ARMY ANTS IN BRITISH GUIANA. 



315 



or piceous and the legs are somewhat paler than in hcchci. In both 

 varieties the polymorphism of the worker is less pronounced than ia 

 the typical pilosum. 



Turning to the male we find that it is merely a variety of Eciton 

 mexicanum Smith, a form easily recognized by the peculiar shape of its 

 mandibles (Fig. 7a). Smith described the worker as Eciton pilosum 

 from Brazil in 1858, and the male as Labidus mexicanus from Orizaba, 

 Mexico in 1859. Of the male Forel has described a var. aztecum from' 

 Guatemala and a subsp. rosenbergi from Northwestern Ecuador. 



Figure 7. (a) Head of male E. (A.) -pilosum F. Sm. (in sp.); {h) head of 

 male Eciton {Acamaius) pilosum F. Sm. var. beebei var. nov. 



That the typical mexicanum is the male of the typical pilosum (worker) 

 is evident from the fact that both of these forms, and only these, 

 occur in Texas. The male of the var. beebei measures 10.5-11 mm. and 

 is therefore decidedly smaller than the male of the typical form of 

 the species, which measures nearly 13 mm., and exhibits also the fol- 

 lowing differences: Ocelli smaller, head seen from above proportion- 

 ally longer; frontal carinse distinctly more acute, with their posterior 

 ends more sharply dentate. Antennae shorter. Thorax proportion- 

 ally longer and more slender, with less elevated scutellum. Color 

 more yellowish, with the posterior part of the head jet black; sub- 

 genital plate, posterior border of each gastric segment and the funi- 



