356 



Leech and Chandler: Coleoptera 



together of the terminal segments of the pectinate 

 club. 



species. Proc. Ent. Soc. Wash., 37:137-145, incl 

 pi. No. 17. 



Key to Nearctic Genera of Dryopldae 

 Adults 



Family ELMIDAE 



Riffle Beetles 



1. Second segment of antennae produced into an earlike 



process (fig. 13 :49&) 2 



— Second antennal segment not thus produced; southeast The larvae and most of the adults of this family are 



U.S Pelonomus Erichson 1847 



2. Antennae approximate; thorax with sharp-edged longi- 

 tudinal line on each side Dryops Olivier 1791 



Dryops arizonensis Schaeffer 1905; Arizona 



— Antennae widely separated, thorax without longitudinal 

 line; northern America Helichus Erichson 1847 



Larvae 



1. Abdominal segments 1-7 with patches of raised hydro- 

 fuge pile above and below each lateral spiracle, 9th 

 abdominal segment with dorsal surface flattened, 

 ventral operculum with 2 clawlike tubercles on posterior 

 margin Helichus Erichson 1847 



- Lateral spiracles without differentiated or raised 

 areas, 9th abdominal segment with dorsal surface 

 strongly convex, operculum without tubercles 2 



2. Body integument with a reticulate pattern of small 

 punctures; gular sutures obliterated, with 2 pairs 

 of setae near where the sutures would be 



Pelonomus Erichson 1847 



- Body integument without reticulate pattern of small 

 punctures; gular sutures present, only 1 pair of setae 

 on gula near suture Dryops Olivier 179 1 



Key to the California Species of Helichus Erichson 

 Adults 



1. Abdominal sternites uniformly densely pubescent. . . 2 



— Pubescence of last sternite not matching that of pre- 

 ceding sternites 3 



2. No dependable external characters; male genitalia 

 (fig. 13:49c) with paramere, as viewed from side, 1/2 

 as wide as long, clasping aedeagus below from apex 

 past the middle; Utah, New Mexico, central and southern 

 California in valley and foothill streams 



immsi Hinton 1937 



— Paramere (fig. 13:49<f) as viewed from side much 

 narrower, 1/2 as wide as long, clasping aedeagus only 

 at the tip; central and southern California in valley 

 and foothill streams productus LeConte 1852 



3. Thorax foveate each side behind middle; male geni- 

 talia as in fig. 13:49e; British Colunbia, Arizona, 

 and California in streams up to 6,000 feet 



foveatus LeConte 1852 



— Thorax without such indentations (fig. 13:49/); Mex- 

 ico, Utah, and California in streams at lower elevations 



suturalis LeConte 1852 



REFERENCES 



HINTON, H. E. 



1937. Helichus immsi, sp. n. and notes on other North 



American species of the genus. Ann. Ent. Soc. Amer., 



30:317-23, 1 text fig., 1 pi. 

 1939. An inquiry into the natural classification of the 



Dryopoidea, based partly on a study of their internal 



anatomy (Col.). Trans. Roy. Ent. Soc. London, 89: 



133-184, 105 text figs., 1 pi. 

 MUSGRAVE, P. N. 



1935. A synopsis of the genus Helichus Erichson in the 



United States and Canada, with description of new 



truly aquatic but are unable to swim. They are found 

 crawling about on the bottom of the stream or cling- 



Fig. 13:50. Elmidoe, larvae, a, Zaitzevia sp.; b, Phanocerus 

 c/avicorn/s; c, Narpus sp.; d, Promoresia sp.; e, Hetcrelmis sp.; 

 i, Dubiraphia sp. (a,c,d, West, 1929; b,e, Hinton, 1940; ^Sander- 

 son, 1954). 



