466 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 113 
It was hoped that this larval study would substantiate Ross’ 
theory (1956) of the phylogeny of the genus based on male genitalia. 
Such proof was not found, although species obviously very closely 
related as adults are very similar as larvae. No characters were 
found that tended to substantiate the branches or large groups pro- 
posed by Ross. The situation becomes even more chaotic when one 
considers the larvae from other parts of the world. The lack of 
order may be partially due to convergence of larvae with similar 
habits—perhaps the larvae with edentate mandibles are more pre- 
daceous than those with toothed mandibles; or perhaps the correct 
phylogenetic scheme for the genus has not yet been discovered. 
The length given is that of the longest larva seen. Where not 
given, the length of the prepupa is generally one-fourth to one-third 
less than the length of the mature larva. The term “‘prepupa”’ refers 
to a larva that has spun the pupal cocoon, but has not yet trans- 
formed to the pupa. 
I have made no attempt to give a complete bibliography for each 
species. Rather, the original description is cited, and one or two recent 
redescriptions, if necessary for recognition of the species, plus all 
references adding to the knowledge of the immature stages. 
All the material is in the author’s collection unless otherwise indi- 
cated: Illinois Natural History Survey (INHS), Cornell University 
(CU), and the United States National Museum (USNM). 
I am indebted to Dr. H. H. Ross of the Illinois Natural History 
Survey and to Dr. H. Dietrich of Cornell University for the use of 
material in their collections. 
Because of the tight cocoon that the rhyacophiline larva spins 
around itself before pupating, the metamorphotypic method is very 
effective for associating all stages. Within the cocoon are found the 
larval sclerites, the pupa, and, for a short while before emergence, 
the fully developed genitalia which are visible within the pupal skin. 
A specimen exhibiting all these conditions was named a metamorpho- 
type by Milne (1938). 
Genus Rhyacophila Pictet 
Rhyacophila Pictet, 1834, p. 181.—Ross, 1956, pp. 75-109 (descriptions of most 
species and phylogeny within the genus). 
The larvae of this genus have been accurately characterized by 
Nielsen (1942, pp. 337-358) and Ulmer (1957, pp. 128-131). For this 
reason, I will give only the key larval characters of the genus: Shape 
campodeiform. Pronotum sclerotized, mesonota and metanota mem- 
branous; no prosternal sclerite. Foreleg generally broader than other 
legs but not chelate. Gills present or absent, but neither borne on 
long conical projections nor occurring as areas of 50 or more individual 
