DRIFT EMERGENCE TRAPS FOR THE RECORDING O F HATCHING RUNNING WATER INSECTS (EPHEMEROPTERA, PLECOPTERA, TRICHOPTERA, DIPTERA)

Almost all hitherto traps designed for recording the emergence of runn ing waters not only catch in various proportions emerging insects drif ted in from above but also such who directly emerge from the benthal r egion covered over by the trap. This also holds true for the Illies' e mergence-house. -Hence, a new constructed device is offered which proh ibits mixed catches of undefinable origin but exclusively takes in dri ft-emergence from an upper water layer of determinable thickness. An e ssential part of this device is a sieve-like plate which shields its i nterior from the benthal, but also can with its one end be let into th e water body at determinable depths by changing its angle of inclinati on in relation to the water surface. From the hereby given width of th e inflow opening and the speed of the water current the amount of wate r flow per time unit is to be calculated, thus giving a reference base for the qualitative and quantitative evaluation of the corresponding sample. There are 3 different versions of the new design which can be applied according to location, size and structure of the to be investi gated running-water, and for basic research as well as for longtime mo nitoring of water pollution and environmental assessments.