Observations on the biology of Romanomermis sp. (Nematoda: Mermithidae) parasites of Aedes in western Wyoming.

Univoltine Aedes mosquito larvae infected by Romanomermis sp. were found at 2 localities in Yellowstone National Park, Wyoming. Aedes nevadensis, Ae. impiger, Ae. pullatus and Ae. punctor were the predominant host species. Only Ae. nevadensis was common to all sites. Rates of parasitism ranged from 55 to 93% and differed significantly between localities. Significant annual variation in the rate of parasitism occurred within populations, but neither infection rate nor mean parasite load differed among host species. Parasite populations were distributed among host species in proportion to abundance, but distributions of parasites within host species were over-dispersed. Inter-specific variation in survival of infected larvae was associated with the degree to which immune responses were manifested in different host species.