Possibly a female (by mandible size) - please see comment below
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I found a rather badly-written but detailed account on the web. It said (amongst other things) that although there is sexual dimorphism - the males have bigger mandibles - they reproduce asexually, both "sexes" laying an egg. Can anyone confirm this?
Also - think there is more than one UK species, so latin name may not be correct!
I have never heard of males laying eggs! Asexual species (common in plants but rather rare in animals) tend to lack males altogether.
University of Edinburgh and Biodiversity Observatory (OU)
The method I use to tell the sexes apart is that the males have noticeably broader front tarsi than the females, but I can't see the tarsi in your photo. I hadn't heard of the mandible size being a clue to the sex.
I was also not aware of Carabus beetles reproducing asexually, and my web searching has been inconclusive - a few papers do seem to hint at asexual reproduction being an adaption of some Carabus species in the northern parts of their range, but I haven't yet found anything that gives a clear explanation. As Jonathan says, it won't be males laying eggs, but instead female-only populations that can lay fertile eggs without mating. Will see what else I can find out on this.
Entomologist and biological recorder
for the comments above.
Lat/Lng: 54.6, -1.4
OS grid ref: NZ4028