224 BIOLOGY FOR BEGINNERS 



always the case) then one fly would produce in the different 

 generations of two weeks each as follows. 



1st 200 (half females) 



2nd (100x200) 20,000 ( " " ) 



3d (10,000x200) 2,000,000 



4th 200,000,000 



5th 20,000,000,000 



6th 2,000,000,000,000 



2,020,202,020,200 total in 12 weeks 



or the perfectly unthinkable number of over two million millions 

 in half the breeding season, which would be over 20,000 flies to 

 be killed by each man, woman, or child in the United States - 

 and this the progeny of one adult female which survived the winter. 

 Fly Control. Fortunately there are more efficient ways of de- 

 stroying this dangerous pest. These are briefly tabulated below: 

 government bulletins fully describing all methods may be had for 

 the asking, and general cooperation has much reduced the pest 

 in many cities. The following are the most efficient methods of 

 control : 



1. Horse manure and other filth can be removed, screened, or 



chemically treated to kill the larvae. 



2. Garbage and sewage can be properly covered and removed. 



3. Houses can be screened. 



4. Food, especially in stores, can be protected. 



5. Fly traps and wholesale poisons are helpful. 



The Mosquito. The mosquito is another member of the diptera 

 which demands mention because it, too, transmits serious diseases 

 to man though it acts in a different way from the fly. The germs 

 actually develop a part of their life history within the mosquito's 

 body, while the fly merely carries its dangerous burden, 

 mechanically. 



Mouth Parts. In the mosquito, the labrum, tongue, mandibles, 

 and maxillae are reduced to sharp, lance-like bristles, enclosed 

 within the labium as a sheath, and are adapted for piercing and 

 sucking. In order to dilute the blood, so that they can withdraw 



