The stable fly is one of the most serious pests of confined livestock. In many areas it is becoming a more serious pest of pastured cattle as well, associated with hay waste residues from the large, round hay bales fed in pastures. Adult stable flies of both sexes require frequent blood meals (often daily) and feed preferentially on the lower body and legs of cattle. Stable flies have long bayonet-type mouthparts called a proboscis, which they use to tear through the skin causing blood to pool at the skin surface. These bites can be quite painful.
Stable flies have very poor survival at temperatures above 86 ºF (30 ºC), thus limiting their activity during hotter summer periods in geographic locations where mid-summer mean maximum temperatures substantially exceed this threshold. Stable flies are considered to be more abundant during high rainfall years, presumably due to the widespread increase in available immature habitat. Recent studies in California have shown that stable fly biting intensity during late spring and early summer was related to March rainfall, with greater rainfall in March resulting in greater abundance of stable flies during the peak abundance period in late spring and early summer (late April-June).