41 



eventnallv siiy)plaiiT the parent species, whether it be sterile 

 with it or not. 



Komanes placed verv little stress upon morphological isola- 

 tion, bnt he did not consider the case of the aedeag'i of insects. 

 This form of isolation, which we ma}' term ''phalic", is of such 

 great importance that it will have to be given an important posi- 

 tion in the final consideration of evolution. How far the steril- 

 ity of allied species is due to "physiological" and how far to 

 ''phalic" isolation is a matter to decide by experiment. 



Of the various problems that confront the student of insect 

 evolution, none is more difficult than that presented by the male 

 genital structures. It has been recognized for a long time that 

 these sructures present the most definite characters upon which 

 to base the species in many groups of insects. In many cases 

 this is the reason to believe that correlated structures exist in 

 the opposite sex, and this further complicates the problem. An 

 organ of such vital importance to the life of the species must 

 have been functionally adequate from the earliest period of in- 

 sect physiology, so that it is highly improbalile that a series of 

 slight variations, each more advantageous than the former, could 

 have been preserved by natural selection ; still more improbable 

 that a corresponding series of changes should have simultaneous- 

 ly taken place in the female. Again, natural selection would 

 have led only to monotypic evolution. A comparison of the 

 male organs of some of the allied species of Hawaiian beetles, 

 especially in those cases where geographical isolation appears 

 to be the chief factor of evolution, would be of great interest. 



These lu'ief remarks on very complex subjects are only to 

 show how many important and interesting subjects await the 

 investigation of the naturalist, and all the time such great 

 questions await elucidation there is need for such societies as 

 ours. We may not be able to answer the questions ourselves, 

 l)ut every correct observation is a new stone in the final edifice. 



The labors of Blackburn and Perkins mainly, and of several 

 members here present secondly, have placed the Hawaiian insect 

 fauna on a systematic basis which enables us now to grasp and 

 study the interesting problems connected with its evolution ; 

 to understand more thoroughly the causes which keep our in- 

 sects from increasing in numbers ; the various means which 

 lead to their isolation ; the adaptations that have taken place 

 to enable them to fit their various present habitats and habits 



