1 68 WILLIAM MORTON WHEELER. 



widely separated. Mandibles well-developed but narrow, their 

 long apical borders finely denticulate. Antennae slender, the 

 scapes extending well beyond the posterior border of the head. 

 Thorax large, the mesonotum convex anteriorly, with distinct 

 Mayrian furrows. Scutellum trapezoidal, nearly as long as 

 broad, feebly impressed in the middle, with entire posterior 

 border. Petiole and postpetiole similar to those of the worker but 

 the former more pedunculate anteriorly. Gaster small, oval; legs 

 long and slender, the femora feebly bent. 



Surface of the body smoother than in the worker and female, 

 the mandibles and gaster somewhat shining, the remainder of the 

 body subopaque. 



Pilosity and pubescence very short and meager, only the sides 

 of the petiole and postpetiole with tufts of hairs like those of the 

 worker and female. Antennae and legs destitute of hairs, with 

 fine, indistinct pubescence. 



Brownish yellow, head, a spot on the posterior portion of the 

 mesonotum and a line on each side of it, brown. Wings colored 

 as in the female. 



Described from numerous workers, five females and a male 

 taken on Barro Colorado Island, C. Z. during late July and early- 

 August. 



This form is so close to 5. impexus of British Guiana that it 

 might be regarded as a subspecies. I have given it specific rank, 

 however, because it now appears that there are several forms 

 impexus Wheeler, urichi Forel, diego Forel, morierai Santschi, 

 lutzi Wheeler, zacapanus Wheeler, opacus Mayr, pusillus Forel 

 and aztecus Forel which are so closely related that they may be 

 merely geographical races, or subspecies of one or a few highly 

 variable species. At present our knowledge of these various 

 forms and of their phases is so meager that it seems best to regard 

 them as specifically distinct. 



Megalomyrmex (Cepobroticus Subgen. nov) symmetochus sp. nov. 



(Fig. 5-) 



Worker. Length 3-3.5 mm. 



Head subrectangular, very slightly narrower behind than in 

 front, with straight posterior and very feebly convex lateral 



