HODGE] THE HOUSE-FLY— A PRACTICAL LESSON 249 



This last figure would mean about 148,875 bushels of flies. 

 Any pupil who is fond of figures may continue the breeding through 

 August and September. One who has done this in World's Work, 

 May, 191 2, gives us as the theoretical increase of a pair of flies in a 

 season: 1,096,181,249,310,720,000,000,000,000 flies. 



Very few flies live through the winter, in at least the larger part 

 of the country, and if everyone realized how many might come 

 from a single fertile fly not one would live to lay her first batch of 

 eggs in the spring. They emerge from winter quarters desperately 

 hungry, and with modern out-door traps set at this time over every 

 garbage can and swill barrel, practical extermination would be 

 complete by the first of June at latest. 



This is not the place for details or information. Within the past 

 two years plenty of out-door fly traps have been designed and they 

 are on the market, and in many places the pupils are making traps 

 after their own designs in manual training departments. Box traps 

 for stable windows catch flies literally by the bushel, and with no 

 trouble and trifling extense, make it possible to completely rid 

 dairies and farm yards by halting the breeders before they can 

 begin to lay. This is effective prevention, and here is the fallacy of 

 those who would limit the work of prevention to cleaning up the 

 filth in which flies breed. Which is easier and better to kill a 

 thousand maggots in a cart load of manure or let the fly walk into a 

 trap, before she begins to lay, and have her around for three months 

 busy carrying filth to food while she is producing the eggs ? 



The final lesson which is well fitted for special emphasis in high 

 school classes in biology, relates to need of perfect civic cooperation. 

 The ignorant or careless household can breed flies enough to vitiate 

 the best efforts of the rest of the community. There must be no 

 ignorant or careless people in such vital matters. After having 

 each member of the class actually work out a plan which shall 

 render all fly feeding or breeding impossible about his own home, 

 go a step further and ask each one to sketch a plan which shall be 

 good enough to enlist every family in the community in this work. 

 Discuss, compare and revise plans until one is agreed upon as good 

 enough to submit to the community, then get it printed in full in 

 the local paper. Many towns and cities have made and tried such 

 plans and these are readily available in the literature. The one 

 feature to be avoided is the offering of prizes or prices for the great- 

 est number of flies killed during any season in which they may be 



