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Trichodectidae (order Phthiraptera, suborder Ischnocera) Family of chewing lice which are parasitic on placental mammals. Members of the family are distinguished from other Ischnocera by the presence of only one antennal flagellomere in all males and most females, two or more hook-like setae on the antennal flagellum of most males, lateral abdominal tergal pits in males, and only one tarsal claw on each leg. Trichodectes canis (dog louse) transmits tapeworms between dogs but otherwise members of the family are not known to be vectors of disease. Trichodectidae parasitic on sheep, goats, cattle, and dogs cause irritation by their biting, and the efforts of the host to dislodge them can lead to loss of hair. There are 20 genera, with about 350 species, distributed world-wide.