432 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
F. aggerans is undoubtedly the common “thatching ant” of the 
Western States. It constructs a nest very much like that of F. rufa 
pratensis in Europe, at altitudes varying from 6,000-8,000 ft. The 
vegetable débris used in the construction of the mounds is often very 
coarse. McCook mentions this ant or possibly the true obscuripes 
as occurring at Iowa Gulch near Leadville, Colo., at an elevation of 
11,300 ft. 
28. F. RUFA AGGERANS var. MELANOTICA Emery. 
F. rufa obscuriventris var. melanotica Emery, Zool. jahrb. Syst., 1893, 7, p. 
644, 650, 8 ; 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 
aggerans, but the pubescence on the gaster 1s more dilute, so that this. 
region is more shining and the shagreened surface is visible. 
FremaLe. 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. 
Mae. 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 County (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);: 
Puget 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. 
