104 MICHIGAN SURVEY, 1905. 



certain, altitude and latitude both tend to make smaller and darker colored 

 specimens of a species. 



5. ANTS FROM THE PORCUPINE MOUNTAINS. 



1. Formica impexa Wheeler.* III. 6. A colony of this form was found 

 beneath a loose stone among the huckleberry bushes on the mountain top, 

 August 12, 1904 (not 1902 as given by Wheeler). 



"Worker. Length 3.3 — 6 mm. 



"With the habitus of Formica rufa. Mandiljles 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 corners 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 lew and rounded. Petiole 

 rather thick anteroposteriorly, its anterior surface convex in profile, its 

 posterior flattened, its edge, especially in smaller workers, very blunt. Seen 

 from behind the node is produced upwards in the middle and is 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 clypeusuneven. 

 Frontal area shining. Remainder of body opac{ue, distinctly but finely 

 shagreened. 



"Whole body and appendages covered with very minute white pubescence, 

 which is rather sparse on the head and thorax, but dense and concealing 

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

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

 gaster they are uniformly distributed and very conspicuous in certain lights. 

 They are also very numerous and prominent on the upper surface of the 

 thorax, clypeus, front, vertex, posterior corners and lower surface of the 

 head. They are 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. All specimens, even the largest 

 are more or less infuscated as follows: Mandibles, anterior border of clypeus 

 and apical half of funiculi dark reddish brovN^i. ' Ocellar triangle, upper 

 surface of pro- and mesonotum, much of the upper portion of the petiole, 

 legs and coxae, except their articulations, more or less blackened. In the 

 largest workers the fore coxae are largely red. Anal region and articula- 

 tions of legs 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, 1904 by Mr. 0. McCreary 

 from a colony nesting under a stone in the Porcupine Mountains, Ontonagon 

 county, Michigan. Types in the American Museum of Natural Histor}-, 

 cotypes No. 32,925 in the University Museum, University of Michigan, 

 Ann Arbor, Mich. 



"F. impexa is allied to F. oreas Wheeler and F. microgijna Wheeler, with 

 which it agrees in having erect hairs on the antennal scapes. It differs 

 from F. oreas in the much stiffer 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 



*Wheeler, W. M. New Species of Formica. Bull. Amer. Mus. Nat. His., XXI, p. 273, 1905. 



