August, 1944 



Ross: Caddis Flies of Illinois 



261 



antennae are small, closer to the mandibles 

 than to the eyes, and situated under a carina. 

 The family contains two genera, repre- 

 sented over most of the continent. 



KEY TO GENERA 

 Larvae 



1. Middle and hind tibiae with an inner, 

 apical, seta-bearing spur, fig. 886; 

 hind coxae with a ventral, semicir- 

 cular lobe bearing a row of long 

 setae; mesonotum with sclerites 

 long and narrow, plates of metano- 

 tum heavily sclerotized, fig. 896. . . . 

 Brachycentrus, p. 263 



Hook plates of fifth and sixth segments 

 /ith more and smaller hooks, fig. 



Fig. 886. — Brachycentrus numerosus larva, 

 hind leg. 



Fig. 887. — Micrasema rusticum larva, hind 

 leg. 



Middle and hind tibiae without an 

 apical spur, fig. 887; hind coxae 

 without a ventral lobe; mesonotum 

 with sclerites short and very wide, 

 plates of metanotum only lightly 

 sclerotized but recognized chiefly by 



their cluster of setae, fig. 892 



Micrasema, p. 26 1 



Pupae 



1. Hook plates of fifth and sixth segments 

 with fewer, larger hooks, fig. 888. . . 

 Brachycentrus, p. 263 



VyV Vi 



5A 



u^^m^'^'f^ 





^^^^ 



5P 



I 

 ^ ^"^ 889 



Fig. 888. — Rrachycentrus numerosus pupa, 

 hook plates. 



Fig. 889. — Micrasema rusticum pupa, hook 

 plates. 



889. 



Micrasema, p. 261 



Adults 



1. Front wings with R, suddenly arched 

 and markedly sinuate at base of 



stigmal region, fig. 890 



Brachycentrus, p. 263 



Fig. 890. — Brachycentrus numerosus, front 

 wing. 



F'g. 891. — Micrasema rusticum, front wing. 



Front wings with Ri only faintly sinu- 

 ate at base of stigmal region, fig. 891 

 Micrasema, p. 261 



Micrasema McLachlan 



Micrasema McLachlan (1876, p. 259j. Geno- 

 type, here designated: Oligoplectrum morosum 

 McLachlan. 



This genus is very distinct from Brachy- 

 centrus on the basis of the larvae, but in the 

 adults and pupae it is more difficult to make 

 a separation. All the species of which we 

 have larvae make round cases. Six species 

 are known from North America; of these 

 four are known from the eastern states, but 

 only one has been found in Illinois. 



Micrasema rusticum (Hagen) 



Dasy stoma rusticum Hagen (1868, p. 272); 

 d', 9. 



Micrasema Jalcatum Banks (1914, p. 265); d^. 



Larva. — Fig. 892. Length 6 mm. Head 

 yellow with brown spots, the lower part of 

 the frons entirely brown; thoracic sclerites 

 and legs yellowish. Frons with anterior 

 portion wide. 



Case. — Length 6 mm., constructed of 



