470 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 115 



maxillary palpi a long second segment. These characteristics indicate 

 that the species belongs to the genus Cyrnellus, not Cernotina as 

 indicated by Ross (1944, p. 293). The specific synonymy is based 

 on the fact that only one species is known in this genus in the Nearctic 

 region. In addition, several large collections containing both sexes 

 have been made in recent years at Plummers Island, Maryland, the 

 type locality oi fraternus. 



The female metamorphotype which permitted the establishment of 

 the association of larva and adult was borrowed from Dr. H. H. Ross. 

 The larva was included in Ross' key in 1959; however, no description 

 or figures have been published. 



Larva. — Length, 9 mm. Head yellowish, marked with brown 

 which varies greatly in intensity, muscle scars pale (fig. l,a). Labrum 

 slightly more than twice as wide as long (fig. 1,6). Mandibles with 

 dorsal edge overhanging ventral; left mandible lacking mesal brush 

 (fig. 1 ,c) ; right mandible like figure 2,c. Maxillolabium like figure 2,6, 

 except labial lobe barely reaches base of galea. Pronotum sclerotized, 

 generally pale (fig. l,a), sometimes darker, then with pale muscle 

 scars. Legs without any setae greatly shortened, only apical setae of 

 tibiae conspicuously darkened (fig. 1,^). Basal segment of anal 

 proleg bearing setae ventrally and laterally (fig. l,i). Anal claw 

 curved at nearly a right angle, without ventral teeth, but with acces- 

 sory tooth externally at angle (fig. 1,^). 



Material. — Iowa: Keokulc, walls of valve chamber New Lock 19, 

 Aug. 27, 1958, C. R. Fremling, 4 larvae, 19 pupa (INHS). Oklahoma: 

 Texhoma, Dec. 8, 1950, J. E. Silvey, 1 larva (INHS). Tennessee: 

 Cumberland R., near Hermitage Hills, Oct. 11, 1962, S. S. Roback, 

 11 larvae (ANSP); Cumberland R., above Old Hickory Dam, Oct. 3, 

 1959, S. S. Roback, 16 larvae (ANSP); Tennessee R., New Johnson- 

 vUle, Oct. 14, 1958, S. S. Roback, 14 larvae (ANSP); Tennessee R., 

 below Pickwick Dam, Oct. 20, 1959, R. M. Sinclau', 10 larvae (INHS); 

 South Holston R., above Kingsport, Nov. 29, 1945, J. S. Dendy, 3 

 larvae (INHS). Virginia: James R., Richmond, July 26, 1951, J. D. 

 Lattin, 6 larvae (ANSP). 



Remarks. — The larvae of this species are markedly similar to the 

 larvae of Nyctiophylax in having an enlarged dorsal edge of the man- 

 dibles and pale muscle scars; however, the setation of the legs and 

 structure of the anal prolegs and claws indicate an affinity to Poly- 

 centropus. This combination of characters is distinctive. 



I have never collected the immature stages of this species, but Dr. 

 Roback states (in litt.) 'T have found Cyrnellus both in rivers and 

 lake situations on wood and on rock. In the Cumberland River, for 

 example, I found it on rocks up in the lake along the banks and also 



