House fly populations in Pennsylvania increase rapidly in June, peak in September, and decline with cold weather in early October. From seven to nine generations occur during the fly season. Broken eggs, failure to control leaky waterers, and an occational dead bird in the manure storage add to the problem. High-rise houses normally are cleaned only once or twice a year. While house flies are only a minor direct annoyance to livestock, their potential for transmission of diseases and causing a public nuisance are of major concern.
Stable flies are vicious biters commonly associated with dairy and equine operations.
Male and female stable flies feed several times each day, ingesting one or two drops of blood at each meal. When not feeding, adult flies rest in the shade on posts, trees, and buildings. Breeding takes place in wet straw, spilled feeds, silage, and decaying vegetation. The stable fly's life cycle is longer than that of the house fly, requiring about 3 weeks to complete under optimal conditions. Eggs hatch in 1 to 3 days, and the maggots feed for 11 to 30 days before reaching maturity, depending on the weather.