INSTINCT 869 



their aphides; and thus both collect food for the com- 

 munity. In England the masters alone usually leave the 

 nest to collect building materials and food for themselves, 

 their slaves and larvae. So that the masters in this 

 country receive much less service from their slaves than 

 they do in Switzerland. 



By what steps the instinct of F. sanguinea originated 

 I will not pretend to conjecture. But as ants which are 

 not slave-makers will, as I have seen, carry off the pupae 

 of other species, if scattered near their nests, it is possi- 

 ble that such pupae originally stored as food might be- 

 come developed; and the foreign ants thus unintentionally 

 reared would then follow their proper instincts, and do 

 what work they could. If their presence proved useful 

 to the species which had seized them — if it were more 

 advantageous to this species to capture workers than to 

 procreate them — the habit of collecting pupae, originally 

 for food, might by natural selection be strengthened and 

 rendered permanent for the very different purpose of 

 raising slaves. When the instinct was once acquired, if 

 carried out to a much less extent even than in our 

 British F. sanguinea, which, as we have seen, is less 

 aided by its slaves than the same species in Switzerland, 

 natural selection might increase and modify the instinct — 

 always supposing each modification to be of use to the 

 species — until an ant was formed as abjectly dependent 

 on its slaves as is the Formica rufescens. 



Cell-making instinct of the Hive- Bee. — I will not here 

 enter on minute details on this subject, but will merely 

 give an outline of the conclusions at which I have 

 arrived. He must be a dull man who can examine the 

 exquisite structure of a comb, so beautifully adapted to 



i 



