The Trichoptera of St. Helen's Island, Montreal: I. The Species Present and Their Relative Abundance at Light

Abstract

AbstractSt. Helen's Island, the site of Trichoptera studies in 1964 and 1965, is described. The Trichoptera encountered are listed, and taxonomic notes given where appropriate. Catches from a light-trap operated nightly in each year provide information for the different species concerning: relative abundance, frequency and seasonal range of occurrence, pest status, and sex ratio. Of the 99 species recorded, eight were classified as pests (causing a nuisance at light), six having this status in both years; together these eight species made up 87.6% of the seasonal total in 1965. Between late May and late September 1965, when large numbers arrived at light (median nightly catch ca. 3 × 103), a nuisance occurred on about one third of nights. Excluding Psychomyia flavida, of which only females were taken at light, most species showed a slight preponderance of males, but sex ratios varied widely according to species, year and night of capture.