Variation in the proportion of different reproductive stages of female bushflies (Musca vetustissimaWlk. (Diptera, Muscidae)) in bait catches as a cause of error in population estimates

Abstract

Most trapping techniques for estimating populations assume that all individuals are equally trappable. Where potential protein sources are used as baits for muscoid flies, which are known to have a cyclical intake of protein during ovarian development, numbers caught may not be comparable. Accumulated field data on the reproductive stages of samples of the bushfly (Musca vetustissima Wlk.) in a study area near Canberra have been analysed to show that only flies in the last stages of maturing their eggs (reproductive stage IV) are uniformly under-represented (about 22% of expectation) in baited samples.