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Phorocera obscura

Phorocera obscura is one of the most common Parasitic Flies in Britain. Few people ever realised they saw it though. It doesn't look like your typical parasitic fly: in stead of a robust, rounded body it has a rather slender body. And the markings are very similar to those of the Common Flesh Fly. No doubt many people do think that's what they observe, when actually seeing this parasitic fly. The larvae live on caterpillars of moths, Geometers mainly, even though sometimes they are found on Noctuids. Phorocera obscura concentrates on species flying about in autumn, winter or spring, such as the Pale Brindled Beauty, the Scarce Umber Moth, the Spring Usher and the Winter Moth. The adult flies are seen from April to mid-June. This species only has one generation a year.