1907.] Wheeler, Fungus-growing Ants of North America. 717 



ures 3 mm. in length and has no reentrant notch between the anterior lobular 

 and posterior ridge-like portions of the frontal carin?e, and the shape of the 

 thorax appears to differ considerably from that of hartmanni. Emery, to 

 whom I sent some workers of this latter form, says, however, that both 

 species "connetano tra loro i generi Aita e Cyphomyrmex; e dubbio a quale 

 dei due convenga meglio assegnarli." As I shall show in the latter part of 

 this paper, the habits of hartmanni are much more like those of Trachymyr- 

 mex than Cyphomyrmex, so that the subgenus Mycetosoritis, which I have 

 erected for this species and aspera ^layr, belongs rather with Atta s. lat. M. 

 hartmanni should be regarded as the type of this subgenus as Mayr's species 

 is so imperfectly known. 



10. Atta (Mycocepurus) smithi Forel. 



Atta (Mycocepurus) smithii Forel, Trans. Ent. Soc. London. 1893, p. 370. $. 



Worker. (PI. XLIX, Figs. 1.5 and 16.) Length: 2.2-2.-5 mm. 



Head, without the mandibles, slightly longer than broad, a little broader in 

 front than behind, with obtusely excised posterior border, pointed posterior corners 

 and rather convex sides. There is a distinct though shallow occipital groove. Eyes 

 moderately convex, just behind the middle of the head. Mandibles narrow, acute, 

 with oblique, 5-toothed blades. Clypeus short and broad, with entire, nearly 

 straight anterior border. Frontal carinse with small rounded lobes, A^ery close to- 

 gether and separated only by a narrow, cuneate groove; they are continued behind 

 as low diverging ridges which fade away before reaching the posterior corners. 

 Postorbital carinse indistinct, reaching the posterior corners but not including with 

 the frontal ridges distinct grooves for the accommodation of the antennal scapes. 

 Scapes much shorter than the funiculi, slightly thickened towards their tips, which 

 barely surpass the posterior corners of the head. Thorax long, in front about 5 as 

 broad as the head, with deep mesoepinotal constriction. Pronotum without inferior 

 spines, above with four upwardly directed spines arranged in an arc with its convexity 

 directed forward; the two outer spines longest and each with a small acute tooth in 

 front of its base; the inner pair of spines small. Mesonotum also wth an arc of four 

 spines but with its convexity directed backward, so that the spines on both segments 

 form a broad ellipse. The anterior meso thoracic spines are longer than the posterior 

 pair. There is also a pair of small projections close together near the anterior borders 

 of the mesonotmn and in the middle of the ellipse. Epinotum with the base fully 

 twice as long as the declivity, the former with four successive pairs of spines, the 

 first and third very short and acute, the second longer and the fourth, representing 

 the typical epinotal spines of other Attii, fully as long as the declivity, slender, 

 pointed, directed upward and slightly backward and outward, curved inward at 

 their tips. Metastemum with a small blunt tooth on each side. Petiole from above 

 narrow, fully twice as long as broad, somewhat violin-.shaped, broader behind than 

 in front, constricted just in front of the node which is cuboidal, with a concave sur- 

 face and each of the four upper comers produced into a small spine. In profile its 

 upper surface is horizontal, its anterior slope long and concave. Postpetiole nearly 

 four times as broad as the petiole and nearly as broad as long, cam])aiiulate, with 



