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 larve,” and its régime is such that 
a constant supply of newborn wasp-babies is kept up. 
For only the young larve 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. 
