SOCIAL LIFE 245 



describes how in the larvae of some African species of 

 Pachysima (Fig. 62) there are on the ventral region of the 

 thoracic and first abdominal segments thin-walled finger- 

 like outgrowths in which fat- cells lie near the base while 

 the distal portion of the " exudatorium " contains the clear 

 fluid which, forced out through the body wall, can be 

 conveniently imbibed by the worker as she feeds the grub, 

 the grub's head being so situated as to be surrounded by 

 the curious outgrowths ; these become relatively smaller in 

 the later stages of larval life (Fig. 62, b, c) when the food 

 consists of pellets of insect fragments, the grubs in earlier 

 stages being fed on disgorged fluid. 



While the general behaviour of the members of ant 

 communities is mutually helpful, there are occasions when 

 individual self-assertion becomes evident. In times of 

 scarcity workers, especially the larger castes among poly- 

 morphic ants, may devour their comrades. Workers, short 

 of food, may eat grubs and pupae instead of tending and 

 protecting them. Between ants of different communities 

 or of different kinds there are various highly interesting 

 possibilities of relation. The driver or legionary ants 

 (p. 240 above) are as ready in their raids to prey upon other 

 ants as on cockroaches, grasshoppers, spiders, or vertebrates. 

 " Certain small but aggressive ants,'* writes Wheeler, 

 " which secure at least a portion of their sustenance by way- 

 laying the foraging workers of another species and snatching 

 away their food, deserve the name of brigands. Such ants 

 naturally make their nests near those of the species they 

 plunder." Some predaceous species raid the nests of more 

 pacific ants, kill adults and carry off larvae and pupae to 

 serve as food. From such habits as this has arisen, in the 

 opinion of Wheeler and others, the oft- described " slave- 

 making " of Formica sanguinea which ranges over all the 

 north temperate regions of the globe, its societies harbouring 

 a number of workers of the allied F. fiisca. From estab- 

 lished communities the sanguinea workers go forth to raid 

 nests of fusca whence they bring back grubs and pupae, 

 some of which are not killed, but preserved to grow into 



