SOCIAL LIFE OF WASPS 29 



showing how this is utilized in increasing the 

 family. The simultaneous nurture of a number of 

 offspring means more work, but it also means more 

 salivary juice, which is an elixir of life to the 

 mother-wasps. Roubaud's theory, perhaps an ex- 

 aggeration of a truth, is that the attractiveness of 

 this secretion has been the principal factor in the 

 social evolution of wasps. The nest has for its 

 "end," whatever that may mean, "a rational ex- 

 ploitation of the larvae," and its regime is such that 

 a constant supply of newborn wasp-babies is kept up. 

 For only the young larvae secrete the elixir. A 

 system of nutritive exchange (cecotrophobiosis it is 

 quaintly called) has been established, mothers and 

 children playing into one another's hands. Just as 

 tailor-ants use their children as needle-and-thread, so 

 these wasp-mothers obtain from their offspring 

 those luxuries which for animal as well as for man 

 often mean more than necessaries. 



It is hopelessly difficult for man to get mentally 

 into touch with wasps, for our lives and theirs are 

 run on quite different methods, which Sir Ray 

 Lankester has spoken of as the "little-brain" and 

 the "big-brain," the instinctive and the intelligent, 

 lines of evolution. Yet we venture to think that 

 further research will show that Dr. Roubaud's 

 theory is not altogether sound. We would suggest 

 that what he exaggerates into the main motive is 

 only the sop, the douceur, the encouragement, which, 

 organism being what it is, remains even unto the 

 end an exceedingly desirable stimulus of altruism. 



