392 C. R. OSTEN SACKEN'S PRODROME 



segment shows four longitudinal spots on yellow ground ; sometimes these spots expand at 

 both ends in such a manner as to leave only a longitudinal yellow stripe in the middle, and 

 a round yellow spot, on black ground, each side ; the fourth segment is colored like the 

 third, so that in some cases the abdomen shows two longitudinal black stripes, reaching 

 from the scutellum to the posterior margin of the fourth segment, and two lateral stripes 

 on the third and fourth segments; in other cases (and, upon the whole, more frequently), 

 the third and fourth segments may be described as black, with a yellow median stripe and, 

 on each side, yellow spots, a pair on each segment. The last segments are black, with yel- 

 low hind margins, the fifth sometimes with a yellow median line. Venter yellow ; third 

 and fourth segments with black spots in the middle (which are nearly obsolete in some 

 specimens), and blackish lines on the sides ; the fifth and following segments black, 

 with yellow margins. Legs as in C. montanus and also variable as to the extent of the 

 black color. Wings : both basal cells hyaline, the brown color encroaching but very little 

 upon either of them ; crossband not quite filling out the fourth posterior cell, and leaving a 

 hj-aline space at its distal end and along the intercalary vein ; a brown shade on the last 

 section of the fifth vein is hardly perceptible ; the hyaline triangle between the crossband 

 and the apical spot entirely separates both and reaches the costa with its apex. 



Hah. Pennsylvania; Massachusetts; White Mountains, N.. II. (Scudder) ; Canada 

 (Couper); Kansas (Al. Agassiz). Twelve female specimens. 



22. Chrysops fallax n. sp. 



?. Apical spot sepnrated from the crossband liy the tip of the hyaline triangle, which almost reaches the 

 co.^ta ; both basal cells li valine ; the crossband reaches the posterior inarr/in. Facial callos-ities reildish or 

 brownish, third and fourth abdominal segments with four black longitudinal spots, alternating with yellow 

 spaces, the black sometimes coalescing in such a way as to leave but a yellow longitudinal stripe in the middle. 



Length, 7-7.5 mm. 



Female. Very like C. 7u7«ris, bttt with the following, apparently constant, differences: 

 it is smaller ; the end of the crossband fills out the fourth posterior cell, or very nearly so ; 

 although the hyaline triangle between crossband and apical spot crosses the second longi- 

 tudinal vein, forming a large hyaline spot in the marginal cell, still a connection is left be- 

 tween the crossband and the apical spot, in the shape of a narrow brown shadow ; the cloud 

 on the last section of the fifth vein is somewhat more distinct ; on the abdomen, the black 

 spots under the scutellum, separated hy a yelloio space in C. hilaris, are here coalescent 

 (this seems to be a very constant character); the converging black lines on the second seg- 

 ment are sometimes coalescent anteriorly; the facial callosities are usually red, often brown- 

 ish on their lower half; the cheeks are also variable, from reddish to black. The abdomen 

 is like that of C hilaris, and shows the same vaiiations as in that species; in some speci- 

 mens the third and fourth segments, except a yellow stripe in the middle, and a yellow hind 

 margin, are entirely black. 



Mcde. Similar to the female ; the proximal ends of the basal cells somewhat infuscated ; 

 thorax Avith erect, j-ellowish hairs; third and fourth abdominal segments (in the two speci- 

 mens before me), yellow, with four black spots; the following segments black, with yellow 

 hind margins. 



