1 1- \ 259 



l-'i, ed typhoid haeilli from 6 ity-three days after 



they h;i<l been infected. 



in tact, .1 mvat amount of evidence h.-i- accumulated p that 



transmit not only tliebaeilli of typhoid fever, hut many other 



ria, and often in enormOUfl nuinl.ci ! example, Esten and 



n in their study of the sources of bacteria in milk, collected arid 



examined lli, s from st alMes. pi^-pens, houses and ot her pla< <<, and found 



an average of 1,222,570 bacteria per fly; the majority of the^e lieini^ 



objectionable kinds of bacteria. 



Musca Domestica. A single female of the common house fly lays 

 in all some six hundred eggs. In midsummer, in Washington, D. C., 

 the eggs hatch in about eight hours; the larval period is from four to 

 lays and the pupal period five days, making the cycle about ten 

 days in length. In cooler parts of the season the cycle requires more 

 time and in warm climates it may be as short as eight days. The 

 number of generations in Washington is probably not more than 

 nine (Howard). 



Control. One of the best baits for flies in houses is formalin, which 

 is poisonous to flies but harmless to man. This is prepared by diluting 

 formaldehyde with five or six times as much water and exposing it in 

 shallow dishes, the addition of a little sugar or milk making the solution 

 more attractive to flies, which drink it and quickly die. Pyrethrum is 

 effective against flies, but only when it is pure and has been kept from 

 exposure to the air. Pyrethrum, the chief basis of all the common 

 insect powders, is applied by being puffed through a bellows or by being 

 burned. The powder may be moistened and shaped into cones which 

 when lighted at the top burn slowly and give off fumes that are suffocat- 

 ing to insects. 



Dr. Howard estimates that more than ten million dollars are spent 

 every year in screening houses in the United States. Another enormous 

 sum is spent for fly papers and fly traps. The efficient way to deal with 

 the fly problem, however, is to prevent the insects from breeding. Ex- 

 crementitious substances should be enclosed in such a way as to prevent 

 the access of flies, or should be treated in a way to kill the larvae therein; 

 one of the simplest methods of treating stable manure being to spread 

 it out to dry, since the maggots cannot develop without moisture. 



For detailed information on everything of importance relating to 

 the house fly, and particularly on the mitigation of the fly-nuisance by 

 concerted action in communities, Dr. Howard's adrrirable book on the 

 house fly should be consulted. 



