( cxxiii ) 



The cocoons of bifida are spun in the autumn, but the attack 

 did not take place for several months. The example is 

 probably typical in this respect. The procryptic preparation 

 of the autumn is the adaptation by which the average 

 numbers of the species are kept up in spite of ceaseless bark- 

 hunting during the months when the trees are leafless and 

 food is scarce. The Lamarckian interpretation fails to 

 account for the cocoon-making instinct for two very sufficient 

 reasons : first, a chrysalis is incapable of learning by experience 

 how to improve anything, — even more obviously incapable 

 of learning concerning a structure which it never makes. 

 Secondly, however intelligent a chrysalis may be, the experience 

 itself is of such a nature that its stores of learning cannot be 

 handed down to posterity.* 



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 beautifully-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 larvse, — studied with all the sympathy of 

 a born naturalist and described by a master of style, — have 



erroneously given as the year of issue instead of 1893. Some of the 

 later sentences of the same communication are also quoted with slight 

 modification on the present occasion. 



* This argument also is briefly stated in the "Proc. Boston Soc. Nat. 

 Hist.," vol. xxvi, 1894, p. 391, and quoted in "The Zoologist," Dec. 1900, 

 pp. 551, 552. 



