248 NATURE STUDY REVIEW [9:8— Nov., 1913 



and the bacteria of the soil will disintegrate the material too 

 rapidly for maggots to develop in it. Thus, these lessons on the 

 fly may not only influence the daily cleanliness of the home, but 

 may effect the saving to garden and field of many millions of dollars 

 worth of soil fertility now annually wasted. 



The outcome of this work should be the steadfast determination 

 of every member of the community that no pile of rotting filth shall 

 be permitted to endanger the health or life of a baby. 



Many cities and towns have already done so, and all must, the 

 sooner the better, pass ordinances and develop plans for removal of 

 all fly-breeding filth at least once a week during warm weather. 

 Here the school children can aid greatly in spreading the knowledge 

 and in developing sentiment in the homes for careful observance of 

 such regulations. Several cities print the fly lessons on leaflets and 

 distribute freely to the children in order to give them something 

 authoritative to carry into their homes. Dr. Jean Dawson's 

 leaflet in Cleveland has probably, more than any other one thing, 

 influenced public sentiment to support the work in that city. 



Ordinary house or typhoid flies, have been reared from maggots 

 found in the snuff of a druggist's counter. This means that as 

 long as there are flies around, they will succeed in finding something 

 in which to lay their eggs. We must, therefore, attack the problem 

 from both sides. We need to work for clean cities, towns, farms, 

 and homes for many other reasons. The flies indicate the lines on 

 which the general cleaning up must be done and constitute the 

 sharp point of the wedge which must start things moving. 



If the rate at which flies multiply were taught clearly in every 

 school, to every boy and girl, the rest would be easy. A pair of 

 flies may produce from 120 to 150 eggs at a laying and may live to 

 lay at least six batches at intervals of eight to ten days. These 

 eggs become adult flies in about ten days and are ready to lay the 

 first batch of eggs when from ten to fourteen days old. If we start 

 out with a pair of flies May ist, how many will we have, if all 

 were to live by August ist ? (allowing 150 eggs at a batch, six layings 

 to a pair, and each pair beginning to lay when ten days old). 

 Have the pupils work this out independently and see how near 

 right the following figures are : 



May I we begin with 2 flies 



June I we have 117,702 flies 



July I we have 6,484,702 flies 



Aug. I we have 5,748,870,600 flies 



