80 SLAVE-MAKING ANTS. 
carry off the pupe. 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. 
sanguimeas 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. sanguimeas 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. 
André says that they also make slaves of Formica 
gagates.. Schenk asserts? the same of Lasius alienus, 
and F. Smith of Z. flavus, but Forel denies these 
statements.? 
Another species, Polyergus rufescens, is much 
more dependent on its slaves, being, indeed, almost 
entirely so. 
' Rev. et Mag. de Zool. 1874, p. 164. 
2 Cat. of Brit. Foss. Hymen., p. 7. 
* Fowrmis de la Suisse, p. 363. 
