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Wolf Spider with False Bombardier Beetle - Chlaenius cumatilis

Wolf Spider with False Bombardier Beetle - Chlaenius cumatilis
Anza-Borrego Desert State Park, San Diego County, California, USA
March 15, 2007
Size: BL~15 mm
We saw this large wolf spider under a rock straddling a False Bombardier Beetle (Chlaenius probably cumatilis). The beetle averages about 12-14.5 body length, and the spider is larger. This was creekside in Borrego Palm Canyon. Is it possible to get to genus?

Moved from Vivid Metallic Ground Beetles.

Please note that this beetle is most likely C. cumatillis based on the evidence presented and the positive ID of this beetle found at the same time of year, in the same habitat and geographic location. However, this photo obviously does not show enough detail to be identified conclusively. I am retaining this image because of the interesting data presented regarding the frequency of predation by local spider species.

Moved from ID Request.

OK, well I've gone ahead and taken Andy & Mandy's advice and frassed the close-up image of the spider as it was very blurry and probably not worth keeping. I've decided to move this image to the Chalaenius page for now. It really isn't a great picture and the beetle probably can't be definitively identified to species, but as we don't currently have any confirmed images for C. cumatilis in the guide, I thought it might be worth saving if only to preserve the commentary regarding this species. If anyone objects and still feels the image should be frassed, I am OK with that too. :-)

Lynn, you mentioned that you see these beetles quite frequently, I don't suppose you have some other pics you could submit?

Chlaenius sp
I'll be happy to post our "best" photo, but it's not super sharp. A photograher is at great disadvantage with these beetles. They live creekside under fairly good-sized rocks, not ones you pick up but ones you roll up. My husband must hold up the rock while I try to get down and focus in a semi-dark area. Meanwhile, the moment a beetle sees light it dashes off or scurries deeper and out of sight under the rock.

I'll post my reasons for thinking it is very possibly to probably C. cumatilis, but this is not a definitive identification.

PHOTO TIP - beetle under rock
Hi Lynn,
Chose a rock to lift where the sun is to your front and lift the rock toward the sun, so the rock shadow covers the ground that's exposed. If you're able to lift the rock very slowly, there's a chance the beetle might not figure out the change right away, or not feel threatened. Then use flash for your picture since it's still in the shade/shadow. Another thing you can do is take a "studio" with you, a plastic container you can fill with dirt same as where you found the beetle. Drop the beetle in there and hopefully it'll eventually stop in a spot that isn't right next to the plastic walls for a natural photo. I'll typically carry a couple of TV dinner type plastic trays in my backpack for these type of situations.

Beetle under rock
Thanks for the photo tips. Definitely a good idea to always tip the rock toward the sun. Of course, we may tip lots of rocks to find one with beetles, but it we make it a habit, we'll be prepared!

But these beetles are really skitterish--and I can see why. Just in the few times we've seen them, one is being straddled by a wolf spider, and three of them were wrapped up in silk by a Kukulcania spider,#314045.

makes sense
Be great if we can recruit Lynn for some additional/ better beetle pictures :) especially if we can get nice shots of sp. confirmed.

suggesting Frass
I think these pics should be moved to Frass. IDs given probably as much as we can, and both subjects are out of focus. Unless there's other data value I'm not recognizing. Lynn, you have lots of great guideworthy pics, but this time my humble opinion is for Frassing them.

I agree
I can say for a fact that a correct genus and species can't be determined for the spider...only guesses can come from the images. And if placed with the rest of the unidentifiable wolf spiders, it is likely to just sit there collecting dust. Probably best to frass it.

Spider is possibly an Arctosa sp.
The environment and carapace shape/color make me think Arctosa. But I don't think there is any way to be sure of that without an epigyne photo. I'd like to hear others' guesses though, too.

Thanks you!
Thanks for your comments, Mandy. I appreciate your inpute. I just have no knowledge of wolf spiders at all, except for the eyes!

Chalaenius cumatilis would be a good guess indeed

Chalaenius cumatilis
Thanks for the possible confirmation of this species. It seems the most likely to us after revieWing the literature, but other lookalikes do occur in our area. We see these beetles fairly often under creekside rocks in March. They are an metallic blue-black and quite handsome. And also quite vulnerable to spider predation. We found one other spider, Kukulcania, Filistatidae, with three dead silk-wrapped spiders under one rock, which I posted.

Thank you again, v. belov, for all your identifications and mentoring this past year! We are very grateful. May your New Year be healthy and happy! It is guaranteed to be busy as long as you are an editor for BugGuide!

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