PROTECTIVE RESEMBLANCE IN 

 THE INSECTA. 



I. TJic tJicory of Natural Selection. 



The theory of the origin of species by means of natural 

 selection, first brought before the scientific world by Charles 

 Darwin more than 40 years ago, is now more or less 

 familiar to all biologists. It is based upon a few well 

 known facts ; ist, that the offspring of all animals and 

 plants are more numerous than the parents : 2nd, that 

 there is no proportionate increase in numbers of living 

 things which reach maturity: 3rd, that variations from 

 the parental forms occur in the young. 



Briefly stated, the theory is that the increase in the 

 numbers of young, whilst the total number of adults 

 •remains practically stationary, shows that a continual 

 contest takes place for existence ; that those individuals 

 who vary in a direction which is best adapted to the 

 struggle for life, are the most likely to survive, and that 

 the hereditary transmission of favorable variations, with 

 changing conditions of life, lead to structural modifications 

 and to the evolution of new species. 



The young of each generation are always much more 

 numerous than the parents, in all orders, classes and 

 families throughout the animal and vegetable kingdoms. 

 There is consequently a rapid and continuous increase in the 

 numbers brought into existence. Some plants are much 

 ;more prolific than others, but whatever the proportions 



