This is a somewhat heterogeneous group, most of whose members are characterized by clubbed feelers and simple, unbroadened tarsal segments - usually five on each foot - but in some familie andenera the males have less than the normal number on the feet of one pair.
The bestknown family is the Hydrophilidae, in which the feelers are short with less than eleven segments and the maxillary palpi very long.
Side, being scooped in bubbles by the terminal segments of the feelers when the insect rises to the surface.
2 b, 9b and 26 b, c); the number of segments is usually eleven, but may vary from two to more than twenty.
1, A) are of the usual insectan type, but in many families one, two, or even three of the five foot-segments may be reduced or absent.