Trirhabda flavolimbata? - Trirhabda flavolimbata

Belated observation

I've been studying Trirhabda with some concerted effort lately, and recently realized that the aedeagus was conveniently visible in the second image of this series. I've posted a more detailed crop of it, as a 4th image in the series.

The most viable alternative to T. flavolimbata here would be, T. labrata...which is very similar looking, sympatric in some areas, and shares the same host plant! It has larger pronotal spots than T. flavolimbata, and much sparser pubescence on the elytra, which is why I went with T. flavolimbata here.

However, size of pronotal spots and pubescence can be variable...and without viewing large series of specimens, it's sometimes hard to feel comfortable determining an ID based on such characters. But, now it turns out the shape of the aedeagus cements the ID here as T. flavolimbata. See the remarks posted with 4th image for details.

… Aaron Schusteff, 10 January, 2012 - 12:28am

good detective work -

thanks!

… Boris Büche, 2 August, 2007 - 9:21am

Thank you Boris...

...the detective work was facilitated by good leads provided by you and others :-).

For future reference, here's where I am now re: identifying this beetle. Evans & Hogue's "Field Guide to California Beetles"(1) states there are 16 Trirhabda species known from California (it doesn't list them all, but briefly discusses 5). I was able to obtain what I presume to be those 16 species names by digging towards the bottom of this list.

Comments on BugGuide by Hartmut Wisch and you led me to focus on host plants. Evans & Hogue give host plant info for 5 of the 16 species. And host plant info for 8 more appear in the interesting cladogram within an article referenced by Hartmut (see page 3 of this newsletter). So we have host plant info for 13 of the 16 species, the 3 "unknowns" being: T. attenuata, T. labrata, and T. manisi. Modulo these 3 unknowns, only T. flavolimbata uses Baccahris pilularis as a host plant, which my field observations convince me is the case for the beetle in question. Moreover, photos of the type specimen of T. flavolimbata seem to compare well with my specimens. (That link indirectly from you:-)

So the question is: What about those other 3 species? I couldn't find host plant info for them on the web. I did find a photo set of the type specimen of T. labrata, and a reference stating it is recorded from nearby (Santa Cruz Co.). There's a reference to a work dating from 1931 in the article Hartmut found:

Blake, D.H. 1931. Revision of the species of beetles of the genus Trirhabda north of Mexico. Proc. U.S. Nat. Mus. 79(2):1-36.

If I get a chance to look it up at a nearby research library that might help. I'll keep trying :-)

[PostScript I, added on 6/5/09: I did eventually get to study Blake's paper and more, everything points unequivocally to T. flavolimbata ID.]

[PostScript II, added on 8/9/10: I just found Blake's 1931 is now accessible online via the Biodiversity Heritage Library: Read online here, or download as PDF here]

… Aaron Schusteff, 6 August, 2007 - 1:11am

great work

yeah nice yellow legs too (=flavolimbata if I´m right). Beetles from California are really hard for there is little info on California beetles and many beetles. Think you´ve set a nice reference here to compare future pictures with.

… Rob Westerduijn, 3 August, 2007 - 1:02pm

Aha, I get your point...

...translating from latin: "Flavo" = Yellow and "limbata"= Limbed. I hadn't noticed the connection. I like that!

Yes, a modest little monograph with complete coverage of California Coleoptera and detailed keys and descriptions would be a very nice present for someone out there to confer upon us :-) A truly monumental task I presume! However, we are fortunate to be graced with two relatively recent books by Evans and Hogue(1)(2) which are well-written and full of interesting and helpful info.

I'm glad you liked the photos, thanks for your comments.

… Aaron Schusteff, 4 August, 2007 - 5:44am

Oops...I was a bit too sloppy with my latin!

Found a reference on the web stating that the latin word "limbata" is derived from "limbatus", which means "bordered". So perhaps the epithet in Trirhabda flavolimbata refers to the yellow edging of the elytra (rather than yellow limbs). Actually, I think yellow limbs and elytra edges may appear on many different species of Trirhabda.

I guess trying to match an organism and a name by a conjectured interpretation of the epithet can be risky, though fun if it works :-) Would be nice to have that "dream monograph" to settle such questions.

… Aaron Schusteff, 4 August, 2007 - 7:15pm

I was a bit too sloppy with my latin

I figured about the border some later too. Suprizing how many meanings the word limb has by the way (eg. leg, arm, border, leafblade). It should probably have been flavopenne or somethink like that for yellow legs. Anyway sure it doesn´t exclude other species, but it helps some. Especially tells you think again if it doesn´t figure!
For California Chrysomelids you can also use this list: http://www.sbnature.org/collections/invert/entom/chrysomelids.pdf

… Rob Westerduijn, 6 August, 2007 - 12:54pm

Yep...

etymology is fascinating...kinda of a provides a vague phylogeny of ideas :-) I agree that translating latin names often provides a helpful check for a tentative identification. But even the sanctity of descriptive scientific names can fall prey to mischievous pranksters. An example from botany: Thimbleberry, an attractive shrub in the Rose family in the western US. It has flowers that are among the largest in its genus. Yet its binomial is Rubus parviflorus (parvi = small !).

PS: Thanks for the pointer to the California Chrysomelid list.

… Aaron Schusteff, 7 August, 2007 - 2:48am

horrors of taxonomy

in Peru etymology is sometimes the only lead I´ve got....That is, a list with names.....and with my poor understanding of latin....argg

… Rob Westerduijn, 8 August, 2007 - 4:00pm

Entomological Etymology

I ran into this and thought it might be helpful :-)

… Aaron Schusteff, 10 August, 2007 - 11:00pm