100 BULLETIN 31, UNITED STATES NATIONAL MUSEUM. 



the fifth segment a broadly interrupted fascia, in the male more slender 

 than in the female, sometimes yellow with three large oval longitudinal 

 spots. Legs yellow ; hind femora with a rather broad, preajjical, black 

 ring; the hiiid tibine, except the baso and tip, black; hind tarsi more or 

 less reddish, blackish toward the tip. Wings nearly hyaline, stigma 

 subfuscous. 



One male and two female specimens ftom Georgia. The males have 

 the abdomen obscurely brownish reddish beyond the second segment, 

 with narrow indistinct blackish markings. From M. fjeniinata, which 

 it closely resembles, it may be distinguished by the hind femora, which 

 are perfectly straight, and somewhat compressed, not curved and 

 cylindrical; the fifth abdominal segment is, in the femnle, in 31. parvula 

 much longer proportionally than in M. geminata. 



Mesograpta marginata. 



Scaeva marf/inala Say, J. Acad. Phil., ii, 92, 6; Compl. Wr., ii, 80. 

 Syrjihus marginatus Wiedemann, Auss. Zw. Ins., ii, 146,52. 

 Mesogramma planiventri8'Lioew,CeniwY., vi, 49. 

 Siirphm Qninlhin Walker, Dipt. Saunders., 239. 

 Mesograpta marginata Osten Sacken, Cat. Dipt., 125. 



Habitat. — Atlantic. Southern, Middle, and Pacific States ! 



$ . Length, 5 to 6°^™. Face whitish yellow, thinly pollinose, cheeks 

 black. Antennae reddish yellow, a little fuscous above; arista black. 

 Front only moderately narrowed above, greenish black, shining at the 

 vertex, lightly yellowish pollinose below; on the sides below the ocelli 

 narrowly yellow like the face; posterior orbits yellowish pollinose, in 

 some reflections silvery. Dorsum of thorax olivaceous black, but little 

 shining, median cinereous stripe distinct, bordered narrowly on each 

 side with brownish; pleura3 shining greenish black ; beside the yellow 

 spots on the meso and sterno pleur£e, tbere is a third, minute one, above 

 the front coxae. Scutellum yellow, with black pile. Abdomen black, 

 shining, narrowly margined with yellow ; oval, flattened ; first segment 

 at the base, second segment with a median cross-band, third and 

 fourth segments each with a median line and a somewhat oblique large 

 spot on each side attaining the base of the segment, fifth segment with 

 two oblique spots confluent at the tip, yellow. Legs yellow, the hind 

 tarsi a little brownish, blackish at the tip. Wings nearly hyaline. 



This description applies to twenty specimens from Xew York and 

 Connecticnt, which agree quite with Say's description, and hence may 

 be considered as the typical marginata. This species is variable, 

 scarcely any two specimens being precisely alike in the abdominal mark- 

 ings, which makes it seem strange that Loew should base a species upon 

 such characters. The head in the male differs only in the frontal tri- 

 angle being yellow and the vertical triangle black. Of the different 

 variations in the abdomen the following are such as my specimens 

 show : 



Ten specimens from Colorado, all males, are rather smaller than the 

 Eastern specimens and have the scutellum wholly yellow, except a faint 



