CELL-MAKINQ INSTINCT. 359 



fewer slaves, and in the early part of the summer extremely 

 few: the masters determine when and where a new nest 

 shall be formed, and when they migrate, the masters carry 

 the slaves. Both in Switzerland and England the slaves 

 seem to have the exclusive care of the larvte, and the mas- 

 ters alone go on slave-making expeditions. In Switzerland 

 the slaves and masters work together, making and bringing 

 materials for the nest; both, but chiefly the slaves, tend 

 and milk, as it may be called, their aphides; and thus both 

 collect food for the community. In England the masters 

 alone usually leave the nest to collect building materials 

 and food for themselves, their slaves and larvas. 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 P. sanguinea originated I 

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

 slave-makers will, as I have seen, carry oS the pupae of 

 other species, if scattered, near their nests, it is possible 

 that such pupse originally stored as food might become 

 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 pupte, 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-MAKIKG 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 its end, without enthusi^-stic admjratjon, We hear from 



