140 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 1 



Apex of abdomen simple and tubular, 

 without platelike or produced ap- 

 pendages, fig. 501 (females) 3 



Figs. 499-500. — Orthotrichia, male genitalia. 

 A, ventral aspect; B, dorsal aspect; C, aedeagus. 



CRIST ATA 



Figs. 501-502. — Orthotrichia, female gen- 

 italia. 



2. Claspers wide, with a sharp, projecting, 



apico-lateral corner; plate back of 

 claspers small and truncate, fig. 500 



cristata, p. 141 



Claspers narrow, converging, together 

 forming a trapezoidal, dark block; 

 plate back of claspers with a pair of 

 long hornlike arms, each tipped with 



a long seta, fig. 499 



americana, p. 140 



3. Eighth sternite with median process 



not flared out at a wide angle toward 

 base; this mesal portion of sclerite 

 distinctly but not heavily sclero- 



tized, fig. 502 cristata, p. 141 



Eighth sternite with median process 

 flared out at a wide angle toward 

 base; this mesal portion membra- 

 nous, fig. 501 americana, p. 140 



Orthotrichia americana Banks 



Orthotrichia americana Banks (1904^, p. 116); 

 cf , 9. 



Oxyethira dors alts Banks (1904^, p. 216); 9. 

 New synonymy. 



Orthotrichia brachiata Morton (1905, p. 70); 



Larva (mature type). — Length 4 mm. 

 Head and thorax brown and robust. Front 

 legs stocky, middle and hind legs very long, 

 with tarsi elongate. Abdomen elliptical, 

 widest near middle but not distended and 

 with the segments not separated by con- 

 strictions. 



Case. — Modification of the purse type; 

 composed of two equilateral halves, the case 

 almost round in cross section, long and with 

 the slits at each end visible from the ventral 

 view only. 



Adults. — Length 2.5-3.5 mm. Color mot- 

 tled with a salt-and-pepper combination over 

 the entire body, and with a pale stripe down 

 meson when wings are folded. Seventh 

 sternite of male with a mesal process cov- 

 ered with a brush of long scales. Male 

 genitalia, fig. 499: ninth segment mostly 

 membranous; tenth tergite forming a pair of 

 long, wide membranous lobes ; claspers 

 small, fused to form a bifid plate ; above 

 these arise a pair of long horns, each bear- 

 ing a long seta at tip; aedeagus very long, 

 with a sclerotized, eversible penis; lying near 

 and above aedeagus is a curved, sclerotized 

 blade. Female genitalia, fig. 501 : eighth 

 sternite with a wide, membranous ventral 

 area; bursa copulatrix nearly circular. 



This species was recorded by Morton 

 (types of brachiata) from Lake Forest, lUi- 



