92 THE LAW OF BIRTHS AND DEATHS 



in captivity will be much more pronounced and of longer 

 duration. They will be reduced to a life of the utmost 

 inactivity and well and regularly fed upon rich foods. 

 It will take a long time for an animal's system to adapt 

 itself to such a change. 



Darwin gives a number of instances showing that insects 

 are also liable to show diminished fertility as a result 

 of confinement. But the most remarkable support is 

 given to the theory by the cases of ants and bees. It 

 is surely no mere coincidence that the most conspicuous 

 examples of cerebral development and nervous energy 

 throughout the insect world should be almost wholly 

 sterile, and that the fertile members of the ant and bee 

 communities are conspicuously deficient in those intel- 

 lectual attributes for which their sterile relatives are 

 famous. It is an established fact that a fertile, big-bodied, 

 and sluggish queen, or an infertile, small-bodied, and 

 active worker may be developed at the will of the nurse 

 bees from the same fertilised egg if taken within a few 

 days of being laid. All the larvse are fed upon the same 

 milk-like pap for the first three days or so, but after that 

 the workers are weaned and placed on sparser and plainer 

 diet. Those intended for queens, however, are fed 

 sumptuously on the original brood food, under the stimulus 

 of which they grow much bigger than the workers and 

 develop an enormous fertility. But what they gain in 

 size and fertility they lose in energy and brain develop- 

 ment. The workers, reared on a diet of honey and pollen, 

 develop great brain power and energy, but what they 

 gain in these directions they lose in size and fertility. 

 We shall see later that these facts are paralleled by similar 

 facts in the human race, and we have already seen a some- 

 what similar example in the case of mountain sheep. 

 But it is necessary to point out that sterility in the case 



