AMERICAN DIPTERA. 227 



In all the specimens which I have seen, a limited number, 

 the submarginal cell has been closed at or a little before the 

 margin of the wing. Mr. Jones (Trans. Am. Ent. Soc. Phila., 

 XXXXIII, 274, 1907) has found a wide variation in connec- 

 tion with the first posterior cell, stating that ten specimens 

 "vary in wing venation from having the first posterior cell 

 slightly narrowed, through one closed in one wing and nearly 

 closed in the other, to both closed." Dr. Williston has noticed 

 this same variation. Mr. Jones finds that there is a great 

 variation also in the color of the legs, stating that in the ten 

 specimens above referred to that the color varied from nearly 

 entire yellowish-red to specimens in which only the extreme 

 base of the femora and apex of the tibias were reddish. The 

 color of the legs of sexfasciata vary in less degree. With such 

 variation in color in species which vary so little from each 

 other structurally, new species should be erected only after 

 study of ample material. 



Osten Sacken, in his Catalogue, doubtfully refers Dasypogon 

 albiceps Macquart (Dipt. Exot., Suppl., I, 69) from Texas to 

 this genus. Of this species Macquart writes, " Head white. 

 Thorax cinereus, with black stripes. Abdomen black, with 

 white fascia. Legs black, knees reddish. Length 4 lines. A 

 neighbor of Laphystia sexfasciata. Face, mystax, beard and 

 front of a silvery white. Antennae black, with light, white 

 down, first segment with white pile; little yellow on the sec- 

 ond. Abdomen; posterior half of each segment white. Legs 

 with light pile and long white silky hair, knees yellow. Wings 

 a little yellowish, veins normal." 



SYNOPSIS OF SPECIES. 



1. Abdomen wholly pruinose except a small spot in the middle of 



the anterior margin of segments 6-7 opaca. 



Abdomen with pruinose bands on the posterior margins of the 

 segments 2 . 



2. Pruinose bands of the abdominal segments entire 3. 



Pruinose bands of the abdominal segments interrupted. 



sexfasiata. 



3 . Abdomen wholly black flavipes. 



Abdomen partly reddish, especially on the posterior margins under 



the bloom liniatiila. 



TRANS. AM. ENT. SOC, XXXV. JUNE, 1909. 



