16 NORTH AMERICAN DIPTERA 



show certain differences while others disaoree in the terminology as 

 applied to the veins in other families of Diptera as well as in other 

 orders of Insects. It must be pointed out that the Comstoek-Needham 

 terminology of wing venation is very widely used, probably by more 

 students of Diptera than any other system, and if American students 

 desire to study exotic flies they must familiarize themselves with this 

 system as well as the system used by many Europeans. Explanations 

 of these systems will be found in the glossary. 



Classification of Diptera 



The classification of any .grou]) of animals is a complex problem 

 having its basis in the morphology, histology, embryology and general 

 biology of the phylum, and without a knowledge of these "ologies" 

 no satisfactory classification can be obtained. In addition we must also 

 turn our attention to paleontology, although it must be confessed that 

 very little is known concerning the Diptera of the past ages. In the 

 present work we deal almost entirely with morphology of the adult 

 flies, not from any desire to ignore the other phases of study, nor from 

 any lack of interest in them, but because our space is so limited and 

 each field is so vast that a lifetime of study would leave any field 

 almost untouched. The truth is that we know practically nothing 

 about the biology of flies although we may say, in a general way, that 

 we are acquainted with their mass biology and that we can usually 

 place a species biologically by associating it with some related form. 



The taxonomist, however, is forced to deal with adult structures, 

 to classify thf creatures by characters he may select and to leave to 

 some one else the pleasure of working out the biology of the insects 

 studied. If you are at heart a taxonomist and are informed that you 

 know nothing of ])iology unless you study life histories, do not be dis 

 couraged. Instead, feel rather strongly inclined to turn a deaf ear to 

 your adviser, taking solace in the fact that even though you may spend 

 all your available time at the systematic study of the adult insects, and 

 gleaning what you may from the writings of others on biology and life 

 history studies, you will never be able to fully master the field you 

 have chosen. There are so many flies that no one can ever truly profess 

 to know them all and their very numbers preclude a thorough survey 

 of the orcTer tending to a complete classification. 



It is well, and necessary, to warn against too great specialization, 

 and at the same time it is realized that many students with limited time 

 are unable to study more than one or two families. The great trouble 

 with the intensive specialist is that he loses his sense of proportion and 

 relatively minor details are liable to assume the greatest importance in 



