CHAP. VIII. 1 CELL-MAKING INSTINCT. 205 



and the masters alone go on slave-making expeditions. In Switzer- 

 land 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 larvaj. So that the masters in this country receive much 

 less service from their slaves than they do in Switzerland. 



By Avhat 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 possible that such pupse originally stored as 

 food might become developed ; and the foreign ants thus uninten- 

 tionally 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. san- 

 guinea, 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 its end, without enthusiastic admiration. We hear 

 from mathematicians that bees have practically solved a recondite 

 problem, and have made their cells of the proper shape to hold the 

 greatest possible amount of honey, with the least possible con- 

 sumption of precious wax in their construction. It has been 

 remarked that a skilful workman with fitting tools and measures, 

 would find it very difficult to make cells of wax of the true form, 

 though this is effected by a crowd of bees working in a dark hive. 

 Granting whatever instincts you please, it seems at first quite 

 inconceivable how they can make all the necessary angles and 

 planes, or even perceive when they are correctly made. But the 

 difficulty is not nearly so great as it at first appears : all this 

 beautiful work can be shown, I think, to follow from a few simple 

 instincts. 



I was led to investigate this subject by Mr. Waterhouse, who 

 has shown that the form of the cell stands in close relation to the 



