1905.] Wheeler, New Species of Formica. 273 



5. Formica impexa sp. nov. 



Worker. — Length, 3.3-6 mm. 



With the habitus of F. rufa. Mandibles 8-toothed. Clypeus broadly 

 rounded in front, not produced in the middle, carinate its entire length. Head, 

 excluding the mandibles, distinctly longer than broad, even in the largest 

 workers. Cheeks rather long, straight, subparallel. Posterior border of head 

 straight, posterior comers rounded. Joints 1-4 of antennal funiculus decidedly 

 longer and more slender than the remaining joints. Thorax of the rufa type 

 but with the epinotum very low and rounded. Petiole rather thick antero- 

 posteriorly, its anterior surface convex in profile, its posterior flattened, its edge, 

 especially in smaller workers, very blunt ; seen from behind it is produced up- 

 wards in the middle and of rather variable outline, being notched in the middle 

 in some specimens, but oftener more or less rounded. 



Mandibles lustrous, finely and sharply striated. Surface of clypeus uneven. 

 Frontal area shining. Remainder of body opaque, distinctly but finely sha- 

 greened. 



Whole body and all the appendages clothed with very minute white pubes- 

 cence which is rather sparse on the head and thorax, but dense and conceal- 

 ing the ground surface on the gaster. Body, antennal scapes, and legs covered 

 with coarse, obtuse, erect or suberect, whitish or yellowish hairs. On the gaster 

 these are tiniformly distributed and in certain lights very conspicuous. They 

 are also very numerous and prominent on the upper surface of the thorax, 

 clypeus, front, vertex, posterior comers, and lower surface of head, but absent 

 or very sparse on the cheeks, pleurae, and coxae. On the legs they are prominent 

 both on the flexor and extensor surfaces. 



Head and thorax red. Gaster black. Even in the largest specimens, the 

 mandibles, anterior border of clypeus, and apical half of funiculi are dark red- 

 dish brown; ocellar triangle, upper surface of pro- and mesonotum, much of 

 the upper surface of the petiole, legs and coxae, except their articulations, more 

 or less blackened. Fore coxas largely red. Anal region yellowish. In the 

 smallest workers the infuscation is more extensive, involving the whole of the 

 posterior portion of the head and the epinotum. 



Described from twelve workers taken August 12, 1902, by Mr. 0. 

 McCreary from a colony nesting under a stone on the Porcupine 

 Mountains in northern Michigan. Types in the American Museum of 

 Natural History, cotypes in the University Museum, Ann Arbor, 

 Michigan. 



F. impexa is allied to F. oreas Wheeler and F. microgyna Wheeler, 

 with both of which it agrees in having erect hairs on the antennal 

 scapes. It differs from oreas in the much coarser and less abundant, 

 erect and obtuse hairs on the head and thorax, the prominent hairs on 

 the gaster, the longer head, more opaque surface of the head and 

 thorax, etc. In most of these characters it also differs from the 

 typical microgyna. The erect hairs on the gaster of impexa are much 

 more robust and obtuse than in the latter species. The new species 



Septembery /goj.'\ 18 



