The sheep headfly, Hydrotaea irritans (Fall.) (Diptera, Muscidae): larval habitat and immature stages

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AbstractNumerous habitats were sampled for larvae of sheep headfly, Hydrotaea irritans (Fall.), in infested areas of Northumberland during the winters 1973–74 and 1974–75. Most of the larvae found came from near the surface of soil beneath pasture and long grass. The mean larval density in these sites was 1·93/m2; the greatest density in a single site was 3·87/m2 which compares well with unpublished estimates of adult fly density. Only two larvae were recovered from cow dung. One larva was found in bracken litter, and none in other types of litter, or in horse dung, peat, moss or rotten wood. Larvae were reared to the mid-third instar from eggs laid in the laboratory. Field-collected larvae fed readily on Musca and Calliphora larvae, and did not appear to diapause in December; their identity was confirmed by rearing them to the adult stage. The egg, second- and third-instar larvae, and puparium are described and figured. Descriptions are given of changes in the mouthparts during growth of the third-instar larva, and of the features by which field-collected larvae can be identified.