I recently posted some pictures of this ground beetle with abnormal milky-white eyes and asked if anyone knew the cause (click here for post with more pictures)
I also posted a picture with the same request on Twitter and after it had bounced around for a bit got a reply from entomologist Dr. Ross Piper @DrRossPiper who identified the likely cause - a parasitic gordian worm aka nematomorph aka horsehair worm, that grows in its host and can have this effect on its cuticle. Infected hosts tend to wander around in broad daylight and seek water, where the parsitic worm emerges from its host to breed.
He sent me the link to this amazing footage of a tropical example (WARNING:GRUESOME)
Gordian worm emerging from a grasshopper
Really wish I'd captured the beetle and brought it home now.