SYSTEMATIC POSITION. 29 



Brown; thorax, scapes and legs somewhal paler; mandibles yellowish; apices of 

 the individual funicular joiiits blackish. 



Female (dcalated): Length 4.5-5 mm. 



Head, without the mandibles, but little longer than broad, with rather angular pos- 

 terior corners, straight, subparallel sides and straight posterior border. Eyes large and 

 rather convex. Mandibles and clypeus like that of the worker, scapes proportionally 

 shorter and stouter. Thorax large, as broad as the head, elongate elliptical, nearly 

 three times as long as broad. In profile the scutellum is very convex, projecting 

 above the meso- and epinotum. Epinotum with very short base and long abrupt 

 declivity. Petiolar node erect, more than half as broad as the epinotum. Gaster 

 elliptical, somewhat shorter and a little broader than the thorax. Legs slender. 



Sculpture like that of the worker but more opaque; mandibles and clypeus also 

 less shining. 



Scattered hairs more numerous than in the worker and also present in small numbers 

 on the vertex, gula, mesonotum, prosternum, and fore coxae. There is also a row of 

 short hairs along the j^osterior margin of each gastric segment. Pubescence dis- 

 tinctly longer, more silky, and denser than in the worker. 



Dark brown; antennae, legs and posterior margins of the gastric segments reddish; 

 mandibles, sutures of thorax and articulations of legs yellow. 



Hale: Length 2.8-3 mm. 



Head much flattened; including the flattened eyes, as broad as long. Vertex and 

 ocelli prominent. Cheeks short. Mandibles small, overlapping, with a single, acu- 

 minate apical tooth. Anterior clypeal border straight. Antennae slender; scape 

 only between three and four times as long as broad; first funicular joint globose, 

 broader than any of the other joints; second joint much longer than the "cape; joints 

 3-5 growing successively shorter; joints 6-12 considerably shorter and more slender. 

 Thorax very robust, elliptical, broader than the head, which is over-arched by the 

 protruding, rounded mesonotum. Scutellum even more prominent than in the female. 

 Epinotum with subequal base and declivity, the former slightly convex, the latter 

 feebly concave, forming an angle with each other. Petiole small, its node with rather 

 blunt margin, slightly inclined forward. Gaster very small, elongate elliptical, with 

 small rounded external genital valves. Legs slender. Wings with a four-sided discal 

 cell and two well develojjed cubital cells. The costal margin is depressed or folded 

 in just jiroximally to the stigma. 



Sculpture, pilosity and pubescence as in the worker; color more like that of the 

 female, except that the antennae, legs, mandibles and internal genitalia are pale, 

 sordid yellow. Wings smoky hyaline, with brown veins and stigma. 



I. humilis belongs to a small grouji of neotropical species embracing also I. iniquus 

 Mayr, dispertitus Forel, keiteli Forel and melleus Wheeler. The workers of keiteli and 

 melleus may be at once distinguished by their color, the former having a yellowish 

 brown head and thorax and the remaining parts brownish yellow; the latter being 

 pale yellow with a blackish gaster and funiculus. In these and in I. iniquus and 

 dispertitus the mesoepinotal constriction is much deeper than in humilis and the meso- 

 and epinotum are of a different shape. The mesonotum in profile does not form a 

 continuous, even line with the pronotum and the epinotum is very protuberant and 

 almost conical. /. humilis represents a transition from the above group of species 

 to that of /. analis Em. Andre, which is very common in the Southern States. This 

 species has a shorter, more robust thorax, more like that of Tapinoma, and much less 

 constricted in the mesoepinotal region. 



The above description was drawn from a number of workers, males and females 

 taken from the same nest in Baton Rouge, La., by Mr. Wilmon Newell. The types 

 described by Mayr were captured by Prof. P. de Strobel in the environs of Buenos 

 tAres. 



