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Brachinus alternans? - Brachinus alternans - female

Brachinus alternans? - Brachinus alternans - Female
Dead Lake, Greene County, Alabama, USA
July 22, 2015
Size: 14.5mm
I identified this specimen as Brachinus alternans using (Erwin 1970).

1. Elytra concolourus, epipleura dark. Head & pronotum lighter than elytra.
2. Mentum flat with 2 shallow lateral pits.
3. Metasternum longer than diameter of middle coxa.
4. Elytra blue/green.
5. Elytra uniformly pubescent.
6. Raised medial portion of mentum with several setae (6+), and submentum with many hairs (16+).
7. Metasternum longer than middle coxa
8. Proepipleura & proepisternum pubescent throughout.
9. Elytral costae very pronounced (visible without a scope).

I am not entirely confident in separating Brachinus alternans from Brachinus viridipennis. I looked at over 100 specimens caught in pitfall traps, and the shade of their elytra varied greatly from blue to green, and colors in between. The majority seemed blue.

Any input would be greatly appreciated, thanks!

This specimen was collected by NEON using a pitfall trap containing a 1:1 ratio of water and propylene glycol.

Images of this individual: tag all
Brachinus alternans? - Brachinus alternans - female Brachinus alternans? - Brachinus alternans - female Brachinus alternans? - Brachinus alternans - female

Moved from Bombardier Beetle.

I think you're right
I was on the fence with the ones I caught here, as you probably remember, and they all turned out to be alternans, confirmed by Bob Davidson. Apparently viridipennis looks totally different.

Awesome, that is good to know! I wish there were images of B. viridipennis somewhere, I had read on that there is a specimen in Harvard, but there were no images I could locate on the MCZ. I might still attempt a visit there before I head out of NY.

Thanks for the advice as always Thrasher! I would love to attach some images of the variation in the color of the elytra, can you tell me how you attach images to a post?

No problem
The pictures of the color variation can be added to the Brachinus alternans images page, as separate individuals. You can of course tag these images here and move them to the species page- I think you've got more than enough evidence supporting your determination!

I just found pictures of the type of Brachinus viridipennis just by googling it. It's listed by it's original name- 'Brachinus viridis', which may be why you missed it. Looks totally different, the humeri are extremely sloped.

How did I miss that?
I can't believe I missed those obvious picture under the synonymous name..... The humeri are certainly much different from any of the specimens I identified, a big relief.

Thanks for the lookout Thrasher.

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