270 DIPTERA OF NORTH AMERICA. [PART II. 



the third longitudinal vein ; hind transverse vein moderately ob- 

 lique and nearly straight. 



Female. Face somewhat broader than in the J\ All bristles 

 perceptibly shorter. Abdomen, in the usual position of the seg- 

 ments, without black bands. Pore coxae yellow, at the extreme 

 basis often colored with gray ; their white pubescence much 

 shorter and the black bristles more striking. All the femora 

 altogether yellow, fringed upon the under side with but very short, 

 erect, whitish hairs. Tibia? quite yellow, the hindmost somewhat 

 infuscated only at the extreme tip. The bristles of the tibiae are 

 quite like those of the J\ still some of the bristles are missing, or 

 at least shorter. Tarsi plain, somewhat shorter than in the J 1 ; 

 the first joint of the middle tarsi brownish-yellow, upon the under 

 side with but a few very short black bristles. 



Hab. New York, Illinois. (Osten-Sacken.) 



Observation 1. — With P. scobinator begins a series of very 

 closely resembling species, which agree in a remarkable manner 

 not only in size and coloring, but also in the majority of the 

 plastic characters. The structure of' the middle feet in the £ • 

 shows differences, which leave no doubt as to their specific dis- 

 tinctness. The distinction of their females offers such difficul- 

 ties, that I am unable to overcome them with the materials at my 

 command. I have received P. scobinator in so large numbers, 

 that the j belonging to this species is surely abundantly repre- 

 sented among them ; but whether I have not confounded with it 

 females of the three following species, I am not able to tell. 

 Some of the females, I suspect, belong to P. caudatulus, others 

 may be P. inermis, but I am not positively certain about any one 

 of them. Positive characters for the distinction of the females 

 of these species can only be acquired by the observation of the 

 species in life. 



Observation 2. — There is no doubt that P. femoratus Say 

 belongs to the present group. Whether it is one of the species 

 known to me, and which of them, I cannot decide, as Say does 

 not mention any of those plastic characters by which alone they 

 can be distinguished, and as the J 1 specimen sent by Say to 

 Wiedeman has not been preserved in the collection of the latter. 



