Phenology and Distribution of Caddisflies (Trichoptera) in Oak Creek, A High-desert Perennial Stream in Arizona

We collected 58 species of caddisflies representing 30 genera and 16 families during a 5-year period in Oak Creek, Coconino Co., Arizona. This is the largest number of species of caddisflies reported in any drainage in Arizona and includes >50% of species reported from the state. Species assemblages changed dramatically along the 767-m descent of Oak Creek over a 70-km distance. Discharge records suggest reduced winter and spring surges of water and increased embeddedness of the channel have caused changes in assemblages of caddisflies in Oak Creek over the past several decades. Increased numbers of hydroptilids, hydropsychids, and leptocerids have replaced limnephilids. We conducted a 2-year phenological study at monthly intervals at two sites separated by