14 NORTH AMERICAN DIPTERA 



Beneficial Flies 



No group of insects, except, perhaps, the Hymenoptera, are so 

 important to mankind as are the flies. In these two groups are man's 

 best friends among the insects. It woukl be useless to argue about the 

 relative merits of the two orders because we know so little about them 

 that no one is in a position to make any authoritative statement. It is 

 sufficient to say that flies play an extremely important part in the 

 pollination of flowers, but they undoubtedly occupy second position 

 to the bees. It is in the field of predaceous and parasitic members thai 

 these two groups render the greatest service to mankind. If the world 

 should suddenly find itself without flies and bees it would quickly revert 

 to a sphere lacking animal and plant life, so important are these insects 

 in maintaining the "balance of nature". 



I believe that the majority of flies, in relation to the number of 

 known species, are either predaceous or parasitic on other insects. Such 

 large families as the Asilida, Empidee and Dolichopida are all pre- 

 daceous in the adult and probably in the larval stage, while the Bomby- 

 liidi^, Nemestrinidse, Conopidaj and Tachinid^e are insect parasites. 

 Other families or groups can be added to the list and we might also 

 include forms which are predaceous in the larval stage. More about the 

 habits of flies will be found in the following pages. 



Flies are also beneficial as scavengers and examples of their effec- 

 tiveness may be found everywhere. They dispose of carcasses, decaying 

 vegetation and waste animal products and in this way do much to keep 

 the air pure and wholesome. 



Anent the Insect War 



I am aware that there has been some sensational propaganda about 

 "the war against insects" and I cannot forego a few remarks. Insects 

 are our best friends and we owe a great deal to them. They are also 

 our worst enemies but this fact should not be proclaimed from the 

 housetops without at the same time crying much louder of the benefits 

 they give us — flowers, fruits, vegetable, clothes, food, pure air, beauty. 

 The stressing of the danger of the "insect menace" may do entomology 

 a great deal of harm and I think it has already done some. It has 

 taught people to dislike all insects and the fact that the "menace" 

 has not developed perceptably has resulted in some loss of faith in 

 entomologists. 



The Diptera contain some of our worst enemies. The public should 

 be made aware of this and steps taken to eliminate the pests in so far 

 as possible. Every effort must be made to keep people suft'ering from 



