i9i3" I 9 I 4-] The Common House Fly. 127 



enemies — a veritable wolf in sheep's clothing (italics in 

 original). There is no virtue in the house fly; there is no 

 reason why it should continue to exist, and its death-knell 

 is beiug sounded wherever communities care for the health 

 of the individual." " Our descendants of another century 

 will stand in amazement at our blind toleration of such a 

 menace to life and happiness." 



In order to make folks wage a more unceasing war, it 

 has been proposed to rename our household fly the ' typhoid 

 fly,' ' filth fly,' ' manure fly,' &c. Notwithstanding every 

 attempt to prevent their multiplication, it would seem an 

 impossible task. For example, take the following estimation 

 of their rate of reproduction. Say that on 



15th April one fly which has survived the winter lays 

 its batch of 120 eggs. 



1st May 120 adult flies issue, of which say 60 are 

 females. 



10th May 60 female flies lay 120 eggs each. 



28th May 7200 adult flies issue, of which 3600 are females. 



8th June 3600 flies lay 120 eggs each. 



20th June 432,000 adult flies arrive; and so on, until by 



10th September 5,598,720,000,000 adult flies have been 

 given birth to ; and this is, of course, far below the 

 actuality, as each fly lays at least four batches 

 of eggs. 



Happily, however, the enemies — of eggs, larvas, pupse, and 

 flies — are most numerous, and hence but a fraction of the 

 flies comes to maturity. 



In large towns now the substitution of motor - cars for 

 horses has done much to diminish the number of flies ; the 

 breeding-places — the horse-manure heaps — have to a great 

 extent gone, and benefit to the community has resulted. Why 

 is it that in the clean houses of the better classes so few flies 

 are seen ? Merely because of greater cleanliness and thrift. 

 Amongst the untidy poor the houses are not kept clean, 

 remains of food are allowed to lie about, and so the visits 

 of God's scavengers are invited, but unfortunately they bring 

 other evils in their train. Cleanliness, personal and domestic, 

 will therefore afford the means to withstand diseases liable to 

 be brought in this way. 



VOL VII. 1 



