An emergence trap was placed over a section of Six Mile Creek, a warm water stream which flows into Lake Erie and is located in Erie County, PA. Six families, 17 species, and 1782 specimens of caddisflies were collected over a three year period.Diplectrona modestaBanks, the most abundant species, has an extended emergence from late May to August‐September and may exist in two cohorts.Wormaldia moesta(Banks) was the next most abundant species; in the 1979 collection it was four times more abundant than during either of the previous two years. Two cohorts may also exist in this species, one emerging in spring, and the other in late summer.Neophylax concinnusMcLachlan, the third most abundant species, also revealed a dramatic increase in numbers the third year over the previous two years. This species always emerged during a period of four to six weeks in early autumn.Polycentropus elarusRoss, the next most abundant species, was quite synchronous in emergence in the last two years of the study.Dolophilodes distinctus (Walker) has shown a decline over the three year period with as many collected the first year as in the next two years combined. Four species of Rhyacophilidae were collected, all with increasing numbers each year.