MOUNTAIN ANTS OF NORTH AMERICA. 511 



Described from twenty workers taken by Dr. S. J. Hunter in Creede 

 County, Colorado, at an altitude of 8844 ft. 



44. LeptotJiorax (Mychothorax) muscorum Nyl. var. sordidus 

 Wheeler. 



Colorado: Boulder (P. J. Schmitt). 



45. Leptothorax (Mychothorax) muscorum var. septentrionalis var. 

 nov. 



Ifor/iTr. Length 2.5 mm. 



Resembling the var. sordidus, but with the head and gaster dark 

 brown or black above, the paler portions of the body of a deeper and 

 more ferruginous red and the rugosity and punctuation decidedly 

 coarser, so that the head, thorax, petiole and postpetiole are nearly 

 opaque. The petiolar node is blunter and more rounded above in 

 profile than in sordidus and the typical viuscorum of Europe. 



Female. Length 2.9 mm. 



Dark brown; head black; venter yellowish, much of the pleurae 

 lower surfaces of petiole and postpetiole, mandibles, legs and antennae, 

 except the clubs, paler brown. Thorax subopaque, densely punctate, 

 pronotum transversely, mesonotum longitudinally rugulose. Wings 

 white, with colorless veins and brown stigma. Pilosity much as in 

 the worker. 



Male. Length 2.6-3 mm. 



Black, legs and incisures of gaster dark brown. AVings as in the 

 female. Head, thorax, petiole and postpetiole subopaque, densely 

 rugulose-punctate. Pilosity abundant, short and white. 



Described from numerous specimens of all three phases, which I 

 took from several colonies nesting under stones on the southern slope 

 of Tunnel Mt. at Banff, Alberta, a series of workers collected by Dr. 

 C. Gordon Hewitt at Sulphur Springs, near Banff and a few workers 

 which I found in the Yoho Pass, near Emerald Lake, British Columbia. 

 At first sight this ant closely resembles L. rugatulus var. mcdiorufus 

 but it can be readily distinguished by the feeble transverse mesoepino- 

 tal impression and faintly indicated promesonotal suture. 



46. Leptothorax (Mychothorax) acervorum Mayr subsp, canadensis 

 Provancher. 



Washington: Olympia (T. Kincaid). 



Colorado: Florissant (Wheeler); Ward and Pikes Peak, 10,000 ft. 

 (T. D. A. Cockerell). 



