SUMMARY.Weekly skim‐net samples of chironomid pupal exuviae were collected at a single station on the River Chew, Avon, England, from September 1972 to September 1973. Eighty‐six types of exuviae were characterized in this study, of which sixty‐four made up only 4% of the year's catch. Thirty ‐eight percent of the year's catch was referable toMicropsectra atrofasciataKieffer.The samples showed the expected maxima of numbers and species in spring and early summer. The emergence periods for many of the more common species were very extended, with one or mor