Évolution journalière de la dérive des exuvies nymphales de Chironomidae ( Diptera) dans une rivière salmonicole (le Samson, Belgique).

Pupal exuviae of chironomids were collected in the river Samson by means of a drift net, over a period of 24 hours in September 1993. 50 species were identified, 14 of which are new to Belgium. The incidence of the exuviae of different species changed during the course of the 24 hours: exuviae of 33 species were caught at sunset, 14 at the beginning of the afternoon. The diel periodicity of emergence of 9 abundant species was studied by collecting their pupal exuviae.