Descriptions of the first larval instars of three Central European species of Hydaticus LEACH, H. transversalis (PONTOP.), H. seminiger (DEG.) and H. stagnalis (FABR.), are given, together with bionomical data and identification key to all larval stages. The larvae differ chiefly in their head shape, the form of clypeus and cephalic appendages, as well as in the length of cerci.