Abstract
Adult caddisflies were collected weekly from a spring-fed brook of Shimauchi-yusui from 11 April 2013 to 5 June 2014. A total of 11867 specimens belonging to 39 species, 18 genera and 14 families were identified. The most abundant species collected in 1 year (the first 52 weeks) were Agapetus sibiricus Martynov 1918 (60%), Apatania aberrans (Martynov 1933) (12%) and Micrasema spinosum Nozaki and Tanida 2007 (5.4%). The Trichoptera fauna mainly reflected the major larval habitats of this brook, but other factors such as water temperature also probably affect species composition. The most common species (wherein more than 50 individuals were collected) had discrete seasonal flight periods.