Emergence of Trichoptera from Trout Creek, Colorado, USA

A total of 21 species of adult Trichoptera were collected over two years with black-light trap and sweep-net from a site on Trout Creek, a mountain stream in northwestern Colorado. The adult flight period was from mid-June to early October. A total of 7863 organisms were collected over the two years representing 8 families, 16 genera, and 21 species. Two species (Lepidostoma moneka and Brachycentrus americanus) accounted for 81% of the total numbers of adults. Seasonal emergence patterns exhibited three peaks in both numbers of adults and numbers of species collected. The early summer group (mid-June to mid-July) was represented by 4 species comprising 5% of total numbers. The mid-summer group (mid-July to mid-August) of 10 species accounted for 90% of total numbers. The late summer-early fall group (mid-August to early October) of 7 species comprised 5% of the total numbers of adults. Three species (L. moneka, Wormaldia gabriella, Neotrichia okapa) are new records for Colorado. Sex ratios for abundant species ranged from 34% females (B. americanus) to over 65% females (Glossosoma ventrale). Season appeared to have no effect on sex ratios.