---

There were a number of these flies on leaves, flitting around after a rain.

I don't know what family to assign. To me it is reminiscent of house fly and other Muscidae, but then there are several families that have this overall appearance. What are the keys here?

Thanks in advance for any ID help!

Taken yesterday afternoon, 13 July 2006, West Virginia USA, open area but not far from a woodland. Size was smaller than a house fly, but not miniscule.

---

Your judgement in spot on. This could be a slender muscid or a robust anthomyiid. Someone familiar with the N. American fauna could probably tell you more, but I don't recall seing exactly this kind of pattern on European species.

These families where split apart mainly in the basis of structure of male genitalia. Many genera are easily classified as one or the other on external characters, but there is overlap in most single characters, for example all muscids have a truncated first anal vein on the wing, but a few anthomyiid genera share this characters.

---

Try the online key http://www.nku.edu/~biosci/CoursesNDegree/ForensicFlyKey/families.htm to Calyptrate Families as a first step.See Weblinks Medical, Forensic etc. The key is from Kentucky- blue grass so I'm told. Nice colour :p:p. Here it's green.A kind of wet :(:(green. Robert