OP PHILADELPHIA. 53 



tibia dusky; tergum polished, with a large opaque triangle at the 

 base of each segment excepting the first. 



Length two-fifths of an inch. 



The nervures of the wings are arranged in a similar manner 

 with those of X. ater Fab. Meig. [ 31 ] 



PANGONIA Latr. 

 P. iNCisuRALis. [Ante vol. 1, p. 75.] 



TABANUS L. Latr. 



T. MOLESTUS. — Thorax cinereous, lineate with fuscous ; seutel 

 cinereous ; abdomen black-brown, a dilated dorsal vitta. 



Inhabits Missouri. 



A frontal, blackish-brown, glabrous, oblong callus, with a di- 

 lated obscurely rufous glabrous line above, terminating in a 

 smaller dilatation ; antennae black ; proboscis black ; palpi testa- 

 ceous ; thorax [32] cinereous, with four reddish-brown lines; 

 wings dusky, nervures dark-brown, blackish towards the tip, a 

 black carpal line, and a slight anastomosis ; seutel cinereous ; 

 pectus pubescent, cinereous; feet black, tibia obscure ferrugi- 

 nous ; tergum black, a dilated, cinereous, dorsal vitta, consisting 

 of dilated triangular spots on the third, fourth, fifth and sixth 

 segments, the larger ones before ; incisures cinereous. 



Length less than four-fifths of an inch. 



This is one of the species which are called prairie flies ; it is 

 numerous in the prairies of the State of Missouri, and is very 

 troublesome to the cattle. I have seen cattle in the forests 

 which margin the prairies, when attacked by these insects, start 

 suddenly and plunge into the thickets, that the branches may 

 divest them of their enemies. Travellers are much incommoded 

 by them ; many cover their horses with canvas, &c., to shield 

 them from their attacks, or rest in some shaded or secluded situ- 

 ation, during that part of the day when they are most abundant. 



2. T. ANNULATUS. — Thorax cinereous-plumbeous ; wings im- 

 maculate; tergum blackish; incisures cinereous; tibia white. 



Inhabits Missouri. 



Body somewhat pubescent; head beneath cinereous downy; 

 antennae rufous ; palpi white ; proboscis black at tip ; thorax ci- 

 nereo-plumbeous, testaceous in the middle, and clothed with 

 1823.] 



