432 BULLETIN: MUSEUM OF COMPAKATIVE ZOOLOGY. 



F. aggcrans is undoubtedly the common "thatching ant" of the 

 Western States. It constructs a nest very much hke that of F. tufa 

 pratcnsis in Europe, at altitudes varying from 6,000-8,000 ft. The 

 vegetable debris used in the construction of the mounds is often very 

 coarse. McCook mentions this ant or possibly the true ohscuripes 

 as occurring at Iowa Gulch near Leadville, Colo., at an elevation of 

 11,300 ft. 



28. F. EUFA AGGERANS var. MELANOTicA Emery. 



F. rufa obscurirentris var. melanotica Emery, Zool. jahrb. Syst., 1893, 7, p. 

 644, 650, y ; Wheeler, Ants, 1910, p. 570. 



Worker. Length 4-8 mm. 



Differing from the worker of the typical aggerans in color and pubes- 

 cence. The thorax of even the large workers has a strong tendency 

 to infuscation, so that in some colonies such individuals are black with 

 a red head, which is sometimes clouded with brown in the ocellar, 

 occipital, and frontal region. The pilosity is the same as in the typical 

 aggcrans, but the pubescence on the gaster is more dilute, so that this 

 region is more shining and the shagreened surface is visible. 



Female. Length 8 mm. 



Resembling the female of aggerans, but the infuscation of the thorax 

 is more extensive, involving also the pronotum. Gaster very smooth 

 and shining. 



Male. Length 8 mm. 



Differing from the male of aggerans only in having the gaster more 

 shining, owing to the sparse pubescence. Frontal area scarcely shin- 

 ing. Eyes hairy. 



Type locality. — Wisconsin. 



Wisconsin: Dodges' Corner, Waukesha Co., Waupaca (C. E. 

 Brown); Prairie du Chien (H. Muckermann). 



Illinois: Rockford (Wheeler); Algonquin (W. A. Nason). 



South Dakota: Harding Count v (S. S. Visher). 



Nebraska (Willy). 



Wyoming: Medicine Bow (F. M. Chapman). 



Oregon: (Amer. Mus. Nat. Hist. Coll.). 



Washington: Olympia (T. Kincaid); Pullman (W. M. Mann); 

 Paget Sound (Leconte). 



British Columbia: Vernon (W. H. Britton). 



I have described the female and male from specimens taken at 

 Pullman, Wash., by Mr. W. M. Mann. I have seen the nests of this. 



