1 82 DUEHAM DIPTERA. 



XXVIII. 279. 



23 (20). Hind femora partly blackish. 



24 (25). Middle pair of abdominal spots not much longer 



than broad. 



1 49 1. Platychirus clypeatus, Mg. 

 Common in meadows and marshes among rushes. 



25 (24). Middle pair of abdominal spots twice as long as 



broad. Narrow species. 



1492. Platychirus angustatus, Ztt. 

 Bishop Auckland, 1 $, 4-7-01 ; Hesleden, common 

 at rushes. 



26 (1) (8). Fore tibiae and tarsi scarcely at all dilated. 



Smallest species, size 5^ mm. Fore femora with 

 two peculiar long black hairs, one at the middle 

 and one near the tip of the upper hind side. 



(1493. sticticus, Mg.) 



Females (Platychirus, etc.). 



The females are very difficult to distinguish. The follow- 

 ing is from Mr. Verrall's table of the British species of 

 Platychirus, Melanostoma, Melangyna, and Pyrophaena, to 

 which he adds the following note : " This table is bound to 

 be an imperfect one at present, as it is impossible to cope 

 with the various melanoid females which occur in many 

 species." 



(Figures after a Platychirus refer back to the table of 

 males, after other genera forward). 



1 (4). Abdomen all black without any pale or even bluish 



markings. 



2 (8). Size about 9 mm. 



(1500. Melangyna 4-maculata, Verr.) 



3 (2). Size 7 mm. ( r 497- Melanostoma dufo'um, Ztt.) 



4 (1). Abdomen with pale or bluish spots or markings. 



5 (8). Abdomen nearly all indeterminately orange, or with 



only one pair of yellow spots, which are placed on 

 the third segment. Pyrophaena, Schin. (280) 



