wheeler: ants of the genus formica. 431 



Head and thorax yellowish red, gaster black; posterior portion of 

 head, front, middle of clypeus, borders of mandibles, posterior border 

 of pronotum, remainder of thorax, except in some specimens, the 

 anterolateral corners of the mesonotum, upper portion of petiole, 

 legs, and antennae, dark brown. Wings slightly infuscated, with 

 brown veins and stigma. 



Male. Length 7-9.5 mm. 



Body opaque. Head and thorax more coarsely shagreened than 

 in the European rufa. Frontal area somewhat shining. 



Hairs and pubescence gray, not black as in the typical rufa and more 

 abundant on all parts of the body. Pubescence longer and denser 

 on the legs and gaster so that this region is not shining. Tibiae with 

 sparse, oblique hairs. Eyes hairy. 



Deep black throughout, including the legs ; genital sclerites yellow- 

 ish at their bases. Wings as in the female. 



Host (Temporary). Unknown, probably one of the boreal forms 

 of F. fusca. 



Type locality. — Colorado. 



Colorado: Florissant, Lake George, Boulder, Malvern, Salida, 

 Denver, Colorado Springs, Buena Vista (Wheeler); Breckenridge, 

 West Cliff (P. J. Schmitt); Fort Collins (C. P. Gillette); Ute Pass, 

 South Park, Leadville (H. C. McCook); Steamboat Springs (T. D. A. 

 Cockerel!) . 



Montana: Nigger Hill, Powell County (W. M. Mann). 



New Mexico: Pecos (T. D. A. Cockerell); Beulah (Mrs. W. P. 

 Cockerell); Barela Mesa (Miss Anna Gohrman). 



Utah: Lehi (W. A. Hooker). 



Texas: Fort Davis (Wheeler). 



Idaho: Lewiston, Market Lake, Collins, and Moscow (J. M. 

 Aldrich). 



Wyoming: Carbon County. 



North Dakota: Jamestown (H. C. McCook). 



Alberta; Medicine Hat (J. C. Bradley). 



Emery cites this form from Nebraska, Colorado, and Dakota but 

 I prefer to regard Colorado as the type locality. The female men- 

 tioned by Emery from Louisiana probably does not belong here. 

 Emery's description is unfortunately very brief and he does not suffi- 

 ciently differentiate this form from obscuripcs. Forel states emphati- 

 cally that obscuripcs has only pubescence on its tibiae. I find that all 

 specimens of aggcrans have prominent oblique hairs on the tibiae, 

 though sometimes few in number. This and the opaque, more pubes- 

 cent, grayish gaster, and much more abundant pilosity on the body in 

 general serve to distinguish the worker of aggerans. 



