August, 1944 



Ross: Caddis Flies of Illinois 



263 



Burks, S S, $9,7 pupae, many larvae; 

 Kankakee River, May 24, 1937, H. H. Ross, 

 $ S , 9 9; May 5, 1938, Ross & Burks, 

 S $, 9 9, many pupae; Aug. 19, 1939, 

 Ross & Burks, 1 larva; May 1, 1941, T. H. 

 Frison, 5 $ , 19. 



Brachycentrus Curtis 



Brachycentrus Curtis (1834, p. 216). Geno- 

 type, monobasic: Brachycentrus subnubilus 

 Curtis. 



Sphinctogaster Provancher (1877, p. 262). 

 Genotype, monobasic: Sphinctogaster lutescens 

 Provancher. 



Oligoplectnim McLachlan (1868, p. 297). 

 Genotype, by subsequent limitation of Mc- 

 Lachlan (1876, p. 258): Phryganea maculata 

 Fourcroy. 



Subg. Amiocentrus Ross (1938a, p. 177). 

 Genotype, by original designation: Brachy- 

 centrus aspiliis Ross. 



The larvae of this genus frequently con- 

 struct the well-known chimney case, fig. 

 904, although the case may be cylindrical. 

 Most of the diagnostic characters for the 

 genus are given in the key. 



Nine species are known from North 

 America, two of which have been taken in 

 the state, and another has been taken nearby 

 in Wisconsin. To date characters have not 

 been found for the separation of all females. 

 Many of the larvae present characters use- 

 ful in their diagnosis. 



Of especial interest in this genus are two 

 Say species, lateralis and numerosus. Both 

 of these were described from along the Ohio 

 River at Shippingsport, Kentucky (near 

 Louisville), and recorded as occurring in 

 vast numbers early in May, the wave of one 

 species appearing after the wave of the 

 other. We believe that in the Kankakee 

 River at Momence, Illinois, we have found 

 a duplication of this condition; in fact, so 

 closely do our observations correspond on 

 what are apparently these same two species 

 (belonging to the genus Brachycentrus) that 

 I am selecting neotypes from this Momence 

 material. 



KEY TO SPECIES 

 Larvae 



1. Head entirely black 



light or bright yellow and having 



narrow dark lines, fig. 897 



lateralis, p. 265 



americanus, p. 266 



Head with light marks, figs. 896, 897 2 

 2. Head with pattern predominantly 



897 



Fig. 896. — Brachycentrus numerosus larva. 

 Fig. 897, — Brachycentrus lateralis larva. 



Head with lower portion dark brown 

 and having a pair of cream marks, 

 fig. 896 numerosus, p. 264 



Adults 



1. Genitalia with claspers, figs. 898-900 



(males) 2 



Genitalia without claspers, fig. 901 

 (females) 4 



2. Cerci fused on meson for at least basal 



half; apex of clasper with a lower, 

 rounded platelike lobe, fig. 898. . . 



americanus, p. 266 



Cerci not fused on meson; apex of 

 clasper without a platelike lobe, 

 figs. 899,900 3 



3. Tenth tergite divided at apex, each 



lobe with a long macrochaeta at tip, 



fig. 899 numerosus, p. 264 



Tenth tergite without a pair of ma- 

 crochaetae, in outline shaped as in 

 fig. 900 lateralis, p. 265 



4. Lateral aspect of apical tergite robust 



and long, a crease setting off the 

 apical third as a distinct area round 



at tip, fig. 903 lateralis, p. 265 



Lateral aspect of apical tergite short 

 and truncate or with apical portion 

 as long as base, figs. 901, 902 5 



5. Lateral aspect of apical tergite short, 



apical portion truncate and deeper 



