THE SANGUINARY ANTS. 



455 



least when living in large colonies, assails any intruder with its 

 mandibles, simultaneously turning the tip of its gaster forward and 

 injecting formic acid into the wound. F. sanguined is, to use Was- 

 mann's expression, a facultative slave-holder, for it sometimes lives in 

 independent, slaveless colonies. As it has lost none of its essential 

 formicine instincts, it is able to excavate a nest, secure its own food 

 and bring up its own young without the aid of slaves. But even when 

 these auxiliaries are present, much, if not most, of the labor of the 



FIG. 267. The typical Formica sanguined of Europe. (Original.) a, Dealated fe- 

 male; b, pseudogyne; c, worker; d, head of same, showing the notched clypeus. 



colony devolves on the sanguined, and there is nothing to show that the 

 slaves contribute anything more to the communal activities than would 

 be contributed by an equal number of small sanguined workers. 



The normal slaves of F. sanguined are members of the F. fitsca 

 group, namely, fused, glcbaria, rubcscens, gagatcs, rufibarbis and 

 cincrca, but it occasionally enslaves members of the rufa group (rufa, 

 pratcnsis and their varieties). Wasmann (19020) has published sta- 

 tistics of 410 sanguined colonies found nesting within an area of 4 sq. 

 kilom. in Holland. In this region the ratio of slave-containing to 

 slaveless colonies was as 40 : i ; that of colonies containing the normal 

 slaves (fused, rufibarbis ) to those with pratensis and rufopratensis as 

 78.6: i ; and that of the nests containing fused only, rufibarbis only or 

 both of these forms as 70.5 : 3. There can be no doubt that the typical 

 fitsca is the form most frequently enslaved in northern Europe and at 



