SECTION III 



KEY TO AQUATIC GENERA AND SPECIES OF ADULT DRYOPOID BEETLES 



OF THE UNITED STATES 



Compact, ovoid; head retracted within prothorax and invisible 

 from dorsal view, antennae fitting into grooves of 

 prosternum; tarsus with third segment lobed; claws not 

 prominent; not genuinely aquatic (Fig. 16): 



CHELONARIIDAE, Chelonarium leoontei 



Head usually visible from dorsal view, though it may be 



temporarily retracted within prothorax; third segment of 

 tarsus not conspicuously lobed; tarsal claws prominent .... 2 



Fig. 16- Chelonariim teaontei adult, dorsal. 



2(1) Typically hard-bodied; front coxae rounded or transverse 3 



Typically soft-bodied; front coxae exserted and projecting 



and/or hind margin or pronotum crenulate 5 



3(2) Typically very plump, convex, and ovoid; legs retractile; 



apical segment of tarsus shorter than remaining segments 

 combined; middle coxae widely separated, hind coxae close 



together LIMNICHIDAE 105 



Usually more elongate; legs not retractile; apical segment 

 of tarsus usually as long as other four segments combined, 

 with large claws; if middle coxae are widely separate, so 

 are hind coxae 4 



4(3) Anterior coxae typically globular and without exposed 



trochantin; antennae typically slender, not forming a 

 pectinate or lamellate club; female genitalia symmetrical, 

 with jointed, movable styli (Fig. 11); about 1-8 mm long, 



usually less than 4 mm . . . .ELMIDAE 6 



Anterior coxae transverse and with exposed trochantin; 



antennae usually short, with apical segments pectinate or 

 lamellate and forming a club; female genitalia without 

 styli, usually asymmetrical and resembling two knife 

 blades (Figs 101, 102), functioning as ovipositors; about 

 4-8 mm long ^.DRYOPIDAE 94 



25 



