80 SLAVE-MAKING ANTS. 



carry off the piipoe. When the latter come to maturity 

 they find themselves in a nest consisting partly of F. 

 sanguineas, partly of their own species, the results of 

 previous expeditions. They adapt themselves to cir- 

 cumstances, assist in the ordinary household duties, 

 and, having no young of their own species, feed and 

 tend those of the F. sanguineas. But though the F. 

 sanguineas are thus aided by their slaves, or as they 

 should rather perhaps be called, their auxiliaries, they 

 have not themselves lost the instinct of working. It 

 seems not improbable that there is some division of 

 functions between the two species, but we have as yet 

 no distinct knowledge on this point ; and at any rate 

 the F. sanguineas can ' do ' for themselves, and carry 

 on a nest, if necessary, without slaves. 



The species usually enslaved by F. sanguinea are 

 Formica fusca and F. rufibarbis, which indeed are so 

 similar that they are perhaps varieties rather than 

 species. Sometimes both occur in the same nest. 

 Andre says that they also make slaves of Formica 

 gagates} Schenk asserts^ the same of Lasius alienus, 

 and F. Smith of L. fiavus, but Forel denies these 

 statements.^ 



Another species, Polyergus rvjescens, is much 

 more dependent on its slaves, being, indeed, almost 

 entirely so. 



' Bcv. et Mag. de Zool. 1874, p. 164. 

 "^ Cat. of Brit. Foss. Hymen., p. 7. 

 ' Fourmis de la Suisse, p. 363. 



