Temporal and spatial trends in adult nuisance fly populations at Australian cattle feedlots

A comprehensive trapping program to determine the species composition, seasonality and distribution of adult nuisance fly populations at a southern Queensland feedlot was conducted from 2001 to 2003. Short-term information on nuisance fly populations was also collected from two feedlots located in other climatic regions. Twenty-five species of Diptera were identified. The more commonly trapped species were the house fly, Musca domestica L. (Muscidae) (38%), the hairy maggot blowfly, Chrysomya rufifacies (Macquart) (Calliphoridae) (27%) and the bush fly, Musca vetustissima Walker (Muscidae) (15%). Seasonal effects were the major determinant of fly populations. All commonly trapped fly species had low abundance during the coldest winter months, July and August. Musca domestica had one annual, broad peak in abundance starting in spring and extending over about 8 or 9 months. Musca vetustissima had a major abundance peak in October/November and a smaller peak around April. Stomoxys calcitrans (L.) (stable fly) (Muscidae) showed two annual peaks in abundance, with the major peak in May. Chrysomya spp. were most abundant during spring, summer and autumn, whereas the highest numbers of Calliphora augur (F.) (blue-bodied blowfly) (Calliphoridae) were trapped in winter. The sites within the feedlot with the highest catches of M. domestica were the feed mill, cattle pens and the hospital area and of S. calcitrans the manure piles, silage pits and the feed mill. The lowest catches of M. domestica and S. calcitrans were obtained in the traps situated a few kilometres outside the feedlot. In contrast, M. vetustissima and blowfly catches were higher in outside traps and traps near the manure piles than any other feedlot site. There was a correlation between the animals' number of fly avoidance movements and M. domestica catches and between the number of leg stomps and stable fly catches, respectively