IN THE SHETLANDS 181 
the whole community would be, if “a divided duty ” 
claimed their attention. 
It is not at all necessary to show that the socialism 
of insects has advanced along these lines—their 
greater fertility allowing of a still more remarkable 
specialisation—in order to make out a case for the 
possibility, or even likelihood, of its hereafter doing 
so in the case of some birds. There are insect com- 
munities, however, composed of males and fertile 
females, or of the latter only, that may be compared, 
without much violence, to those of terns or weaver- 
birds. There are the mason-bees, for instance— 
numbers of whom labour side by side, each at making 
its own nest, in which, perhaps, we see an early state 
of our more truly social hymenoptera. But in nature 
many ways constantly lead to the same goal, and what 
this is, or is likely to be, must depend on the kind of 
advantages which the general conditions prescribe and 
make possible. It is difficult in the case of animals, 
no less than in that of man, to imagine any great 
social advance except through, or side by side with, 
subdivision of labour ; and for real social labour to be 
subdivided, it must first be extended, that is to say in 
common. The separate attention paid by each pair 
of birds in a community to its own young only is 
not subdivision of labour in the proper socialistic 
sense of the term; for this labour is not social, but 
solitary. It appertains, that is to say, to every 
solitary-breeding animal, or, if not to both parents, at 
least to one, so that, at best, we do not get beyond 
