( cxx ) 



cavities, and svibject to the pressure of muscular body-walls. 

 Hence an insignificant injury may often cause death or imper- 

 fect development from the quantity of fluid which is lost. 

 " It is, I believe, in consequence of these facts that the various 

 means of protection in larvse are almost always of a passive 

 kind. . . . Nearly all the means of defence against . . . 

 enemies [other than ichneumons, etc] are such as tend to 

 prevent the larva from being seen or touched, rarely such as to 

 be of any avail when actually attacked. There may be various 

 changes in the mode of defence, but the object is always the 

 same — to leave the larva untouched, a touch being practicallj 

 fatal." * 



Let us consider for a moment the mental operations involvel 

 in the act of profiting by experience. Consider, for instancy 

 Mr. A. H. Hamm's interesting observation^ — since abundant^ 

 confirmed by the testimony of many naturalists — that the vat 

 majority of the individuals of Hyhernia leucophaearia rest wih 

 the body horizontal, thus bringing the lines of the wings ino 

 parallelism with the dark shadows in the vertical cracks of tie 

 oak-bark. t An individual which adopted a different attitule 

 and rested so as to cause the main lines of its pattern to (^t 

 the main lines of its environment might indeed escape fy 

 flight ; but can any one really believe that a moth, or anyDf 

 the ancestors of moths, could associate the special disturbace 

 and danger to which it had been exposed with the specal 

 attitude it had assumed, and would as a result of that ass(ii- 

 tion begin to make changes in its attitude ? It is easy bo 

 speak of improvement by experience, perhaps easy to thinkof 

 the progress of an insect's education under the sternest t)f 

 teachers : easy so long as we confine ourselves to generalitis. 

 Attempt to picture the process in a definite case, and apply it,i,s 

 I have done, to account for the growth of some special protectre 

 adaptation, and it is instantly borne in upon us that we SQ 

 placing on insect psychology a load it is altogether unable jO 

 bear. \ \ 



The Cocoon-mahing Instinct. — There are however number- 

 less examples in which it is impossible that improvement couldj 



* Trans. Ent. Soc, London, 1885, pp. 321-323. 

 t Proc. Ent. Soc. Lond. for March 19, 1902, p. xv. 



