1921] The Age of Insects 51 



districts of California, and how a new industry, absolutely depending 

 for its continuance upon a minute hymenopterous insect, was finally 

 established upon a firm and scientific basis. 



"How many cases of this kind exist among plants having no pre- 

 sent economic value it would be difficult to estimate, and how so com- 

 plicated a relationship ever became established is not yet explainable 

 even by a theory." (Smith). 



Fearing that I may weary you I am nevertheless impelled to point 

 out another ecological relation that borders upon the marvelous. I 

 refer to the relation between gall insects and their galls. We have here 

 another case of parallelism in evolution. The galls range from simple 

 folds of the leaf or simple enlargements of the stem to most elaborate 

 and wonderful structures and the insects themselves are scattered in 

 many orders. The most wonderful phase of the whole subject of galls 

 and gall makers is the fact that the galls are absolutely specific. It is 

 much easier to determine the gall maker by the gall that it makes than 

 it is by the insect itself. Just what are the factors that cause any 

 given cynipid gall, for example, to have the same form regardless of 

 what species of oak it is found on? Just what is the stimulus that 

 causes some galls to develop their form completely before the egg 

 hatches? In addition to these perplexing questions we have the whole 

 problem overlaid with the problem of parthenogenesis and alternation 

 of hosts we can appreciate that we have here a problem that demands 

 the best that any biologist can give. And the biologist who tackles 

 these problems may rest assured that the field is broad enough to de- 

 mand the best efforts that he can put forth. 



Conclusion 



Having considered briefly the past accomplishments in entomology 

 it may be worth our while to turn our attention in another direction 

 and ask ourselves what of the future. I do this because we are some- 

 what prone to think that all that is good, all that is worth while lies be- 

 hind us. Having lived through an age that has seen the development 

 of the automobile, the telephone, the aeroplane, wireless and half a 

 dozen other world astounding inventions we are inclined to think that 

 all the great inventions and discoveries have been made and that there 

 is little left to do. Which reminds me of a personal experience that 

 will perhaps make the matter clearer than anything else that I might 

 say. When I was a senior in high school I was told that for good and suf. 



