EMERGENCE OF CADDISFLIES FROM THE MIDREACH OF A MOUNTAIN STREAM IN THE THURINGIAN FOREST (INSECTA, TRICHOPTERA)

Fifty-seven species of caddisflies were identified in samples taken over a 7-month period from a large emergence trap placed on the mid-reach of a forested mountain stream in the Thuringian Forest, East Germany, in 1984. A total of 4,673 specimens were obtained during the sampling period. The community was dominated by collectors and shredders (52 % and 35.6 % of biomass) indicating a high input of allochthonous organic material from the bank trees as well as from upper stretches of the stream. The emergence periods and patterns of the common species are described and compared. Some species showed significant departures from a balanced sex-ratio. An explanation is proposed to account for the general unpredictability of sex-ratios in emergence traps. Unusual emergence patterns of 5 species are discussed in detail.