PROCEEDINGS 



OF THE 



CALIFORNIA ACADEMY OF SCIENCES 



Fourth Series 



Vol. IX, No. 8, pp. 257-270 August 26, 1919 



VIII 



KEY TO THE NORTH AMERICAN SPECIES OF THE 



DIPTEROUS GENUS MEDBTERUS, WITH 



DESCRIPTIONS OF NEW SPECIES 



BY 

 MILLARD C. VAN DUZEE 



In the preparation of the following key I have found it 

 necessary to employ a few characters that sometimes are not 

 readily distinguished, but for the species included it should 

 work very well, although, perhaps rather difficult to use on 

 account of these obscure characters. The bristles above the 

 fore coxae are often small and it may be difficult to determine 

 their color. The small tooth at the base of the metatarsi of 

 some of the males is easily overlooked but in those species that 

 have this tooth the metatarsi are narrowed at base for a short 

 distance and the tooth is inserted on the narrowed portion. 

 The scutellum has either one or two pairs of bristles on its 

 margin, but where there is but one pair there is often a pair of 

 small hairs taking the place of the second pair of bristles, and 

 where there are two pairs of bristles the outer pair are often 

 reduced to about half the size of the central pair ; this, how- 

 ever, should give the student little trouble in running the ,.-; ^.^^j 



August 26, 1919 



V. 



