TNTHODUCTIOX. IX 



Diptera may always l)e recognized by the presence of but 

 one pair of wings; the second pair of other insects is really 

 represented by a small organ on each side back of the true 

 wings, consisting of a short, slender stem with a knob-like ter- 

 mination, called the halteres or poisers. Their function is 

 not known ; that they have some function seems certain, as 

 they are always in vibration during flight. Not all flies are 

 winged; in some degraded forms, both among the lowest and 

 highest groups of the order, they may be entirely wanting, as 

 also the halteres. Sometimes the males will have wings and 

 the females be wingless. But the numl)er of wingless foi'ms 

 is very small. 



In the adult state the habits of flies are very various. Some, 

 but not a very large proportion, are predaceous upon other 

 insects, sucking their juices. Some are very annoying to man 

 and other warm-blooded animals, sucking their blood ; of these 

 may be mentioned the mosquitoes, black-flies, horse-flies, sta- 

 ble and horn flies, the tsetze fly, etc., as well as all the pupipara, 

 which are parasitic upon birds and mammals. By far the 

 largest number of di])tera, however, feed upon vegetable sub- 

 stances, either fresh or decaying, the pollen and honey of 

 flowers, etc. Some feed upon ordure and decaying material 

 of whatever nature it may be. 



In the larval stages, the habits are yet more diverse. Brief 

 references to the larval hal)its will be found in the following 

 pages. Suffice here to say that the larger pai't are vegetable 

 feeders, but not a few live upon decomi)Osing animal matter, 

 or in the living bodies of other insects, snails, re])tiles, birds, 

 mammals, etc. While some members of the order may be 

 very annoying or prejudicial to man's economy, the order, 

 upon the whole, is a beneflcial one, whether in tlie larval or 

 mature stages, whether as parasites u]M)n other, and injurious 

 organism, or as scavengers. 



In the following ])ages I endeavor to give such deflnit-ions 

 and descri])tions of tlie mature insect as will ( nable tlie stu- 



