Descriptions of flea larvae (Siphonaptera: Hystrichopsyllidae, Ctenophthalmidae, Leptopsyllidae) of the specific parasites of the mountain beaver (Rodentia: Aplodontidae) in North America

The larvae of the four species of primary flea parasites of the mountain beaver, Aplodontia rufa (Rafinesque), are described and illustrated for the first time, and a key to their identification is provided. The larva of Hystrichopsylla schefferi Chapin is very large, with a total body length of more than 10 mm in the late third instar. Its mandible, with a series of marginal teeth along a scoop-shaped tip, is characteristic of members of the formerly recognized subgenus Hystroceras. The larvae of Paratyphloceras oregonensis Ewing and Trichopsylloides oregonensis Ewing are very similar to one another, but the former is much larger, with a total body length of about 8 mm in the late third instar, compared with 5 mm for the latter. These two species can also be separated in all instars on the basis of the setation on the abdominal segments. The larva of Dolichopsyllus stylosus (Baker) is extraordinary. The mandible bears two enormous, tusklike setae on a swollen base, the hypopharynx is a spiny, trilobed structure without setae, and there are five processes on the labial palps instead of the four typical in other species.