The larva and pupa of Eurycnemus crassipes (Panzer) are described for the first time. Larval and pupal diagnoses are given for the genus Eurycnemus van der Wulp. — E. crassipes is found in lotic waters where they may be associated with Hydropsyche pellucidula or H. siltalai (Trichoptera). The species appears to be univoltine with main emergence between late June and beginning of September. The species is known from Europe while the genus is reported from the Holarctic Region.