160 INSECTS AND HEREDITY 



If the Lamarckian interpretation of the cocoon-making 

 instinct must inevitably fail, as I think we shall agree it 

 must, what is there to put in its place ? Those who 

 believe in the efficiency of Natural Selection in evolution 

 will probably regard the instinct of building these beauti- 

 fully-adapted structures as the outcome of countless 

 generations during which the attacks of enemies have 

 been, on the whole, more successful against the products 

 of less perfected instincts and less so against those of 

 the more perfected. They will further suppose that the 

 increasing perfection in instinct has acted selectively on 

 enemies, sharpening their faculties, until, by action and 

 reaction, the present high level of constructive skill has 

 been reached, and is maintained. 



The Instincts of the Hymenoptera. 



No discussion of instinct would be in any way complete 

 without a consideration of the most wonderful examples 

 of all, viz. those manifested by the Hymenoptera. The 

 instincts of the Fossorial Aculeates in providing for their 

 larvae — studied with all the sympathy of a born natura- 

 list and described by a master of style — have formed 

 the foundation of a gigantic speculative edifice. The 

 controversy has in reality been a three-sided one. 



I. First, we have Fabre disbelieving in evolution alto- 

 gether, and adducing evidence that his favourite insects 

 have not gained their wonderful instincts by progressive 

 change, pointing out that they perform their duties under 

 some stimulus which to them is imperative, whether the 

 object of their pains be achieved or not : arguing, for 

 example, that in those that feed their larvae from time to 

 time, the stimulus to enter and deposit the insect food is 

 not the young larva itself but the door of the tunnel. 



II. Secondly, Lord Avebury and the late George J. 

 Romanes have argued in favour of evolution by a gradual 

 education, finally inherited as instinct. There is reason 

 to believe that Darwin accepted the same view. He 

 certainly never opposed it. Lord Avebury alludes to the 



Hist., vol. xxvi, 1895, p. 391 (reprinted on pp. 117, 118 of this volume), 

 and quoted in The Zoologist, Dec. 1900, pp. 551, 552. 



