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Scaeva pyrastri

In the genus Scaeva there are two similar species in Britain. One can tell them apart easily though, at least in most cases. Scaeva pyrastri has its comma markings on the body yellow, Scaeva pyrastri has white comma-shaped markings. There is a certain overlap in colouring, though. Another help is the fact that usually the commas in Scaeva selenicita are slightly larger. However, every now and then a more difficult beast presents itself. These can be identified by studying the genitals under the microscope. Both species have a dark brownish to black thorax, covered in hairs, but unmarked. The adult flies eat nectar and pollen. The green, flat worm-shaped larvae eat aphids, but they hunt by night only. The two species are rather big flies, reaching a length of 12 to 15 millimeters.