THE WEB OF LIFE 347 



males and females usually in the proportion of 7 : 1, though 

 sometimes there are still fewer females. It is said that 

 these spiders sometimes work together, e.g. in securing a 

 victim, and that they share the food without quarrel. 

 There is no marked dimorphism of the sexes, which live 

 together amicably — in a sort of millennium among spiders. 

 The maternal care is very highly developed. 



(2) Another diagnostic feature is the existence of division 

 of labour, implying some measure of mutual dependence. 

 The different types in the ant-hill, the termitary, and the 

 bee-hive are the best illustrations, but we see the same 

 ' idea ' in the posting of sentinels, which is well known 

 among both birds and mammals — ^witness, for example, 

 rooks and monkeys. 



(3) In some cases we seem to be warranted in speaking 

 of social conventions. Thus in. certain species of ants it 

 appears to be the unwritten law that the full must not refuse 

 to feed the hungry, and in a rookery it seems to be an estab- 

 lished convention that after a nest has reached a certain 

 stage in its construction it is no longer legitimate to steal 

 sticks from it. 



In connexion with the origin of animal societies there is 

 probably a hint to be got from the occurrence of temporary 

 sociahzations. We get an illustration of this when migrat- 

 ing birds form a company — sometimes relatively small, as 

 when the V-shaped band of wild geese passes ' honk-honk- 

 ing ' overhead ; sometimes innumerable, as when vast 

 flocks of plover pass southwards in the autumn. Tinother 

 illustration may be found in the march of the lemmings 

 when they are compelled by over-population and the conse- 

 quent dearth of food to leave their homes ; and it is inter- 

 esting to notice what audacity and persistence the force of 



