ENTOMOLOGY HOWARD 361 



of the human species still has many gaps. How much more, there- 

 fore, with its pitifully small number of workers, is there to be 

 learned about insect physiology ! Fundamentally radically dif- 

 ferent from the vertebrate structurally, how importantly must their 

 physiology differ! And upon their physiology as greatly as upon 

 their structure must their behavior depend. In the main, we know 

 what they do only as it affects our interests. We must know every- 

 thing that they do and why and how they do it. Here phj^siology 

 is basic. To understand their reactions, to be able intelligently 

 to explain their tropisms, we must know how they direct their 

 movements, how they communicate, how they hear, how they see, 

 how they digest their food, and the scores of other things upon 

 which a complete knowledge of their physiology would throw 

 light. 



I think it is quite certain that this is the largest as it is sm'ely 

 the most important of the comparatively unexplored fields in en- 

 tomology. What information there is exists in scattered papers 

 in many languages, and many of the investigations in so-called 

 physiology are really little more than studies of internal anatomy 

 in which the histology of organs is considered from a more or less 

 comparative point of view. Enlightening work has been done on 

 the structure of the sense organs, notably that of Mclndoo on the 

 olfactory organs of insects of several different orders. But phys- 

 iology in general from its experimental and chemical aspects has 

 hardly been touched. Such studies as have been made are not as- 

 sembled so that we can readily know where we stand. Although 

 the fii*St part of Packard's text book is entitled "Morphology and 

 Physiology," and covers over 500 pages, it is almost wholly anatomi- 

 cal, and it is 26 years old. 



One of the greatest and most important fields in human phys- 

 iology and in that of domestic animals, and one which is being 

 most intensively worked, is that of nutrition. AVliat do we loiow 

 about the food elements necessary to insects? And just how is 

 this food utilized ? Here is a field Avhich is crying for investigation 

 by the best trained men, using the most advanced methods and 

 able, in fact, to invent new methods — men of the genius of Krogh, 

 of Denmark, for example. 



As already indicated, upon our knowledge of the physiology of 

 insects must depend our understanding of their tropisms, and upon 

 a clear understanding of these tropisms will depend many of our 

 future methods of warfare. 



When we speak of tropisms and behavior we are touching upon 

 what stands for psychology with insects. Kecently, in the AVorld 

 War, we have had a striking example of the enormous handicap to 



