What's That Bug? does not endorse extermination

Subject:  Beetle eating banana slug Southeast Alaska
Geographic location of the bug:  Juneau, AK
Date: 10/22/2017
Time: 02:03 PM EDT
Hi there! I see these beetles wandering the ground and on and under rotten logs all over Southeast Alaska and the rainforests of the Pacific Northwest (WA, OR, British Columbia) and I have not been able to ID them! They have these wonderful purpleish abdomens and are maybe an inch long or less. This one was found with a baby banana slug in its jaws! What is it?
How you want your letter signed:  Thanks! -Mike J

Snail Eating Ground Beetle with immature Banana Slug

Dear Mike,
Your image is gorgeous.  We have several images on our site of Snail Hunters or Snail Eating Ground Beetles in the genus
Scaphinotus, but your image is the only one showing its preferred prey.  According to BugGuide:  “55 spp. in 9 subgenera total, all in our area.”  Several species are known from Alaska, including Scaphinotus angusticollis which is pictured on BugGuide and Scaphinotus marginatus which is also pictured on BugGuide.  Both species look very similar to your individual and we are not confident enough to provide an exact species identification for you.  According to Bugs of the Month:  “Scaphinotus angusticollis is large (satisfyingly so) and black, with a beauteous purple or greenish sheen in sunlight. The thorax is peculiarly shaped, turned up at the outer edges (a bit like a satellite dish), the legs are quite long and slender and the head is distinctly narrow and elongate. Truly the Afghan hound of the carabid world. The narrow head is an adaptation to eating snails from the shell. Now there are shelled snails in forests around these parts, but with forest clearing and the introduction of non-native pests, shelled snails are less frequent and slugs abound.”

Wow thank you for the thorough reply! They really are quite beautiful, and now I know that the beetles I see eating snails and on the ground are snail eating ground beetles 🙂 You are right, those two species are nearly identical, I guess if I was on the spotI would tell someone it was Angusticolus.

Thanks again!
Stay Curious

Mike Justa
Wildlife Naturalist
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What's That Bug? does not endorse extermination
Location: Juneau, Alaska

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