TRANSMISSIBILITY OF FUNCTIONAL MODIFICATIONS 95 



course of the phylogeny. without the co-operation of the Lamarckian 

 factor. I have not hitherto laid any special emphasis upon the degree 

 of differences occurring between workers and queens ; but I must 

 now add that this may far exceed the degree that we are familiar 

 with in our common indigenous ants, both in regard to instinct and 

 to bodily form. Even in the red Amazon ant of Western Switzerland, 

 Polyergus rv/escens, we find quite a new instinct', that of carrying off 

 the pupas of other species of ants, not to devour, but to introduce them 

 to their own nest and tlius secure ' slaves.' For these workers of 

 a strange species, which emerge in a strange nest, naturally regard the 

 place of their birth as their home, and do there what instinct 

 impels them, and what they would have done in the nest of their 

 parents : they feed the larvas, fetch food, collect building material, 

 and so on. The domestic activity of the workers of the master- 

 species thus becomes superfluous, and they have ceased to exercise it, 

 and have now entirely lost the power of caring for their brood, searching 

 for food, and keeping up the nest. They have even forgotten how 

 to take food themselves, because they are always fed by the ' slaves.' 

 Forel informs us — and I have myself repeated the experiment — that 

 Polyergus workers, which are shut up with a drop of honey on the 

 floor of their prison, will leave it, their favourite food, untouched, 

 and finally starve, unless one of their ' slaves ' be shut up with them. 

 As soon as this happens, and the slave perceives the honey, it j^artakes 

 of it, and then the ' mistress ' comes and strokes the ' slave ' with her 

 antennae to signify her desires, whereupon the ' slave ' proceeds to feed 

 her from its own crop. 



But while the Polyergus workers have forgotten their domestic 

 habits, and have even ceased to be able to recognize their food, 

 remarkable changes have taken place in their jaw^s ; these have lost 

 the blunt teeth on the inner margin, which, in other species, serve for 

 masticating the food, for seizing building material, and for other 

 domestic occupations, and have become sharp weapons, bent in the 

 form of a sabre, very well suited for piercing the head of an enemy, 

 but also well adapted for carrjang oft' the pupre, because they can 

 seize them withovit doing them any injury. 



No one wall doubt that the predatory expeditions of the Amazon 

 ants, and the slave-making habit, can only have developed after the 

 habit of living in large companies had long existed, and this case 

 proves that variations of instinct, as well as of bodily structure, can 



* 'New' in this sense, that the instinct is not exhibited by most worker-ants, that 

 it did not occur in the primaeval ancestors of modern ants. It is, however, exhibited 

 by a number of modern forms, and even by some German species. 



