364 



AMERICAN HYMENOPTERA. 



As Stated under the description of niixtus, frigidus is closely- 

 related to that species. It also has a very close ally in the 

 European B. rajellus (Kirby) (= true derhamellus (Kirby) 

 some variations of which it somewhat closely resembles in 

 coloration and general appearance. It can, however, be sepa- 

 rated from that species by structural characters. I have 

 seen both queens and males of rajellus, labelled by both Sch- 

 miedeknecht and Kriechbaumer, and have noted differences 

 between the two species as follows : 



B. friffidiis F. Sm. 



Females. 



Occiput al- 

 ways yellow. 

 Lower part of 

 pleura always 

 covered to 

 bases of legs 

 with light yel- 

 low pile. 



Males. 



Very strong 

 yellow tuft on 

 face. Interalar 

 band distinct 

 and well defin- 

 ed. Fore and 

 hind fringes of 

 posterior tibiae 

 very long. Pos- 

 terior border of 

 hind metatarsi 

 with fringe of 

 long hairs. An- 

 tennae (on the 

 average) fully 

 one-fifth their 

 own length 

 shorter than 

 those of rajel- 

 lus ; segments 

 of fiagellum not 

 at all arcuate. 



B. rajellus Kirby. 



Females. 



More or less 

 darker in gen- 

 eral coloration. 

 Occiput always 

 black. Lower 

 part of pleura 

 always dark. 



Males. 



A few yellow hairs 

 on the face, mixed 

 in with the black. 

 Interalar band not 

 well defined, the dor- 

 sum and pleura be- 

 ing comparatively 

 quite dark. Hind 

 tibiae with front 

 fringes short and 

 hind ones only mod- 

 erately long. Poste- 

 rior border of hind 

 metatarsi without 

 fringe of long hairs. 

 Fiagellum of an- 

 tennae considerably 

 longer, in compari- 

 son with the scape, 

 than that of frigi- 

 dus, its segments 

 more or less strong- 

 ly arcuate (fig. 17). 



Bombus (Bombus) pleuralis Nyl. 



? Bombus praticola W. Kirby, Faun. Bor.-Amer., IV, 1837, p. 274, n. 



381. 

 " pleuralis Nyl., Notis. Saellsk. faun, and fl. Fenn. Forh., I, 



1848 (adnot.), p. 231, n. 9. 

 " " Cresson, Proc. Ent. Soc. Phila., II, 1863, p. 96, n. 



14. 



