ish: tarsi^ except at base, fuscous: poisers pale 

 yellow: tergum on the basal segment nearly 

 covered with silvery hair; remaining segments 

 each with a silvery band behind, occupying 

 nearly one half of its length, and interrupted in 

 the middle : venter immaculate. 



OBSERVATIONS. 



The specimen is a male. The species is an 

 inhabitant of Pennsylvania, and probably also of 

 several of the neighbouring states. It is very 

 closely allied to the thoracica of Fabricius, with 

 which it has probably been hitherto confounded ; 

 but it differs from that beautiful species by its 

 pellucid wings, pale tibia, broader bands of the 

 tergum, colour of the thoracic hair, and by hav- 

 ing silvery hair on the hypostoma and front. It 

 belongs to the second division of the genus, in 

 which the palpi are cylindrical, or slightly cla- 

 vate and recurved. 



The upper left figure of the plate, 



PLATE XIII. 



