This fly lays its eggs in manure or other refuse, these hatching out,
passing through all their stages and emerging as perfect insects in a
few days. Their uncleanly habits make the house flies most efficient
agents in the carriage of different diseases, especially typhoid fever
and others which attack the digestive tract. Flies are therefore not
merely a nuisance to be deplored, but a positive danger to mankind.
Among other flies are the carrion flies, black flies, the gnats and the
mosquitoes, all troublesome to man, while others attack various plants.