (Insecta: Phthiraptera)

The reliability of the characters used by taxonomists to separate species has always been in question. If the variation of a character is associated to its function, this feature may be crucial in segregating species. For this paper, 567 specimens of lice, (Pediculus humanus N=153, Anthropophthirus capitis N=223, Anthropophthirus pseudohumanus N=191) were measured. They were mounted on microscope slides to compare the possible variation of the leg structures involved in the adhesion to the substrate, in the species of lice related to man. We found that there is significant relationship between the structural variation of the claws of the tibio-tarsal complex and the diameter of the substrate they adhere to. This shows there is a strong pressure from the substrate on the claw's structure, this variation does not affect the width of the basitibia.