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The stable fly (Stomoxys calcitrans) and horn fly (Haematobia irritans) are mainly parasites of cattle that spend the early phase of their life cycle in decaying vegetation, manure and soil, as members of a wide range of other harmful and beneficial arthropods. Predators of the family Macrochelidae are considered beneficial mites that have been considered promising biological control agents of fly eggs and larvae and of other harmful organisms. The objectives of this study were: a) to compare the predation and oviposition rates of three Macrocheles species, M. embersoni, M. muscaedomesticae and M. robustulus, on six prey species: S. calcitrans, Musca domestica , H. irritans, Bradysia matogrossensis, Rhizoglyphus echinopus and the free living nematode Rhabditella axei; b) to evaluate the life cycle of the best performing predator (M. embersoni) on the most suitable prey species at 30 ± 2°C, 95 ± 5% RH and in the dark. The three macrochelid species consumed all evaluated prey species, but M. embersoni had higher predation and daily oviposition rates on larvae of S. calcitrans (23.8 larvae consumed and laid about 4.0 eggs, respectively) than other species. Total immature development of M. embersoni was completed in at most about 1.3 days on eggs of S. calcitrans and M. domestica and 1.5 days on R. axei. Macrocheles embersoni produced most eggs (0.28-0.34 female/female/day; r m : 0.28-0.34) on those same prey. The results of this study suggest that M. embersoni is a promising biological control agent of S. calcitrans and M. domestica.

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Larvae of Sciaridae flies (Diptera) cause considerable damage to the mushroom Agaricus blazei (Murrill) ss. Heinemann in Brazil. Brazilian growers have had considerable difficulties in controlling this pest. The objective of this work was to test the effect of the predatory Laelapidae mite Stratiolaelaps scimitus (Womersley) as a control agent of Bradysia matogrossensis (Lane) in cultures of A. blazei. The work corresponded to an evaluation of the efficiency of that predator when released in boxes containing each about 15 L of commercial mushroom compost naturally infested with the pest. The results showed a significant effect of that predator on the population of B. matogrossensis. The release of either 665 or 1330 S. scimitus per box significantly reduced the pest population to levels that, according to grower's experience, apparently could not cause considerable damage. The positive results obtained warrant the conduction of complementary studies to determine the lowest rates of the predator that could still produce acceptable levels of control.