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

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Abstract
St. 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.