We document 134 caddisfly species and their seasonal and habitat affinities based on 93 samples collected from 26 sites throughout the Manistee River watershed in the lower peninsula of Michigan from May through September, 2010. Eleven of these species: Banksiola dossuaria (Say), Cheumatopsyche aphanta Ross, Cheumatopsyche pasella Ross, Hydroptila xera Ross, Ironoquia lyrata (Ross), Lepidostoma vernale (Banks), Neotrichia vibrans Ross, Nyctiophylax affinis (Banks), Oxyethira aeola Ross, Oxyethira rivicola Blickle and Morse, and Polycentropus timesis (Denning) are reported from Michigan for the first time. More than 85% of species reached peak adult abundance during June or July, although a few species reached peak abundance or emerged exclusively during the other months. Overall species richness reached its peak during early July, with a smaller peak of unique species in September. Caddisfly faunas in lakes, small streams, medium rivers, and large rivers were all distinct from each other, suggesting that the overall watershed is following patterns predicted by the River Continuum Concept. It is likely that the Michigan caddisfly fauna contains considerably more species than what is currently known
