OF rHILADELPHIA. 57 



the basal one very short and also obsolete; feet reddish-brown, 

 tibia pale. 



Length a quarter of an inch nearly. 



Nervurcs of the wings as in albiconu's. 



THEREVA Meig. 



1. T. terois[sa]. — Wings spotted ; tergum silvery pruinose. 

 Inhabits East Florida. 



Body blackish ; head blackish-brown, with white hair beneath; 

 antenna), basal joint cinereous with black hair ; palpi pale; pro- 

 boscis dusky; thorax [40] blackish-brown ; wings slightly tinged 

 with brownish, and with several brown spots, and brown stigma; 

 feet pale, dusky at the joints ; tergum dull testaceous, darker at 

 base, and with a bright silvery reflection in a certain position, 

 posterior margins of the segments white. 



Length more than seven-twentieths of an inch. 



The reflected color of the tergum is very similar to that of 

 Musca am'lis ]jinn. It seems to be closely allied to T. pktipnmis 

 Wied., but is larger, destitute of bands on the wings, and the 

 color of the antennse, feet, &c. is difierent. 



[Changed to T. corrnsca by Wiedemann. — Sacken.] 



2. T. NIGRA. — Black ; incisures of the tergum and lateral spot 

 on the fifth segment gray. 



Inhabits Pennsylvania. 



Head glabrous, polished; hypostoma and all beneath, with gray 

 minute hair; antenna) with minute gray hair, and longer sparse 

 black hair on the basal joint; occiput velvet black; wings pel- 

 lucid, stigmata and nervurcs brown, costal edge beyond the stig- 

 mata pale, each of the two ultimate pairs of nervurcs uniting 

 before they attain the edge of the wing ; poisers brown ; scapus 

 pale; pleura, pectus and coxae somewhat glaucous; feet blackish, 

 tibia and tarsi excepting at tip pale, anterior tibia at tip and tarsi 

 blackish ; tergum polished, posterior edges of the third or fourth 

 basal segments gray, spot each side of the fifth segment oblong- 

 oval nbli({ue. 



Length three-tenths of an inch. [41 ] 



1823.] 



