476 PROCEEDINGS OF THE NATIONAL MUSEUM vol. lis 



Grayling, June 17, 1935, T. H. Frison, 1 larva (INHS). Illinois: 

 Rock Cr., Erie, June 5, 1940, Mohr and Bm-ks, 1 larva (INHS). 

 Delaware: West Cr., near Newark, June 7, 1951, T, Dolan IV, 

 2 larvae (ANSP). Virginia: Thornton R., above Sperryville, Apr. 

 15, 1961, O. S. Flint, 1 larva (USNM). 



Remarks. — The larvae of this form have a more elongate head 

 capsule than either of the other species, and the brown spot on the 

 head completely encloses the frontoclypeus posteriorly. The T- 

 shaped patch of spicules on the ninth sternum is present, but much less 

 conspicuous than in the other species. 



To judge by the remarks on the biology of Cyrnus pallidus by 

 Noyes (1914), the larvae must have similar habits to the other species 

 of the genus. 



Genus C, new form 



Figure 4 



These larvae are almost unquestionably Cernotina, and quite pos- 

 sibly C. astern Ross the type locality of which is the same spring from 

 which some of these larvae were collected. 



Larva. — Length 8 mm. Sclerites pale yellowish; head with a dark 

 area centrally on the frontoclypeus which bears pale muscle scars 

 (fig. 4, a). Head capsule conspicuously longer than broad. Labrum 

 about twice as wide as long (fig. 4,6). Mandibles and maxillolabium 

 as in Nyctiophylax. Pronotum sclerotized, mesonotum and metano- 

 tum membranous. Foretibiae and midtibiae with 1 short, dark seta 

 in posterior series and 4 in anterior series; midtibia with an additional 

 apicoventral black seta (fig. 4,c-fif). Basal segment of anal proleg 

 vrith a small number of setae apicomesally (fig. 4,h). Anal claw with 

 4 very long teeth ventrall}^ (fig. 4,%). 



Material. — Texas: San Felipe Spring, Del Rio, Sept. 21, 1960, 

 Flint and CoUette, 8 larvae (OSF); stream, near Bandera, Oct. 9, 1960, 

 Flint and Collette, 9 larvae (OSF). 



Remarks. — The larvae are most closel}^ related to those of Nyctio- 

 phylax, from which they differ in the much longer head capsule, the 

 setation of the legs (especialh^ the fewer dark setae on the posterior 

 row of the tibiae), and in the unique structure of the anal claw. 



They seem to construct the sam.e type of larval shelter as Nyctio- 

 phylax, and frequent similar areas in the same type of streams. 



