OSTEN SAC KEN ON WESTERN DIPTERA. 333 



the island of Santa Bosa (S. Oal.), through the kindness of Mr. H. Ed- 

 wards. 



Yolucella margmnata Say, Journ. Ac. Phil., vi, 166. — Mexico (Say) ; 

 Waco, Texas (Belfrage) ; a specimen was kindly given by Mr. E. Bur- 

 gess.. 



Yolucella avid a n. sp.— Face with a narrow brown stripe ; cheeks 

 shining, black; abdomen honey-yellow; hind margins of segments and 

 longitudinal narrow dorsal stripe on segments 2-4 black ; wings hyaline ; 

 cross- veins and stigma clouded with dark brown. Length ll-12' nm . 



Antennae, light brown ; arista of the same color, plumose; third 

 autennal joint about two thirds of the length of the arista, its basal 

 half a little expanded ; face pale whitish-yellow, a narrow black stripe 

 runs from the mouth upward, becoming paler and finally obsolete before 

 reaching the antennae; cheeks black, shining; frontal triangle of the 

 male pale whitish-yellow, beset with black pile; profile straight, with a 

 slight depression under the antennae; eyes densely pubescent. Thorax 

 greenish black ; on each side, between the humerus and the scutellum, 

 a rather broad, dull, honey-yellow stripe ; in front of the scutellum, a 

 yellowish, rather obscure parallelogram, emarginate anteriorly; sides 



I of the dorsum and pleurae beset with yellowish white hairs. Scutellum 



• yellowish, subtranslucent, beset with black hair along the edge. Abdomen 

 pale honey-yellow ; first segment black ; the second and third segments 

 posteriorly with a narrow black margin, expanded on each side along 



i the lateral margin, and prolonged in the middle in the shape of a Ion . 



j gitudinal black stripe toward the anterior margin; on segment 2, 

 this stripe is broadly expanded, so as to coalesce with the black of the 

 first segment ; on segment 3, on the contrary, it is tapering anteri- 

 orly; segment 4 with a black cross-band a little beyond the middle, 



; with a subtriangular expansion in the middle, reaching toward the 

 anterior margin ; hypopygium, black ; the abdomen is clothed with short 

 black hairs on its black portions, and with longer yellowish-white pile 

 in the yellow regions, especially on the sides and around the black 

 triangle on the second segment. Femora black ; knees and anterior halt' 

 of the tibiae brownish-yellow; tarsi black. Wings, hyaline; latter half 

 of the subcostal cell and the interval between the auxiliary and first 

 longitudinal vein as far as the stigma brownish ; stigma dark brown . 

 central cross veins and small cross-vein with well denned, although 

 small, brown clouds; the second vein ends in the first, some little dis- 

 tance before the tip of the latter. 

 Hob. — California (G. R. Crotch). A single male. 

 Yolucella satur n. sp. — Face altogether yellow ; cheeks yellow, 

 except a black stripe from the lower corner of the eye to the anterior 

 oral edge ; abdomen honej^-yellow, first segment black, hind, margin of 



J segments 2 and 3 with a narrow black border, that of the second seg- 

 ment connected with the black first segment by a broad black stripe 



