Helidiaptomus is a copepod genus distinguished by a single eye spot. Although it bears a resemblance in size and appearance to Cyclops, it is notably characterized by extremely long first antennae that extend beyond the length of its body. It is commonly found in larger freshwater ponds, lakes, and calm waters. Unlike Cyclops, females of Heliaptomus carry their eggs in a single sac rather than the twin sacs.