The development, population dynamics, and predation rates on the eggs and first instars of the house fly,Musca domesticaL., of the manure-inhabiting mite,Macrocheles muscaedomesticae(Scopoli), were simulated in a FORTRAN77 model. Effects of mite crowding on fecundity were determined experimentally, and long-term population dynamics experiments were conducted under simulated field conditions for model development; other data used in development of the model were obtained from the literature. Features of the model include: nonlinear development, longevity, and attack rate routines for variable temperatures; mite fecundity as a function of temperature, mite crowding levels, physiological age, and prey quantity and type; attack rates as a function of mite crowding and prey quantity and type; mite survival as a function of crowding and habitat size and quality; and a house fly submodel that tracks deposition, aging, and destruction of fly immatures. Mite populations are updated by the model every 4 h. Comparison of predicted mite populations with actual populations from validation experiments were in close agreement, and improvements in agreement were achieved by empirical adjustments of mite survival as a function of changes in habitat quality over time.