Hystrichopsylla schefferi

Description

Hystrichopsylla schefferi, also known as the mountain beaver flea and giant mountain beaver flea, is a parasitic holarctic insect belonging to the order Siphonaptera, the "siphon-wingless" (fleas). The fully grown adult can measure as much as 0.5 inches (13 mm) in length, and it is the largest living flea in the world. It is native to the American Northwest. Though most members of the genus Hystrichopsylla are not strongly associated with any particular host animal and will generally parasitize insectivores and rodents, H. schefferi is monoxenously associated with the mountain beaver with which its range is coterminous. The fleas of the family Hystrichopsyllidae, along with the family Pulicidae, are the oldest of fleas in evolutionary history. H. schefferi can be distinguished from the very similar and closely related species Hystrichopsylla gigas dippiei by the number of spines in the pronotal comb, as H. g. dippiei has 36 and H. schefferi has 46.