Lindroth, in the Carabids of Canada and Alaska, states that Laemostenus complanatus was first recorded in North America by Crotch in 1873. It still amazes me that these relatively big beetles (about 15mm long) have been stowing away on ships probably since the time of the voyage of the Beagle. Likely they were in NA and elsewhere, having been moved from their native north Africa, long before Crotch’s report.
No doubt a cozy berth in that ship ballast. I have seen them in Australia, Hawaii, New Zealand and out on the Juan Fernandez Islands (where for a moment I thought I had something wonderful and undescribed :\ ). They were probably dumped together with Alexander Selkirk (the character that Robinson Crusoe is based on) in 1704. After all, rats cats and goats where there already.
Now I have a resident population of them in this little impromptu terrarium of dirt and leaves next to my house. This abandoned sprinkler unit (I ripped up the rest to xeriscape the lawn) is in a sea of concrete, but the L. complanatus seem, well, snug as bug. Doesn’t get much more synanthropic than this. I never find them out in the more natural areas away from houses, so I don’t guess they do much harm. They hang with Amara, Calathus, Trechus and assorted Harpalines that live in my lawn. Given the body count near webs, they must be a pretty good snack for my ample Black widow population.