176 CHARLES ROBERTSON. 



BOMBING. 



Females. 



Hind tibia convex, evenly hairy, the hairs short; vertex yellow. . Psitliyrus. 

 Hind tibia more or less concave, bare, the edges with long hairs forming the cor- 



bicula or pollen-basket 1. 



1. Ocelli small, near supraorbital line, above the narrowest part of the front, tbe 



lateral ones about as far from the eye as from each other... Bombus. 

 Ocelli large, below supraorbital line, in the narrowest part of the front, the 



lateral farther from each other than from the eye Bombias. 



Males. 



Malar space much shorter than wide; ocelli large, frontal, the lateral one less 

 than its diameter from the eye; eyes large ; front narrow; vertex de- 

 pressed ; joint 3 as long as, or longer than, 5; vertex yellow in local 

 species; posting themselves on some high stand and repeatedly flying 

 out and returning Bombias. 



Malar space about as long as wide; ocelli small, vertical, the lateral ones about 

 as far as from the eye as from each other; eyes small; front broad ; 

 joint 3 usually shorter than 5 1. 



1. Outer face of hind tibia bare, or nearly so, the posterior border with long hair. 



Bombus. 



Outer face of hind tibife with hair not much shorter than that of posterior 



border 2. 



2. Vertex black; a black band between the wings Bombus- 



Vertex with yellow; a black patch between the wings; malar space a little 



shorter than wide; " genitalia, squama and lacinia membranous." 



Psitliyrus. 



x BOMBIAS gu. nov. (Type B. auricomus nom. nov.). 

 Females. 



Lateral ocellus about one-half as far from supraorbital line as from the nearest 

 eye; thorax yellow, disc mixed with black ; segment 1 and basal mid- 

 dle of 2 yellow, the latter sometimes inclining to reddish ; malar space 

 shorter than wide separatus. 



Lateral ocellus about as near the eye as to supraorbital line ; thorax in front yel- 

 low 1. 



1. Base of labrum with transverse, narrowly interrupted ridge; joint 3 = 4 + 5, 

 the latter equal ; vertex entirely, or with two lines or two tufts, yel- 

 low ; scutel mixed with yellow and black, sometimes entirely yellow 

 or black; segments 2-3 yellow; 1 black, always so in the middle, the 

 black hairs often extending upon the basal middle of 2, sometimes 

 yellow on the sides ; malar space about as long as wide- .auricomus. 

 Base of labrum with two widely separated tubercles; joint 3 a little shorter 

 than 4 -f- 5, 5 longer than 4 ; malar space about one-half as long as 

 wide ; scutel and segments 1 2 yellow scutellaris. 



