Comparison of core sampling and pupal traps for monitoring immature stable flies and house flies (Diptera: Muscidae) in beef feedlot pens.

Core samples and cylindrical pupal traps were used to monitor immature stages of the stable fly, Stomoxys calcitrans (L.), and house fly, Musca domestica L., from 5 sample areas in beef feedlot pens: the feed apron-soil interface, the back fence, the side (pen dividing) fence, the mound, and the general lot. One feedlot was sampled during 1986, two feedlots were sampled in 1987, and three samples were taken at random from each sample area on each sample date. Core samples showed that both populations were highest from the feed apron sample area. Pupal traps tended to show the same result but differences between sample areas were not significant for immature stable flies. Both sampling methods generally indicated similar population trends of the 2 fly species over the season; correlation coefficients between the 2 sampling methods were generally significant but few correlations were strong and large divergences between population trends were present. Only approximately 69% of the total number of pupal traps placed were recovered; the loss of traps could have contributed to differences between the 2 sampling methods. Core sampling would be preferred if lower variance of samples is important; if collecting pupae of known age is important, then pupal traps may be useful if they are protected from trampling by cattle.