Thanks for your comment, Scott. I thought at first that this was an Ichneumon or Braconid but in Borror, De Long and Triplehorn on p.663 it states that the entire Ichneumonoidea (except one small, rare family) is characterized by the absense of a costal cell, among other things. This specimen does have a costal cell. On p.667 they say that chalcids can be recognized by the characteristic wing venation shown in their fig. 571 B, on p.645. This specimen does conform to that but with a greatly enlarged stigma. It was this stigma which I had hoped would enable someone to determine family. I added a photo which may show the costal cell more clearly.This tiny wasp is actually bigger than the majority of chalcids. (p.666)

This is a Torymidae. The stigma is sort-of diagnostic for this family of Chalicidoids. They also often have long, exposed ovipositors.

Thanks for the family, Andy. I looked on the Torymidae page and where the wing is clearly shown the enlarged stigma is visible and often can be seen even when the wings are folded. Sometimes not, but it may well be there.