SLAVES AND SLAVE-MAKERS. 



4. Petiole broad, with sharp upper border; body and 

 lower surface of head without erect hairs 



F. truncicola Integra. 



Petiole narrow, thick, and blunt above 



F. difficilis consocians. 



5. Middle funicular joints more than one and a half 

 times as long as broad; scape very slender and nearly 

 straight; petiole with convex anterior and posterior sur- 

 faces, and blunt upper margin; body smooth and rather 

 shining F. pallide-fulva. 



Middle funicular joints usually less than one and a 

 half times as long as broad; scape distinctly curved at 

 base; posterior surface of petiole flat; body more densely 

 pubescent F. fusca. 



F. sanguined usually nests under stones in grassy places 

 along the edges of woods. It obtains slaves, or auxiliary 

 workers, by kidnapping the larvae and pupas of fusca 

 subsericea. 



F. exsectoides occurs chiefly in the Alleghanies. It 

 nests in and under mounds which it constructs of earth 

 and vegetable debris. Not only are these mounds often 

 three or four feet in diameter and a foot or two high, but a 

 single colony often extends over several mounds. The 

 females get a start by establishing their colonies in de- 

 pauperate colonies of fusca subsericea. It feeds partly, 

 at least, on dead insects. 



F. truncicola integra is our largest and most conspicuous 

 form of truncicola. The nests are in piles of large stones or 

 in old logs and stumps; they are stuffed with bits of grass 

 and leaves. Like most other species of Formica, integra 

 is much given to attending aphids. It is most abundant 

 in hilly regions, where it prefers clearings in the forests. 



The females of F. difficilis consocians, which are yellow 

 and hardly larger than the largest workers, are temporary 

 parasites in the nests of schaufussi var. incerta. Soon after 

 fertilization the queen seeks adoption in some depauperate 

 and probably queenless colony of incerta and there permits 

 her hosts to bring up her young. Later the incerta workers 

 die off, leaving the consocians as a pure and independent 

 colony, which grows rapidly in size and shows no evidence 



423 



