478 PROCEEDINGS OF THE NATIONAL MUSEUM vol. ii5 



Polycentropus cinereiis Hagen 



Figure 5,g 



Polycentropus cinereus Hagen, 1861, p. 293. — Ross, 1944, p. 67 (male and female, 

 larva) . 



Ross (1944) provided good figiu'es of the head and anal prolegs of 

 the larva of this species, but unfortunately did not illustrate the 

 mandibles. During the preparation of this paper I examined the 

 larval mandibles in a male metamorphotype and discovered they had 

 the dorsal margin overhanging the ventral (fig. b,g). The presence 

 of this characteristic in a species of Polycentropus renders the key 

 proposed by Ross (1944) incorrect. For this reason the color of the 

 muscle scars on the head is used in place of the shape of the mandibles. 

 This characteristic is not only constant in all specimens of the genus 

 examined by me, but also in the exotic species for which descriptions 

 are available. 



Genus Psychomyia Pictet 



The larvae of this genus have been relatively well known for a 

 long time, those of the European species bemg fii*st described around 

 the turn of the centmy. Ross described the immature stages of the 

 Nearctic P.flavida in 1944, and the larva of the other eastern species 

 is described here. The larvae of this genus are easily separated 

 from all the other loiown Psychomyiinae by the presence of well- 

 developed ventral teeth on the anal claw. 



Key to Larvae of Psychomyia 



1. Anterior margin of frontoclypeus with a conspicuous pair of submesal proc- 

 esses P. nomada 



Anterior margin of frontoclypeus with submesal processes almost obso- 

 lete P. flavida 



Psychomyia nomada (Ross) 



Figure 5, c-e 



PsTjchomyiella nomada Ross, 1938a, p. 138. 

 Psychomyia nomada. — Ross, 1944, p. 75 (male). 



This species, which has been reported only from the Great Smoky 

 Mountain region of North Carolina, is now recorded from Virginia. 

 During the summer of 1961 I was able to collect a number of meta- 

 morphotypes of this species, thereby correlating the three stages. 



Larva. — Length 6-7 mm. Sclerites pale yellowish brown, nearly 

 immaculate; membranous areas greenish. Frontoclypeus with 

 anterior margin bearing a pair of conspicuous projections submesally 

 (fig. 5,c). Mandibles with several broad mesal teeth (fig. b,d). 



Material. — Virginia: Broad Run, Thoroughfare Gap, Fauquier 

 County, May 22, 1961, P. J. Spangler, 9d^ 19 (USNM); May 27, 



