DISPERSAL OF ADULT CADDISFLIES (TRICHOPTERA) INTO FORESTS ALONGSIDE 3NEW-ZEALAND STREAMS

The abundance and taxonomic richness of adult caddisfly faunas were de termined at varing distances (up to 200 m) away from three North Islan d, New Zealand, streams to help define appropriate forested riparian z one widths for adult aquatic insects. Adults were collected using stic ky traps and ultraviolet light traps on four occasions over summer. Li ght traps were more effective at catching caddisflies than sticky trap s, but both methods gave similar patterns of declining abundance and t axonomic richness with distance from the stream edge. Abundances of to tal caddisflies at 20 m were <21% of those caught at the stream edge f or both trapping techniques. The same trends were evident for abundanc es of most common species in light traps, whereas bimodal peaks were e vident with distance from the channel edge for percentage females of t hree common species. More than 30% of species caught at the stream edg e was found in light traps at least 70 m into forest at all sites. A f aster rate of decline for abundance than richness with distance away f rom the stream reflected the relatively large distances travelled by r epresentatives of many species. Similar results from the three sites f or numbers and species richness indicate that the main area of activit y for adult Trichoptera in forested riparian zones was within 30 m of the stream edge at these sites.