148 THE COMMON HOUSE-FLY. 



ever made at all, it should be remembered that flies have an 

 infancy as maggots, and the loathsome life they then lead 

 as scavengers cleanses and purifies the August air and lowers 

 the death-rate of our cities and towns. Thus, while stables 

 and other filthy places are tolerated bj^ city and town 

 authorities, the young of the house-flies, and of flesh- and 

 blow-flies, with their thousand allies, are doing something 

 toward purifying the pestilential air, averting the summer 

 brood of cholera, dysentery, diphtheria, typhus and typhoid 

 fever, which descend like harpies upon the devoted towns and 

 cities. It may be regarded as an axiom that where flies 

 most abound there filth, death-dealing and baneful, is most 

 abundant, and where filth-diseases such as just mentioned 

 do most congregate. 



"When the fly leaves its pupal case, it pushes away the 

 front end of it, which opens like a lid, by means of the dis- 

 tention of the membraneous front of the head, which may be 

 seen pushing out and in as the fly walks rapidly about. 

 When free from its prison the fly runs nervously about, as 

 laboring under a good deal of mental excitement and quite 

 dazed b^- the new world of light and life about it, for as a 

 maggot it was blind, deaf, and dumb. Now its wings are 

 soft, small, baggy and half their final size. The fluid that 

 fills them, soon, how^ever, dries up, the skin of the fly attains 

 the colors of maturity, and it flies off with a buzz suggestive 

 of contentment and light-heartedness born of its mercurial 

 temperament. Fig. 125, plate X, shows the fly in all its 

 beauty". 



"When we consider that each female may deposit as 

 many as one thousand eggs, and that in the course of one 

 summer we may have from seven to nine generations of flies, 

 it should not astonish us that these winged tormenters ap- 

 pear as by magic. The question, w^hy do flies appear sud- 

 denly and in such immense numbers, may be answered by 

 the statement that they multipU^ in a geometrical progres- 

 sion, and that a single female in suitable seasons and sur- 

 rounded by plenty of food may produce such a number of des- 

 cendants in one year that to express it requires thirteen 

 figures. But flies have not their own way in everything as 



