ANENT THE INSECT WAR 15 



insect-carried diseases out of the country, if such diseases do not 

 occur here and if there are any known carriers of the disease among 

 our insect population. Yellow fever is an excellent example. We have 

 the yellow fever mosquito and if persons suffering from this disease 

 should enter any part of the country where the mosquito occurs the 

 disease might well become established. Every effort should be made 

 to reduce the numbers of the house-fly, stable-fly, and other pests. On 

 the other hand the introduction of parasites, particularly of imported 

 pests, should be encouraged and people should learn to differentiate 

 at least the more beneficial of their insect friends. 



Morphology of Diptera 



It is not my intention to go into detail concerning the structure 

 or morphology of flies since I have appended a glossary of terms used 

 in this and other works. However, a few remarks on the subject may 

 not l)e amiss. In Williston's manual a simple system of nomenclature 

 is used and I follow the same system. During recent years attempts 

 have been made to homologize the parts of the various orders of insects 

 and as a result many long and unfamiliar terms have been proposed. 

 To my mind the homologies of the parts are much less important to 

 the systematist than a simple, easily followed and long used termin- 

 ology. Nevertheless it is important to know the origin of the various 

 parts, especially so to a zoologist, if he deigns to study that group wliieli 

 comprises three-fourths of the animal kingdom. In each order of in- 

 sects a simple terminology has long been in use and such terms should 

 he employed because the average student can understand them without 

 difficulty. After all, some one has said that "Nature is an open book, 

 and you have but to study nature to understand." Perhaps those are 

 not the exact words, but they will do. 



The determination of genera is based upon structure and it is 

 therefore necessary to be acquainted with these parts. The average 

 student will find no difficulty on this score if he will follow the simple 

 expedient of using the keys and consulting the glossary. In this way 

 the terms used will soon be mastered and the student will find little 

 difficulty in tracing out specimens. 



The student who desires to delve into the anatomy of Dipter;' 

 should obtain a bibliography of the works on this subject, particularly 

 those by Crampton and Snodgrass. ]Many references will be found in 

 Imms' "Recent Advances in Entomology" and "Biological Abstracts" 



It will be found that autliorities differ as to the origin and homol- 

 ogy of different organs. A comparison of the Oomstock-Needham sys- 

 tem as used by Dr. Alexander in this work and that of Comstock will 



