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Green beetle - Trirhabda flavolimbata

Green beetle - Trirhabda flavolimbata
Point Reyes, Point Reyes National Seashore, Marin County, California, USA
April 10, 2013
Size: ~3/8"
A quite cooperative subject. Green somewhat lighter than shows in photo, with a metallic sheen.

Moved from Trirhabda.

Hi Bob :-)
Long time no see...hope all's well with you.

Just ran into your post here. It looked like T. flavolimbata to me right off the bat, and there are a few posts of that species from Pt Reyes:

Although I think it's unlikely there any other Trirhabda species in the Pt Reyes area, I walked your photo through the key in Hogue(1) to check, and indeed it keyed to T. flavolimbata and is in excellent agreement with the description there.

While it's on grass here, I suspect it fell or wandered off a nearby Baccharis pilularis shrub, which is their primary host...though I have seen them feeding on Baccharis douglasii:

I've also seen them cavorting on Symphyotrichum chilense (=Aster chilensis), though they didn't appear to be feeding. As you know, all three of those asteraceous species are present at Pt. Reyes, with coyote brush being the most common (almost ubiquitous) and B. douglasii the least common (infrequent in wetland adjacent habitat).

Point Reyes' siting
We discovered the Abbott's Lagoon this passed weekend and came across so many of these. Is there a layman's name for these? Oddly, my 12 y/o noticed that most of the beetles on the trail were moving right to left (North to South) across the trail. Is there any significance to that observation?

Thanks for the report, Jason
I know of no common name for this beetle. Though even if there is one out there, I usually prefer "scientific names" (= latin binomials). They're not so bad once you get used to them, and are less ambiguous...and often more fun :-)

The genus name here Trirhabda is pronounced "try-rob-da" and means "three rods"...presumably referring to the three conspicuous dark round spots on the pronotum that are distinctive of all species in the genus. The specific epithet flavolimbata means "yellow-bordered", referring to the thin yellow edge along the border of the elytra (although other species are also yellow-bordered).

Not sure what the significance of the north to south movement may have been...but among other things, it may be an indication that your 12 y/o is a budding naturalist :-).

Hi Aaron,
Good to hear from you.

Here is a guy on a Baccharis pilularis that was crawling with them. (Another time and place, but still Point Reyes NS.) Looks like it may be a gravid female, actually.

Martha says hello.

Aaron Schusteff worked hard to curate this section
hope he gives you a name

Moved from ID Request.

Great pic

Artistic and good for ID as well.

Green beetle (=Trirhabda confusa?)
Thanks, Ross. It looks like a spitting image of Trihbabda confusa, Photo#113350, to my inexperienced eye.

T. confusa is a close "look-alike" T. flavolimbata. But its host plant is rubber rabbitbush (Ericameria (=Chrysothamnus) nauseosus), which wouldn't occur anywhere in Pt Reyes. There is a population of both E. nauseosus and T. confusa in the summit area of Mt Hamilton, high to the east of San Jose...the closest occurrence I can think of to Pt Reyes:

The literature mentions six similar-looking species in California - some of which share the same host.

Trirhabda group…
See reference here.

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