INSTINCT 351 



for the exclusive good of another species, yet each tries 

 to take advantage of the instincts of others, as each takes 

 advantage of the weaker bodily structure of other species. 

 So again certain instincts cannot be considered as abso- 

 lutely perfect-, but as details on this and other such 

 points are not indispensable, they may be here passed 

 over. 



As some degree of variation in instincts under a state 

 of nature, and the inheritance of such variations, are in- 

 dispensable for the action of natural selection, as many 

 instances as possible ought to be given; but want of 

 space prevents me. I can only assert that instincts cer- 

 tainly do vary — for instance, the migratory instinct, both 

 in extent and direction, and in its total loss. So it is 

 with the nests of birds, which vary partly in dependence 

 on the situations chosen, and on the nature and temper- 

 ature of the country inhabited, but often from causes 

 wholly unknown to us: Audubon has given several re- 

 markable cases of differences in the nests of the same 

 species in the northern and southern United States. 

 Why, it has been asked, if instinct be variable, has 

 it not granted to the bee "the ability to use some other 

 material when wax was deficient"? But what other natu- 

 ral material could bees use? They will work, as I have 

 seen, with wax hardened with vermilion or softened with 

 lard. Andrew Knight observed that his bees, instead of 

 laboriously collecting propolis, used a cement of wax and 

 turpentine, with which he had covered decorticated trees. 

 It has lately been shown that bees, instead of searching 

 for pollen, will gladly use a very diflEerent substance, 

 namely oatmeal. Fear of any particular enemy is cer- 

 tainly an instinctive quality, as may be seen in nestling 





