ADAMS : NORTH AMERICAN DIPTERA. 443 



the general color is similar to that of the thorax, being darker 

 only on the black markings. The male head agrees with that 

 of the female. The mesonotum, except on sides which are 

 whitish pollinose, is darker and with longer pile. The pleurae 

 are generally largely yellowish pollinose, but often with only a 

 longitudinal stripe above base of coxse. The coloration of the 

 abdomen is not so variable as in the female, being yellow, with 

 a prominent median double row of black spots, which are often 

 broadly coalesced on the first, second and third segments, but 

 do not reach the posterior margin. On the third, fourth, fifth 

 and sixth segments are two lateral rows of black spots not at- 

 taining the posterior margin. Often all the spots on the last 

 segment coalesce and the segment is black, except the very nar- 

 row lateral and posterior borders, and often the pollen is dis- 

 lodged leaving the segment shining black. The wing agrees 

 with the female wing, except the two basal cells are infuscated 

 on their basal two-thirds. Halteres in each sex yellow. 



Psilocephala occipitalis, n. sp. 



Male : Occiput black, yellowish in the middle beneath, white 

 pollinose, bristles small and yellowish, vertex yellowish polli- 

 nose, front white pollinose, except upper angles, which are 

 yellowish, face white pollinose, antennae yellow, first joint 

 about twice the length of the second, third slightly longer than 

 the first, its extreme tip and arista black, mouth-parts yellow, 

 sparsely yellow pilose, cheeks yellow pollinose. Thorax yellow, 

 mesnotum and dorsum of scutellum with a coating of yellow 

 pollen, the very small yellow pile few in number, bristles yel- 

 low, four in number on the scutellum, pleurae, under side of 

 scutellum, and metanotum with a coating of white pollen, hal- 

 teres 3'-ellow. Abdomen yellow, under side of first segment, 

 apices of second and third white pollinose, sparse yellow pile 

 scarcely perceptible, venter with first segment, apices of second, 

 third and fourth narrowly white pollinose ; legs and their pile 

 yellow, bristles brownish yellow, coxjie white pollinose. Wings 

 hyaline, with a faint fuscous tinge, fourth posterior cell open. 

 Length, 7.9 mm. 



One specimen ; Bill Williams Fork, Arizona. Collected by 

 Dr. F. H. Snow. 



