A comparison of the Diptera caught in Manitoba traps with those caught from cattle and other parts of the field ecosystem in northern England

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Abstract
Manitoba traps were used in a pasture field in northern England between June and October in 1980 and 1981.Samples of Diptera were also collected from cattle, cow dung, the field surface and from flowers in the hedges. A comparison of these samples, using multivariate similarity coefficients, showed that the Manitoba trap and cattle samples were most similar. There were 12 weeks in the two years during which both Manitoba trap and cattle samples were obtained, and the accumulated catches for this period were compared. They consisted mainly of cattle-visiting species, the proportion being greatest in the Manitoba trap samples (97%). Non-cattle-visiting species in the cattle sample (25%) consisted mainly of dung flies and species associated with the field surface. It is suggested that these were taken accidentally in proportion to their abundance around the cattle. There were some differences in the proportions of various species between the samples from cattle and the Manitoba trap, and the sex ratio of the three most abundant species was significantly higher in the traps. An experiment in which a large electrocuting grid was used to intercept flies travelling towards artificial bait as used in Manitoba traps, showed that the proportion of the two most abundant species differed significantly from a sample obtained from a nearby Manitoba trap. No such difference was observed in the sex ratios of these species.