558 TERTIARY INSECTS OF NORTH AMERICA. 



the tip of the wing; the fourth longitudinal vein is united by an oblique 

 cross- vein to the third very near the origin of the latter, and the spurious 

 longitudinal vein can not be made out, from poor preservation ; the mar- 

 ginal vein between these two appears to be very simple, the fourth longi- 

 tudinal vein bending downward at its tip to meet it. The abdomen is as 

 broad as the thorax, fully as long as the rest of the body, broad ovate, 

 tapering slightly at the base and rapidly beyond the middle, broadest at 

 the second segment; the first segment is longest and half as long as broad, 

 the second and third slightly shorter, the fourth still shorter, and the fifth 

 minute; the abdomen is light-colored, probably yellow in life, and the first 

 tliree segments are rather narrowly margined posteriorly with black; the 

 first segment is also similarly margined in front, and besides has a median 

 black stripe of similar width, which divides the segments into equal lateral 

 quadrate halves, whence the specific name; the whole abdomen is rather 

 profusely covered with very brief, black, microscopic hairs, which are 

 thickest in the black bands bordering the segments, and next the hind edge 

 of the fourth and fifth segments, producing a dusky posterior margin, sim- 

 ilar to but narrower than the dark belts of the preceding segments, and of 

 course very inconspicuous. 



Length of body, 18 mm ; of head, 85" im ; of thorax, 5.65 mm ; of abdo- 

 men, 9.5 mm ; breadth of front, 2.4 lum ; of head, 4.5 mm ; of thorax, 6""" ; of 

 abdomen, G" 1 '" ; probable length of wing, 145"""; length of hairs on abdo- 

 men, 0.04 ram ; width of dark abdominal bands, 0.5 mm . 



Dr. Williston thinks it can not be a Milesia, but that its affinities are 

 rather with Syrphus. 



Green River, Wyoming. One specimen, No. 14691 (Dr. F. V. Hayden). 



ERISTALIS Latreille. 



ERISTALIS LAPIDEUS. 



PI. 5, Figs. 48, 49. 







Erietalis tepidem Scmld., Bull. U. S. Geol. Geogr. Surv. Terr., Ill, 756 (1^77); Willist., Syn. N. A. 



Syrpb., "Ml, 2->3 (1886). 



A poorly preserved specimen, showing little that is characteristic, but 

 \vhicli belongs near Kristalis or Helophilus. The body is preserved on a 

 dorsal aspect, with wings partially expanded ; the head is nearly wanting, 

 the thorax without markings. The wings are distinct only on the basal 



