In 1967 and 1968, populations of house flies, Musca Domestica L.; little house flies, Fannia canicularis (L.); black garbage flies, Ophyra leucostoma (Wiedemann), and predaceous manure-inhabiting mites (Parasitidae, Macrochelidae, and Uropodidae) at 3 poultry (caged laying hens) farms having a fly-control program were compared with 3 similar farms with no fly-control measures. Excellent fly control was demonstrated with a program based on early-season manure removal and adult fly control by insecticide-bait stations and 5 or 6 selective applications of insecticide to the inside upper parts of the poultry houses and the interior and exterior surfaces of the attached feed- and egg-storage buildings. Little house flies were controlled more easily than house flies. In the presence of a high population of black garbage flies at 1 farm in 1967, house flies and little house flies were rare. Populations of mites were variable, and no deterimental effects of the insecticide treatments were detected. The order of abundance was Urpodidae > Macrochelidae > Parasitidae. Parasitids appeared earliest in the season followed by macrochelids and uropodids, in that order. Toward the end of the fly season, parasitids disappeared first followed later by macrochelid and then uropodid population declines. A fly-activity index based on fecal spotting of white paper cards provided useful comparisons of farms, and development of that simple sampling tool is recommended.