412 MINNESOTA STATE HORTICULTURAL SOCIETY. 
about one quarteras thick. The shellis very dense. The eggsthus 
laid hatch twenty-four hours after being laid—in confinement they . 
required from five to ten hours more,and the maggots hatched in 
confinement were smaller than those reared from eggs deposited in 
warm manure. For several days the worms living in this dry man- 
ure did not grow, sensibly. For lack of direct warmth, but more es- 
pecially the want of sufficient moisture and, consequently, of avail- 
able semi-liquid food, seemed to cause them to become dwarfed. It 
is evident that heat and moisture are required for the normal devel- 
opment of the fly, as they are for nearly all insects. 
The maggots molt twice, consequently there are three stages of 
development, and they become sensibly larger at each stage. After 
feeding six or seven days the larva is nearly full grown; its body is 
long and slender, somewhat conical ,jthe head and mouth parts being 
rudimentary; the end of the body is truncated, and bears two short 
tubercles, or spiracles, which contain circular breathing holes with 
sinuous openings, the edges of which are armed with fine projec- 
_tions, forming arude sieve for the exclusion of dust and dirt. When 
about to transform into the pupa state, the body contracts into a bar- 
rel-shaped form, turns brown and hard, forming a case,within which 
the larva transforms into that of the pupa. Our house-fly having asa 
maggot lived a life of squalor,immersed in its revolting food, ap- 
pears after a short pupa-sleep of from five to seven days, as a winged 
being, with legs and wings where before there were no traces, and 
is animated by new instincts and mental traits. 
If in its winged condition it is one of the most disagreeable 
features of dog-days, and people wonder why flies were ever made 
at all, it should be remembered that flies have an infancy as mag- 
gots, 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 tolera- 
ted by city and town authorities, the young of the house-flies and 
the flesh and blow-flies, with their thousand allies, are doing some- 
thing towards 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 filth diseases 
such as just mentioned most do congregate. 
When the fly leaves its pupa-case, it pushes away the front end of 
the case, which opens like a lid, by means of the distention of the 
membranous front of the head, which may be seen pushing out and 
in as the fly walks rapidly about. When free of its prison, the fly runs 
nervously about, as if 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 ma- 
turity, and it soon flies off with a buzz suggestive of contentment 
and light-heartedness born of its mercurial temperament. 
When we consider that each female fly may deposit as many as 
one thousand eggs, and that in the course of one summer we may 
