The diets of Natterer's bat Myotis nattereri and the common long-eared bat Plecotus auritus were investigated at a nursery colony of each species by analysis of droppings collected monthly from May to September. Respectively, 68% and 42% of the diets comprised items presumed to have been gleaned from foliage or other surfaces: diurnal insects, insects which rarely fly, and non-flying arthropods. Such surfaces included the ground: centipedes were eaten by both bats, and the muscid, Scatophaga stercoraria, usually associated with cattle dung, was a common prey. Indeed, the prevalence of cattle-farming around both of the bat roosts almost certainly contributed indirectly, in the form of S. stercoraria, to a significant part of the Diptera consumed. The chief food of M. nattereri was the larger Diptera, but Trichoptera, Hymenoptera and Arachnida were also important. Lepidoptera, Coleoptera and Hemiptera were minor prey, with Dermaptera and Chilopoda taken occasionally. Diptera, closely followed by Lepidoptera, together accounted for nearly two-thirds of the diet of P. auritus. Also taken, in descending order of importance, were Trichoptera, Arachnida, Chilopoda, Coleoptera, Dermaptera, Hymenoptera and Hemiptera. Plecotus auritus, but not M. nattereri, was evidently able to take a few small insects such as aphids and lesser nematoceran Diptera.