Dear Lars,
you're fully right!
I confused the tip of the abdomen with another tooth in postero-lateral view.
Well, it seems that only
Chrysis coerulans is already known from various localities in Canada in this species group (Bohart & Kimsey 1982).
At this time, I cannot go any further with ID too...
The problem with the names
nitidula/coerulans and all related synonymies is still unsolved.
Kimsey & Bohart (1991) considered only one valid species (
C. nitidula).
However, reading the desciption of Form A, Form B and Form C of
C. coerulans (given in Bohart & Kimsey 1982) it's clear that in this group there are more species, perfectly matching the European species in the
C. ignita group (they show the same habitus, punctuation, etc., only the colour is different).
Also Linsenmaier (1994) observed that more species are found in this group and he named them with numbers because he could not examine types deposited in American museums.
Most of these European taxa were considered as variations, forms or subspecies until the second half of the XX Century, but now they are all accepted as valid species (also thanks to molecular analyses). I suppose that the same situation can be observed in North America within the species of the
C. nitidula group.
Cheers
Paolo