Ecology of TwoProsimuliumSpecies (Diptera) with Reference to their Ovarian Cycles

Abstract

Prosimulium fuscumSyme and Davies,P. mixtumS. and D. andP. fontanumS. and D. form a complex of closely-related and largely sympatric species formerly known in North America (Twinn, 1936; Stone and Jamnback, 1955) under the single nameP. hirtipesFries, a well known species in the northern Palaearctic. The first step in demonstrating the multiple nature of the forms grouped under this name in North America was taken by Rothfels (1956) who showed by study of rhe larval salivary gland chromosomes that at least three non-interbreeding forms were present in eastern Canada. L. Davies (1957a) concluded from a study of specimens of all life-stages that none of the North American forms agreed with EuropeanP. hirtipes. A further step in the process was afforded by the work of Syme and D. M. Davies (1958), which erected the three species named above as a result of anatomical study of cytologically defined material, and showed that adult females ofP. fuscumandP. mixtumcould be reliably separated, mainly by features of the genitalia. The present work may be considered as a further step in the study of the commonProsimuliumof eastern North America, by providing information on their ecology, thus amplifying the cytological and anatomical conclusions arrived at in the papers cited above.