INSECTS IN RELATION TO OTHER ANIMALS 231 



pest. Witness the maple bark louse, which is so rare in natural forests 

 as scarcely ever to be seen, limited there as it is by its feeble locomotive 

 power and the scattered situation of the trees it infests. With the multi- 

 plication and concentration of its food in towns, it has increased enor- 

 mously, and, if it has not done the gravest injury, it is because the trees 

 attacked by it are of comparatively slight economic value, and because 

 it has finally reached new limits which hem it in once more. 



" We are therefore sure that the destruction of any species of insectivo- 

 rous bird or predaceous insect is a thing to be done, if at all, only after 

 the fullest acquaintance with the facts. The natural presumptions are 

 nearly all in their favor. It is also certain that the species best worth 

 preserving are the mixed feeders and not those of narrowly restricted 

 dietary (parasites, for instance) , that while the destruction of the latter 

 would cause injurious oscillations in the species affected by them, they 

 afford a very uncertain safeguard against the rise of such oscillations. 

 In fact, their undue increase would be finally as dangerous as their 

 diminution. 



" Notwithstanding the strong presumption in favor of the natural 

 system, when we remember that the purposes of man and what, for con- 

 venience' sake, we may call the purposes of Nature do not fully harmo- 

 nize, we find it incredible that, acting intelligently, we should not be able 

 to modify existing arrangements to our advantage, especially since 

 much of the progress of the race is due to such modifications made in the 

 past. . . . 



"But far the most important general conclusion we have reached is a 

 .conviction of the general beneficence of nature, a profound respect for 

 the natural order, a belief that the part of wisdom is essentially that of 

 practical conservatism in dealing with the system of things by which we 

 are surrounded." 



Efficiency of Protective Adaptations of Insects. Interesting 

 from a scientific point of view are the various adaptations by means of 

 which insects are protected more or less from their bird enemies. Color- 

 ational adaptations having been discussed in another chapter, there 

 remain for consideration (i) hairs, (2) stings, (3) odors, flavors and 

 irritants. Most of what follows is from an admirable paper by Dr. Judd, 

 whose data are based upon his examination of the stomach contents of 

 fifteen thousand birds. 



Hairs. " Excepting two species of cuckoos, no species of bird in the 

 eastern United States, so far as I am aware, makes a business of feeding 

 upon hairy caterpillars." Judd observed that Hyphantria cunea infest- 



