16 BULLETIN 31, UNITED STATES NATIONAL MUSEUM. 



middle femora, aud the hind femora except the tip, black. Wings 

 cinereous, along the costa fuscous. 



C. ventricosum differs from C. arcuati, to which it is nearly allied, in 

 the base of the abdomeu being black pilose. — Translation. 



I have seen a specimen from Canada which I believe belongs here. 



Chrysotoxmn derivatum. (Plate I, figs. 5, oa, 56, 5c.) 

 ChrnsotoxuiH derivatum Walker, List, etc., iii, 542. 

 Chrifsotoxum I'illosulum Bigot, Ann. Soc. Eut. de Fr., 18b3, 323. 



Habitat. — Hudson's Bay Territory, Alaska, Colorado Mountains (O. 

 S.), California, Oregon ! 



9 ,S . Length, 10 to 14™™. Second joint of the antenuai a half or a 

 third as long as the third ; eyes pilose. Pile of thorax black and yel- 

 low. Bands of the abdomen rather slender ; first band separated by 

 a considerable distance from the border, which is not yellow ; the band 

 is usually connected with the posterior angles of the segment by a 

 small yellow spot; third segment with the arcuated cross-band of 

 nearly equal width throughout, narrowly interrupted in the middle, 

 touching, or narrowly separated at the posterior angles from the yellow 

 hind margin; the hind cross-band usually reaches quite to the lateral 

 margin, usually slender, more or less dilated in the middle; fourth seg- 

 ment similar, but the arcuate band broadly connected at the outer 

 angles with the broad hind margin; the posterior band is considerably 

 widened at the middle, so that between the two bands there is in- 

 closed an arched, elongated black stripe ; fifth segment with the yel- 

 low inclosing an inverted V-shaped spot. 



In some specimens, both male and female, the pile on the sides of the 

 base of the abdomen is in large part black ; the arcuate band of the fourth 

 segment is entirely separated from the yellow of the hind margin. Nine 

 specimens. 



Chrysotoxum integre, u. sp. 

 Habitat. — Arizona ! 



9 . Length, 10™'°. Third joint of the antennsB longer than the first 

 two together. First arcuate band of abdomen narrowly interrupted, 

 connected with the yellow of the posterior angles, hind margin of the 

 segment narrowly yellow in the middle ; arcuate band of the third seg- 

 ment entire, connected with the yellow of the hind margin ; anterior 

 angles yellow, posterior marginal band angularly dilated in the mid- 

 dle ; fourth segment similar, the arcuate band more convex, the pos- 

 terior band more dilated, nearly cutting the black in two ; arcuate band 

 of the fifth segment entire, shaped like an inverted U , the yellow of the 

 posterior margin dilated, forming an elongate narrow stripe, between 

 which and the arcuate band the slender black forms an elongate in- 

 verted U. Legs yellow. Wings narrowly brown along the front mar- 

 gin. 



