No worries Andy, I actually wasn't too assertive with my first answer, and meanwhile I had time to look at it properly: there's a work on Russian mutillids, but it's in Russian, still one of the main references on Palearctic mutillids; it takes some time (to me) to wade through it. Mutillid wasps are among my very favourite insects, so please do post photos of them if you get some more (if you manage to make them hold still long enough for a photo that is); sadly, some species are not identifiable from photos (only under a potent microscope), and one's required some practice to understand individual variation. I'm not sure how many species you have around there (St Petersburg), but I'd guess less than 10 (between 5 and 10?), whereas they're in the order of 60 species in Iberia (with some species probably yet to be described), making it a bit complicated. Cheers