It was two months ago that I posted this image claiming it to be Tapinoma ambiguum. I was wrong - but that is nothing new!
Shortly after posting it I took the specimen to Cedric Collingwood, who glanced at it under a microscope and said 'Ah, it's festae!' Since then I've been planning to update this blog with a proper correction, but I wanted to be sure that I know why it is this species.
Why did it take so long? Basically, there is almost no information available on Tapinoma simrothi subsp. festae. It was described by Emery (1925), which I haven't been able to get hold of. I can find nothing else relating to it, aside from a mention in unchecked taxa in Agosti & Collingwood (1987). This entry has a question mark next to it, says that it's expected for the Balkan peninsula and the species is not featured in the key that followed.
Since I haven't encountered anything that clarifies the situation in the last two months, and forgot to ask Collingwood about it last time we spoke, I'm basing my acceptance of this identification on the fact that it is much larger than T. erraticum. T. ambiguum should be the same size as T. erraticum.
As far as I can make out, the size distiguishes T. simrothi from T. ambiguum and T. erraticum. T. simrothi subsp. festae is then distinguished by the shallow anteromedian clypeal notch, which is deeper than wide in T. simrothi. This makes me wonder whether it is the Tapinoma sp. mentioned in Collingwood & Agosti (1996), even though the scape index of this specimen is shorter at 97.
I expect that at some point T. simrothi subsp. festae will be raised to species status, as it seems to differ from T. simrothi no less than T. ambiguum does from T. erraticum.