ADAPTATIONS IN ANIMALS AND PLANTS 63 



it is well protected in some important ways against its enemies, 

 notwithstanding the fact that many individuals are sacrificed 

 in the egg and larval stages by parasites, and later on in Ufe, 

 by larger enemies. The tubercles and hairs of the larva, as 

 well as the markings, play an important part in protecting the 

 body against birds and Uzards. Moreover, the green larvae 

 are well protected when on their food plants, for I have 

 repeatedly observed how perfectly they blend against the leafy 

 background. There are undoubtedly other unknown factors, 

 besides those considered, which act in a beneficial way to pre- 

 serve the species. 



As to the variations noted in this species, I surmise that 

 the color varieties may be influenced by the larvse feeding on 

 diverse food plants, and the difference in the amount of nourish- 

 ment they obtain thereby. Then, too, there is the difference 

 in the temperature and humidity the species is subjected to, 

 as a result of covering such a wide range of territory. Pictet' 

 has shown in experiments on several moths, notably Ocneria 

 dispar, that by changing the food of the caterpillars of one or 

 two generations the moths showed great variations from the 

 normal forms in color and size. 



The wide distribution of the polyphemus moth seems to have 

 been brought about largely by the very fact of its adapta- 

 tion to many food plants, polyphagous habits, which would 

 faciUtate its adaptation to new fields. It is obvious that a 

 species Kving on many food plants would stand a much bet- 

 ter chance of being preserved than if its food were restricted 

 to one plant. 



Passing briefly in review, it is found that there is a series of 

 adaptations which begin in the egg and end in the adult moth. 

 Each stage has its special contentions independent of the others. 

 It is easily conceived that out of the hundreds of eggs laid 

 by this moth, comparatively few individuals, after escaping 

 parasitism, pass through the struggle of life and are able to 

 perpetuate the species. Yet in spite of the hazards encountered 

 during the egg, larval, and pupa stages the polyphemus is one 

 of our most common moths. Darwin ^ says in a letter to 



'Mentioned by Morgan, "Experimental ZoSlogy." 

 '"Life and Letters," p. 132. 



