False Metallic Wood-boring Beetle - Trixagus carinicollis

Moved

… Richard Migneault, 23 January, 2013 - 4:07pm

Trixagus carinicollis (Schaeffer)

I think this is actually Trixagus carinicollis (Schaeffer). Although its difficult to see in the ventral photo, I'm pretty sure that I can see the divided eyes that characterize Trixagus Kugelman. Aulonothroscus Horn has its eyes entire, and A. constrictor (Say) is normally larger (2.5-3.3 mm) than this specimen. The loose fringe on the margins of the elytra distinguishes a male of T. carinicollis and distinguishes it from T. chevrolati (Bonvouloir).

Richard: if you can take a photo from the front that shows the eyes we can confirm this identification.

… Christopher Majka, 23 January, 2013 - 3:58pm

Front & eyes photo added

… Richard Migneault, 23 January, 2013 - 4:52pm

aulono

From what I can see here I disagree. The characters of the eyes is not diagnostic; several aulonothroscus also have divided eyes. The only way to separate them externally is the tarsal grooves om the metasternum.
I'm away from home now and don't have my auonothroscus references but I will verify this when I get home. I do have my trixagus revision handy and Yensen mentions the eye carinae in some aulonothroscus.

I'm limited to viewing on a blackberry now but from what I can see, I stand by my original diagnosis of aulonothroscus.

… Blaine Mathison, 23 January, 2013 - 4:17pm

Trixagus carinicollis (Schaeffer)

Hi Blaine, I don't know about other species of Aulonothroscus, but A. constrictor (Say), the only species found in Atlantic Canada, has entire, undivided eyes. This specimen, in contrast, has deeply divided eyes, characteristic of Trixagus. It's not that easy to see in the face-on photo posted here since the head is well retracted into the pronotum, but Richard has examined the specimen and assures me this is so. Also, being very familiar with both of these species (I have examined hundreds of specimens) I can say that A. constrictor is always castaneous in colouration and not the piceous colour of Trixagus. Furthermore, in my experience A. constrictor (at least in this region) is almost always 2.8+ mm in length whereas Trixagus spp. are almost always smaller, and this specimen is 2.4 mm. There's hardly ever any overlap in size. There's no question but that this is Trixagus and from the elytral fringe and sinuate base of the pronotum it's clear that it is T. carinicollis.

… Christopher Majka, 24 January, 2013 - 8:36am

yes...

I have recently reviewed my notes and constrictor does have entire eyes. I have looked at the underside image here several times and I am starting to think I've been mislead by shadows under the middle legs, mis-interpreting them as the outline of the tarsal grooves.

I am content with this being Trixagus. Thanks for the follow-up.

… Blaine Mathison, 25 January, 2013 - 2:51pm

Moved

Moved from False Metallic Wood-boring Beetles.

… Blaine Mathison, 14 December, 2012 - 7:02pm