Seasonality, sex ratios and arrival pattern of some New Zealand caddis (Trichoptera) to Light‐Traps

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Abstract
We report the results of three independent light‐trapping studies of caddis (Trichoptera) at three widely‐separated stream‐side sites in New Zealand. A total of 66 caddis species in 10 families was recorded, as follows: 33 from site K (Kawarau Gorge) in 1990–91, 28 from site T (Turitea Stream) in 1986–87 and 45 from site W (Waitakere Stream/Cascade Stream) in 1967–68. Many of the species were captured in sufficient numbers to estimate their adult flight season. The results show that some species in the families Hydrobiosidae, Hydroptili‐dae and perhaps also Philopotamidae and Chathamiidae are present as adults during every month of the year. Species captured from 7 other families appeared to have a mid‐winter break with no active adults present. For some species there is a marked change in the sex ratio through the flight season from predominantly males early in the season to predominantly females at the end. For four common species at one site, the arrival pattern at the light trap was unimodal. It was highest shortly after sunset for three of the species; the fourth showed a peak in arrival rate four hours after sunset. Numbers of insects captured were strongly dependent on air temperature.