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Weevil

Idiostethus subcalvus

Description:

<2mm long weevil on an anemone flower.

Habitat:

Stillhouse Falls Hollow, Tennessee.

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22 Comments

KarenL
KarenL 11 years ago

It does! Thanks for all your help with this too Jack!

oxyjack
oxyjack 11 years ago

Cool! That would explain why we couldnt find a match!

KarenL
KarenL 11 years ago

Bugguide has advised this is their first spotting on this species!

KarenL
KarenL 12 years ago

ID'd by bugguide.net

Mark Ridgway
Mark Ridgway 12 years ago

...but then I would have also fallen for Trichapion nigrum....

Mark Ridgway
Mark Ridgway 12 years ago

Wow karen I just had a look at Ischnopterapion virens and I would have fallen for that so easily. It's a good thing to have an oxyjack around. Looking forward to finding out what this one is.

oxyjack
oxyjack 12 years ago

You're welcome, wish I could have gotten you closer to the correct ID. At least we know the subfamily, that's something. =)

KarenL
KarenL 12 years ago

:) It certainly seems to be your specialist subject!
Thanks again for all your help Jack!

oxyjack
oxyjack 12 years ago

I'm sure it isn't the species you originally had as the ID, the punctation on the elytra was wrong. And it lacked the white hair-like scales bestween the grooves. I just checked all of the Baridine tribes and genera on bugguide, and they didn't have your weevil, but maybe one of their weevil people (2 of the world's leading experts chime in there from time to time) will recognize it. Unfortunately, your picture is blurry in places where it would be very nice to see some detail. There's a suggestion of texture on the pronotum, but I can't clearly see what that texture is. That can make a difference when determining a weevil species. (I studied weevils in grad school, can you tell?) =)

KarenL
KarenL 12 years ago

I'm amazed that anyone can identify anything this small!
I've put in an ID request to bugguide too so maybe they can help!

oxyjack
oxyjack 12 years ago

It looks like your guess wasn't far off, it's in the same subfamily!

oxyjack
oxyjack 12 years ago

I take it all back... my initial ID, that is. Now that I've looked at it more closely, I'm convinced that it's not a Brentid, but a true weevil (Curculionidae). The body shape is very similar to the pear-shaped weevils, but now I'm convinced it actually belongs in the subfamily Baridinae. I'm used to seeing large (over 2 cm) specimens from that group, but I checked, and sure enough, there are tiny ones (2-3 mm) found on flowers. I'm looking through the different tribes now trying to find a likely candidate. I'll update my ID when I find something.

KarenL
KarenL 12 years ago

Oh well, back to the drawing board!
Thanks for your help Jack!

oxyjack
oxyjack 12 years ago

I just took a closer look at Ischnopterapion virens, and I'm pretty sure it's not the same weevil. Yours has distinctly elbowed anntennae, with a pronounced scape (the long segment closest to the head). The other weevil has many similarly sized antennal segments. Sorry. We'll have to keep looking.

oxyjack
oxyjack 12 years ago

Yes, those guys can be really tiny, there is a common hollyhock weevil on the west coast that's around 7mm with including snout, and the snout is half the body length easily. These weevils are sexually dimorphic, the females have much longer snouts than the males. Their ovipositors are the same length as their snout, they chew out a tunnel in plant stems until they can't reach any deeper, then turn around and lay their eggs in the tunnel.

If you recall green scales then it very well could be Ischnopterapion virens, but I'm hesitant to positively ID something that small unless I can look at it under a microscope and then compare it to identified specimens. I can see that it will be very hard to get accurate IDs for the smaller arthropods on Project Noah. The plants, mammals, birds and such are much easier, as are the moths and butterflies, and the bigger beetles.

KarenL
KarenL 12 years ago

It looked green in some of the other photos that I deleted because they weren't crisp enough to post. It was really too tiny to see anything with the naked eye! I put 3 mm but it was probably no more than 2 mm long.

oxyjack
oxyjack 12 years ago

The white hairs look right. Did yours also have small iridescent green scales? It's sometimes hard to pinpoint to ID with photos, it's so hard to see the necessary details.

KarenL
KarenL 12 years ago

Thanks Gerardo!
Thanks for the comment & the ID correction Jack! I've checked out the link - could this be a green weevil Ischnopterapion virens? http://bugguide.net/node/view/593781

oxyjack
oxyjack 12 years ago

This is an Apionine Brentid weevil. Great picture!

Gerardo Aizpuru
Gerardo Aizpuru 12 years ago

Wow!

KarenL
KarenL 12 years ago

Thanks Argy! Same camera but I've invested in a macro converter!

Mark Ridgway
Mark Ridgway 12 years ago

Lovely shot at 3mm Karen. Did you get a new camera recently :)?

KarenL
Spotted by
KarenL

Tennessee, USA

Spotted on Mar 14, 2012
Submitted on Mar 15, 2012

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