359 

 Leech and Chandler: Coleoptera 



Fig. 13:54. Elmidae, adults, a, Heterelmis longula; b, Microcylloepus sp.; c, Cleplelmis sp.; 

 d, Elsianus sp.; e, Zaitzevia parvulus; f, Phanocerus clavicornis; g, Zaifzevia sp.; adult antenna 

 (a,b,d,f, Hinton, 1940; c, Hinton, 1935; e, Hatch, 1938; g, Hinton, 1939). 



The larvae are distinguished mainly by the number 

 and arrangement of the sternites and pleurae of the 

 thorax and the number of abdominal pleurae. The 

 latter is more variable. Fuselmis has eight, whereas 

 closely related Cleptelmis has seven for one species 

 and six for the other. Microcylloepus which has two 

 meso- and metapleurae in the younger instars was 

 found to have three in the last instars. This may 

 occur in other genera. Body shape and the shape of 

 the ninth abdominal segment are also helpful. The 

 marginal spines are characteristic but have been 

 little used here because a compound spine may appear 

 spatulate at lower magnification. 



Key to Known Genera of Nearctic Elmidae 

 Larvae 



1. Abdominal segments 1-8 with pleura 2 



— ADdominal segments 1-7 or 1-6 with pleura. ELMINI 

 in part 6 



2. Lateral margins of thorax and abdomen expanded, some- 

 times oearing dense rows of erect spatulate spines. 

 LARINI 3 



— Body hemicylindrical or subtri angular, lateral margins 

 not expanded, without conspicuous erect spines. 

 ELMINI in part 4 



3. Sides expanded and body greatly flattened, resembling 

 an elongate suction cup, procoxal cavities closed 

 behind (fig. 13:506) Phanocerus Sharp 1882 



— Sides moderately expanded with coarse compound 

 spines along edge; dorsum with ridge on either side, 

 more pronounced posteriorly, so that last segment is 

 square-sided and flat-topped; procoxal cavities open 

 behind; larger species, up to 16 mm. long 



Lara LeConte 1852 



4. 3ody very elongate, last abdominal segment 6 times 

 longer than wide, operculum only 1/3 as long, tubercles 

 and spines small, inconspicuous; entire body with 

 pubescent appearance (fig. 13:50/) 



Dubiraphia Sanderson 1954 



