Nocturnal Flight Periodicity of caddisflies (Trichoptera) Along the Lake Huron Shoreline of Drummond Island, Michigan (USA)

Over 7000 caddisfly specimens, representing 33 species in 10 families, were collected between sunset and sunrise on 12 nights: three nights each during early July and early August in both 2023 and 2024. Collections were made on the southwestern side of Drummond Island along the shoreline of Lake Huron. Sampling occurred for five minutes at 15-minute intervals from near sunset (21:00) to 01:00 and then once again at 03:00 and 05:00. Nocturnal flight periodicity was broadly similar between years and months, with mean caddisfly abundance and species richness peaking at about one hour after sunset. Mean species accumulation varied between months and years with 63–78% of all caddisfly species collected within one hour after sunset and 80–95% within two hours. Similarly, the time required to collect 100% of all caddisfly species during a single month varied from three hours in July 2023 to 7.5 hours in July 2024. Our results indicate that sampling caddisflies for the first two hours after sunset will collect most species present, but sampling during multiple months and years as well as throughout the night is likely needed to collect nearly all species present. Our data on the nocturnal flight periodicity of lentic caddisflies is fundamentally similar to that for lotic caddisflies from previously published studies.