AdultPhilonthus flavolimbatusErichson collected near College Station, TX, in 2-day-old bovine manure pats were used to establish a laboratory colony. In subsequent laboratory tests, 5 adult beetles placed on manure reduced the number of adult horn flies,Haematobia irritans(L.), that emerged from 100 eggs to 6 (a 91% reduction when corrected for control mortality) and 10 beetles almost completely (+99%) eliminated production of adults from 100 eggs. The reduction was primarily the result of predation on the eggs. In simulated field tests, similar ratio of one beetle to 10 horn fly eggs gave only a 72% reduction.