Le 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 andlowers 
the death-rate of our cities and towns. Thus, while stables 
and other filthy places are tolerated by 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 by 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, however, 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, why do flies appear sud- 
denly and in such immense numbers, may be answered by 
the statement that they multiply in a geometrical progres- 
sion, and that a single female in suitable seasons and sur- 
rounded by plenty of food may producesuch a number of des- 
cendants ia one year that to éxpress it requires thirteen 
figures. But flies have not their own way in everything as 
