421 



gills on segment 2 with one filament; gills on the other segments with 

 2 filaments. Anal appendages of segment 9 short, broad, with a fan of 

 stiff setae. 



Pupal case with open ventral surface; ventral surface covered with 

 grayish tissue; walls made of sand grains or small stones. Pupa lying in 

 a cocoon made of loose tissue with small openings at each end. 



Distribution. Throughout the USSR; cosmopolitan. 



Key to Genera of Polycentropodinae 



Full-grown larva 



1 (9). Pattern of head varying; section "a" of anal legs longer than 

 section "b, " with secondary setae. 



3 (4). Head large, broad, slightly broader than prothorax, with a 



characteristic light small transverse elliptical figure on the 

 frontoclypeus; eyes small or very small. Claws of anal legs long, 

 slightly curved; 2 rows of minute spinules ventrally; a band of 

 spinules near the distal margin on the dorsal side and at the sides 

 1. Plectrocnemia Steph. (p. 475) 



4 (3). Head capsule, markedly longer than broad; smaller eyes. Claws 



of anal legs bent at an almost right angle; 1—3 dorsal spinules 

 larger than the others. 



5 (8). End of claw of anal legs with a small denticle ventrally, or denticle 



absent. 



6 (7). Tibiae and tarsi of forelegs short. Claw of anal legs with a larger 



dorsal spinule; pattern of dorsal surface of head consisting of 

 stripes and dots, distinct 2. Polycentropus Curt. (p. 488) 



7 (6). Tibiae and tarsi of forelegs normal. Claw of anal legs with 2 or 



3 large dorsal spinules; pattern of dorsal surface of head not 

 always distinct 3. Holocentropus McL. (p. 498) 



8 (5). End of claw of anal legs with 4 distinct denticles ventrally 



4. Cyrnus Steph. (p. 51 0) 



9 (l). Posterior part of frontoclypeus with a transverse, slightly undulate 



row of distinct small dark dots. Section "a" of anal legs shorter 



than section "b," without secondary setae 



5. Neureclipsis McL. (p. 519) 



Pupa 



1 (8). Lobes of anal appendages rounded at the end, with setae arranged in 



a fan; subapical spurs of hind tibia of different length. 



2 (7). Labrum with 2 long and 4 short setae. 



3 (4). Fore tarsi without setae; lateral seta of clypeus short; other two 



setae long 1. Plectrocnemia Steph. (p. 475) 



4 (3). Fore tarsi with natatorial setae on segments 2—4; lateral seta of 



clypeus short or long, like the other two. 



5 (6). Setae of first segment of fore tarsi present only apically, sometimes 



absent; lateral seta of clypeus short 



2. Polycentropus Cur-t. (p. 488) 



474 



