Helichus, of the family Dryopidae, is unique among insects in that the 

 adults are aquatic, behaving rather like elmids, whereas the larvae are 

 terrestrial, inhabiting soil or decaying wood. The adults are not 

 permanently bound to the water once they return to it. They probably 

 emerge and fly at night, at least upon occasion. The females have sharp- 

 tipped ovipositors with which they probably insert their eggs into 

 appropriate materials. The larvae of Dryops and Pelonomus are also soil- 

 dwellers, the adults being terrestrial or, at most, riparian. Dvyops 

 frequents trash lodged in streams, but does not appear to enter the 

 water. 



