472 bulletin: museum of comparative zoology. 



thick below, with very sharp upper border and straight anterior and 

 posterior surfaces. The erect, silvery white hairs covering the body, 

 legs, and antennal scapes are longer and more abundant. The pu- 

 bescence is very fine and sparse on the gaster so that this region is very 

 smooth and shining. The mesonotum is not spotted but, together 

 with the scutellum, paraptera, and metanotum, uniformly dark l^rown 

 and rather sharply marked off from the remaining paler portions of 

 the thorax, which are brownish red. Occiput slightly infuscated. 

 Gaster very dark brown, anal region red. Wings grayish hyaline, 

 with brown veins and stigma. 



Nevada: Ormsby County, July 1903 (C. F. Baker). 



Although this form is readily distinguished from the females of all 

 the forms of microgyna by its very smooth gaster, more material may 

 show that it is to be regarded as a subspecies of microgyna and not as 

 an independent species. 



59. F. impexa Wheeler. 



F. impexa Wheeler, Bull. Amer. mus. nat. hist., 1905, 21, p. 273, S ; Psyche, 

 1906, 13, p. 40, 9 ; Ants, 1910, p. 570. 



Worker. Length 3.3-6 mm. 



Resembling F. microgyna. 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, with straight posterior and straight, 

 subparallel lateral borders. Joints 1-4 of funiculi decidedly longer 

 and more slender than the penultimate joints. Maxillary palpi rather 

 short. Thorax with the epinotum low and much rounded, without 

 distinct base and declivity, mesoepinotal constriction rather narrow 

 and shallow, pro- and mesonotum moderately convex. Petiole nar- 

 row, cuneate in profile, its anterior surface convex, its posterior surface 

 flat, its border moderately sharp and produced upward in the middle. 

 In small workers the edge may be much more blunt. 



Mandibles lustrous, finely and sharply striated. Surface of clypeus 

 uneven. Frontal area smooth and shining. Remainder of body 

 opaque, finely but distinctly shagreened. 



Whole body and appendages clothed with very minute white pubes- 

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

 concealing the ground surface of the gaster. Body, antennal scapes 

 and legs covered with short, coarse, obtuse, erect or suberect, whitish 

 or yellowish hairs. On the gaster these are uniformly distributed 

 and in certain lights very conspicuous, but shorter than in the various 

 forms of microgyna. They are also very numerous and prominent 



