CADDIS FLY LARVAE—FLINT 489 
Rhyacophila fenestra Ross 
Ficure 10,6 
Rhyacophila fenestra Ross, 1938a, p. 102 (male and female genitalia, larva).— 
Ross, 1944, p. 36 (male and female genitalia, larva).—Ross, 1956, p. 7, 
90 (larva, male genitalia). 
This species still is known to occur only in Illinois; it is common 
in the southern part of the state. 
The following description is based on a series of determined larvae 
from Ross. The larvae of this species and of Jedra correspond in 
Ficure 10.—Rhyacophila species 3: a, head and pronotum, dorsal aspect. R. fenestra: b, 
head and pronotum, dorsal. 
structure with the other members of the group, yet possess a color 
pattern on the head and pronotum strikingly different from the 
rest of the species. 
Description: Length, 16 mm. Head, brownish yellow, becoming 
infuscate mesally and anteriorly, but leaving a large pale central 
spot on frontoclypeus; muscle scars dark and conspicuous laterally 
