182 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 1 



Fig. 641. — Platycentroptis radiatus cf. 



and legs brownish yellow with irregular 

 darker markings. Pronotum with a trans- 

 verse depression. Abdominal gills long and 

 single beyond base, arising in groups of one 

 to three. Lateral line conspicuous. 



Case. — Length 23 mm., constructed of 

 fiber and wood fragments to form a round 

 and very thick case of log-cabin construc- 

 tion and usually very fuzzy in appearance. 



Adults. — Fig. 641. Length 20-23 mm. 

 General color a medium shade of brown, the 

 wings with a very distinct pattern of various 

 shades of brown ranging from almost cream 

 color to chocolate, as in fig. 641. Fifth, 

 sixth and seventh sternites in both sexes 

 with a row of projecting sclerotized teeth. 

 Male genitalia, fig. 642: cerci small and 

 cushion shaped, bearing a black mesal area ; 

 tenth tergite forming a pair of long, pointed 

 processes which are black and striate on 

 the dorsal surface; claspers small and incon- 

 spicuous. Aedeagus as in fig. 642. Female 



Fig. 642. — Platycentropus radiatus, genitalia. 

 A, male; B, aedeagus; C, female. 



genitalia, fig. 642, simple, without long or 

 complicated processes. 



Neotype, male. — Northern Illinois, Pea- 

 body Collection. 



The neotype fits Say's description well, 

 and records indicate that the species occurs 

 throughout the bounds of the old "North- 

 west Territory," which included Illinois, 

 Michigan, Minnesota and Wisconsin. 



The occurrence of specimens of this spe- 

 cies in old collections, such as Peabody's, may 

 indicate that radiatus was more abundant in 

 earlier years. This circumstance is undoubt- 

 edly true of some of Say's other species. 



In Illinois this species has been taken at 

 Palos Park (near Chicago) and along the 

 Kankakee River at Momence (see p. 5). 

 At this locality one female was taken at 

 lights ; in addition to this we took moderate 

 numbers of the larvae on drift along the 

 river bank after a very heavy flood. We 

 have taken larvae of this species in abun- 

 dance in some of the small streams in north- 

 western Indiana which are the headwaters 

 of the Kankakee River, but we have taken 

 the larvae at Momence only after a flood 

 stage of water. We think it highly probable 

 that this species does not normally live in 

 the river at Momence but is periodically 

 washed down from small streams. Larvae 

 from Momence were reared. 



The range of the species extends through 

 the East and Northeast ; records are known 

 from Georgia, Illinois, Indiana, Manitoba, 

 Massachusetts, Michigan, Minnesota, New- 

 foundland, New York, Ontario and Wis- 

 consin. 



Illinois Records. — Momence, Kankakee 

 River: June 4, 1932, Frison & Mohr, 1 $ ; 

 May 19, 1937, Ross & Burks, many larvae, 

 1 $ pupa (reared). Palos Park: June 19, 

 1909, W. J. Gerhard, \$, fm ; June 24, 

 1922, W. J. Gerhard, 1 ? , fm. 



