PROVIDENT IMPULSES 81 



Acquisitiveness is the most elementary of the 

 human impulses that fall into this group. Apart 

 from man, very few mammals make stores of 

 food. Amongst some birds, as those of the crow 

 tribe, there is a curious development of a passion 

 for hoarding. But we have to descend to the 

 insects to find illustrations of such a desire to 

 appropriate as urges human industry. There 

 are species of ants which have enslaved other 

 ants, and keep, as milch cows, the minute insects 

 known as " aphides." Constructiveness is dis- 

 played in every class of the animal kingdom. 

 Some minute unicellular protozoa (Foraminifera 

 and Radiolaria) construct shells of marvellous 

 delicacy and beauty : zoophytes have their corals, 

 molluscs their shells : fish and birds make nests : 

 the larva of the caddis-fly protects itself with a 

 mantle of sand and fibre. Curiously enough this 

 impulse influences mammals but little, and in this 

 class, apart from man, there are few animals that 

 construct themselves a house. Its importance in 

 human development needs no illustration. In- 

 genuity has taught man how to domesticate 

 animals, has endowed him with the art of agri- 

 culture, and has enabled him to make tools and 

 machines which, commencing with the stone axe, 

 have culminated in the aeroplane. But man owes 

 to this group of impulses his avarice, covetous- 

 ness, and propensity to overreach his fellows. 



We shall see that the reproductive and pro- 

 vident instincts are in some measure antithetical : 

 one gains strength as the other loses it. There is 

 a curious illustration of this contrast in the loss 

 of sex by those bees which are specially charged 

 with the construction and management of the hive. 



