DIPTERA. 193 



The pomace or fruit flies, or vinegar flies, as they are 

 so often called, feed on decaying fruit or other vegetation 

 which is over-ripe or decaying. A basket of pears may be 

 attractive to these flies, not only as furnishing a meal, 

 but also as a good place to lay their eggs. Their larvae 

 are often seen in poorly-sealed cans of fruit, in pickle 

 jars that have been left open, or in brine barrels. Later 

 -their pupae may be seen around the sides of the containing 

 vessel just above the liquid. They often do damage to 

 grapes on the vines. 



About one-half of the dipterous families live in the 

 water until ready to become adults, feeding upon vege- 

 table matter probably and are supposed to do some good 

 as scavengers. Of the remaining families, some pass the 

 immature stages in the water, some on the land, while 

 the remainder do not depend upon water at all for their 

 development. 



The most notorious of all the aquatic families is the 

 mosquito family. Like all other dipters, the mosquitoes, 

 some of them, have mouth parts adapted for lapping, 

 while others have the piercing and sucking beak. Only 

 the latter sort are important from the human point of 

 view; and of the piercing and sucking sort only three 

 genera, so far as present knowledge goes, are of importance 

 to the human family, because of the relation they have 

 been found to sustain to the spread of certain diseases. 

 These three genera are Culex, Stegomyia, and Anopheles. 

 To Culex belong the mosquitoes that keep up their shrill 

 buz-z-z-z around our heads, stopping only to "take a 

 bite." The mosquitoes of the genus Culex are the car- 

 riers of the disease known as filariasis. Some species 

 of Culex, and the mosquitoes belonging to the genus 

 Stegomyia, spread the yellow fever, The Anopheles 



13 



