Update 19th April 2008: This specimen was not correctly identified, as it is actually T. simrothi subsp. festae. However, the images on AntWeb are still incorrectly labelled as T. ambiguum, so perhaps I shouldn't feel too bad!
I've been fairly quiet recently because I've been busy trying to identify ant specimens, rather than writing about them. However, this one deserves a special mention.
Back in September I attended a BWARS workshop on two pairs of closely related species. None of the species are especially common in the UK and one from each pair is more common than the other.
We were able to find two specimens of Stenamma westwoodii, a near endemic in the UK (it's also found in Belgium), to compare with S. debile. However, between all of us and the collection at Oxford University Museum we could not produce a single Tapinoma ambiguum to compare with T. erraticum - or at least if we did no one told me! I was rather disappointed, as I had seen T. erraticum many times from Europe, but had not once seen T. ambiguum.
A few weeks ago I agreed to look at some specimens collected by David M. King. One of the specimens from Turkey is a very obvious T. ambiguum, so I have now seen it! The attached photomontage [removed] shows the cloacal aperture, low petiole, four dorsally visible tergites on the gaster and shallow clypeal notch that characterises the species.
This appears to be the only reliably identified photograph of this species online, as the images named T. ambiguum on AntWeb are clearly T. erraticum. The depth of the clypeal notch on the AntWeb specimens is equal to their width, whereas in T. ambiguum the depth should be less than the width.