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Illinois Natural History Survey Bulletin 



Fol. 23, Art. 1 



uniformly smoky, with long brown hair and 

 dark shading along the cord. Abdomen of 

 male with seventh and eighth tergites heavi- 

 ly sclerotized, and covered with minute 

 and lacelike fenestrations. Male genitalia, 

 fig. 821: tenth tergite consisting of a long 

 stylelike projection twice as long as cerci; 

 cerci ovate, wide and rounded at tip ; clasp- 

 ers with a wide, long basal portion suddenly 

 narrowed to an apical elongation; the apices 

 of the two claspers curve mesad very much 

 as in figure 8225, except that they curve 

 more sharply and usually touch or overlap 

 at the extreme tip; aedeagus large, with a 

 greatly expanded bulbous base which nar- 

 rows to a ventral beaklike spatula above 

 which extrude several membranous folds 

 which enclose three short hooks, a curved 

 sclerotized rod twice as long as these hooks 

 and another curved sclerotized rod stouter 

 and longer than the preceding. Female geni- 

 talia, fig. 825, with ninth sternite mostly 

 membranous but with the bursa copulatrix 

 developed into several pairs of ovate sclero- 

 tized folds and with a basal pair of long 

 sclerotized rods which project into the ab- 

 domen. 



We have only a single record of this 

 species from Illinois, a male collected at 

 Principia College, Elsah, June 28, 1943, 

 at light, C. L. Remington. The range of 

 the species embraces many of the eastern 

 states, including Georgia, Illinois, Kentucky, 

 Maryland, Ohio, Tennessee, Virginia and 

 Wisconsin. In spite of its wide distribution, 

 collections of this species are infrequent, 

 probably indicating a scattered type of dis- 

 tribution pattern. 



Oecetis ochracea (Curtis) 



Leptocerus ochraceus Curtis (1825, pi. 57). 

 Oecetis ochracea carri Milne (1934, p. 16); 

 cf , 9. New synonymy. 



Not yet taken in the state, but of very 

 wide distribution to the north. This is a 

 Holarctic species with records in North 

 America from Alaska, Alberta, Manitoba, 

 Minnesota, Saskatchewan, South Dakota 

 and Wyoming. 



Oecetis species a and b 



We have segregated two distinctive larvae 

 which have not yet been reared. 



Species a. — Fig. 812. Length 6 mm. 

 Head and body sclerites cream colored, 



the head and pronotum with small dark 

 spots or bars, the head with three additional 

 dark areas on and near the frons. Case 

 tubular, slightly horn shaped, constructed 

 of sand grains and usually even in finish. 

 The great similarity between the structural 

 characters of this larva to inconspicua sug- 

 gests strongly that this is the larva of im- 

 mobilis ; immobilis is most closely related 

 on adult structures to inconspicua and occurs 

 in some numbers around Fox and Channel 

 lakes, in which this larva a has been found. 



Illinois Records. — Channel Lake: 

 May 31, 2 larvae. Fox Lake: May 15, 

 1936, from stones, Ross & Mohr, 8 larvae. 

 Mineola, East Fox Lake: June 9, 1938, 

 Mohr & Burks, 4 larvae. 



Species b. — Length 5.5 mm. Head, pro- 

 notum and legs cream colored with dark 

 spots on head and pronotum; mesonotum 

 with a pair of irregular dark areas on each 

 side of the meson. Case horn shaped, con- 

 structed of sand grains and with a very 

 smooth exterior. We have taken only one 

 specimen of this larva, in Channel Lake 

 near Antioch, Illinois, May 18, 1938, Ross 

 & Burks. Aside from immobilis, the only 

 species of adult taken in this region which 

 has not been reared is osteni, and it is possi- 

 ble that this species b is the larva of osteni. 



Triaenodes McLachlan 



Triaenodes McLachlan (1865, p. 110). 

 Genotype, by present designation: Leptocerus 

 bicolor Curtis. 



Triaenodella Mosely (1932, p. 308). Geno- 

 type, by original designation: Triaenodella 

 chelijera Mosely. 



Ylodes Milne (1934, p. 11). Genotype, by 

 original designation: Triaenodes grisea Banks. 



Diagnostic characters for the genus in- 

 clude the long body and case of the larva, 

 its divided hind tibiae and lack of swimming 

 brush on hind legs; the curious mandibles 

 of the pupa, with their large base and slen- 

 der blades; and, in the adult, the venation 

 of the front wing, fig. 733, absence of epi- 

 cranial stem on the head, and katepisternum 

 truncate at apex. Most of the larvae make 

 cases of short, slender twigs built into a 

 spiral pattern, fig. 862. 



The genus has been divided into Ylodes 

 and Triaenodella; it seems best at the pres- 

 ent time to consider these as subgenera. 



The genus contains many North Ameri- 

 can species; a few are widespread, but many 



