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

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.

Emergence Trap Collections of Trichoptera From an Oregon Stream

“…Figure 4 shows the cumulative emergence of both males and females of six common species. The analysis of nightly sex ratios of caddisflies collected at light traps by Corbet et al (1966) revealed no consistent changes correlated with the time of year that would indicate whether either sex had an earlier emergence period. penitum are mean rates for the 3 years but only for the autumn emergence, as the start of the spring emergence was not collected in 1968.…”

“…It is apparent that results from light trap collections are largely a measure of activity and that the sex ratio from specimens collected by this method is not necessarily that existing at emergence (Crichton 1960;Corbet et al 1966;Ulfstrand 1970). It is apparent that results from light trap collections are largely a measure of activity and that the sex ratio from specimens collected by this method is not necessarily that existing at emergence (Crichton 1960;Corbet et al 1966;Ulfstrand 1970).…”

The Temporary Abatement of Nuisance Species of Trichoptera With DDD (Tde) Larvicide

“…The mean (arithmetic) catch volume of 74 nll per evening throughout 1967 (Table VIII) is substantially lower than the threshold value of 100 rnl that was reported by Corbet et al (1966) to indicate a local density of flying insects capable of creating a nuisance to man, and indicates that in general the objective of the larviciding program was attained. This also was the general opinion of members of our staff and certain employees of Expo 67 who made personal observations almost every day and evening throughout the summer of 1967 and noted that shadfly accumulations were rarely seen on the site.…”

“…1 and has been described by Corbet et al ( 1966) andFredeen ( 1969). 1 and has been described by Corbet et al ( 1966) andFredeen ( 1969).…”

The Abatement of Nuisance Species of Trichoptera With DDT Applied to the Resting Sites of Adults

“…These differences were not entirely due to different collecting methods even though at St. Helen's Island the Trichoptera were collected in a very effective light trap consisting of a 125-w mercury-vapor lamp in a metal cone over a bucket of alcohol (Corbet et al 1966) whereas at Fort Erie they were collected in emergence cages and with sweep nets through swarms and shrubbery, and around incandescent lights at night (E. G. Munroe, pers. These differences were not entirely due to different collecting methods even though at St. Helen's Island the Trichoptera were collected in a very effective light trap consisting of a 125-w mercury-vapor lamp in a metal cone over a bucket of alcohol (Corbet et al 1966) whereas at Fort Erie they were collected in emergence cages and with sweep nets through swarms and shrubbery, and around incandescent lights at night (E. G. Munroe, pers.…”