The face fly, Musca autumnalis De Geer, and aggregation behavior in Holstein cows

Studies of interactions between face flies and Holstein cattle show that the frequency and duration of aggregation episodes can be associated with exposure to face flies and that the numbers of flies on cows during aggregation is inversely correlated with cow nearest-neighbor distance, a relationship that remains relatively consistent within herds. Furthermore, aggregation in herds exposed to face flies neither altered herd grazing time nor grazing patterns, which indicates that aggregation behavior is expressed during nongrazing, idling periods. Initial observations show that cow aggregation in small herds does not compromise animal thermoregulation.