244 Annals Entomological Society of America [Vol. VI, 



Of the males 90% had only one pair of ocellar bristles. 

 These were proclinate and had their insertion within the tri- 

 angle. There was a tendency toward the production of 

 two pairs; in some cases this second pair was hardly stronger 

 than the surrounding hairs; in 7% of cases they had devel- 

 oped into a weak posterior pair; and finally in a solitary 

 instance two distinct pairs were developed. 



The width of front affords a secondary sexual character. 

 This character was very constant, there being practically 

 no variation in all the material examined. 



In the females the width was one-seventh to one-eighth head 

 width. Hough in his description of this species gives one- 

 sixth to one-eighth head width; this will hold good if that 

 portion near the ocellar triangle is taken into consideration, 

 as at this extremity there is an expansion. In the present 

 study, however, the term width of front is restricted to that 

 portion of the front immediately above the base of the anten- 

 nae, i. e. the narrowest portion. 



In the case of females the width of front was from one-tenth 

 to four-tenths head width. 



It may be stated here that measurements of all these flies 

 was not attempted. A small series however of each sex were 

 measured in this particular and with these as a guide the other 

 specimens were visually compared. This may sound somewhat 

 casual, but in reality the method is reasonably accurate as the 

 observer very quickly acquires a due sense of proportion. 



The next character lies in the color of the palpi. This 

 character was sometimes very difficult to determine because 

 the palpi were often retracted into the oral cavity. The wall 

 of this cavity varied from an amber yellow color to almost 

 black and the palpi, being semi-transparent, appeared in many 

 cases to be of this dark color and only by removing them could 

 the fallacy be made patent. Again these palpi were covered 

 with fine white hairs and thus in certain planes of vision they 

 appeared white. 



The prevailing color of these palpi was amber yellow. 

 This was however by no means constant, there being but 64.4% 

 of the flies with the palpi of this color. The color varied from 

 pale yellow through dark amber yellow to almost black; again 

 in several cases there was an infuscation or dark area at the 

 distal region; and also a black area was occasionally present 



