Composition and flight periodicity of adult caddisflies in New Zealand hill‐country catchments of contrasting land use

Abstract

A total of 6085 adult Trichoptera (excluding Hydroptilidae) representing 12 families, 31 genera, and 56 species were collected by a combination of Malaise net and light trapping from July 1998 to July 1999 at three hill‐country sites of contrasting catchment land use (100% native forest, a pasture site with native forest headwaters, and 100% pasture) in the Waikato, northern New Zealand. Forty‐eight species of Trichoptera were collected from Malaise nets and 45 species from light traps. Eleven species of Trichoptera were only ever collected from the Malaise nets and seven species from only the light traps. At the native forest site, Malaise nets collected more species and taxa of conservation interest than did light traps, possibly reflecting diurnal activity or non‐attraction to light by some species. Several species of Trichoptera showed site specificity and most of these were found at the native forest site. Twenty‐eight species were active for at least 6 months of the year with at least four species active all year. A minimum overnight air temperature of at least 9°C was required to induce Trichoptera flight activity, but large‐scale flight activity may require temperatures greater than 14°C. Trichoptera with free‐living and net spinning larvae exhibited extended flight periods, and for three species examined there were bi‐modal activity peaks. Adult caddisflies with cased larvae which grazed on epilithic food resources generally had reduced flight periods and one species had a well‐defined, synchronous periodicity. These findings suggest flight periodicity may partly be a functional response to larval food availability.