Leaf beetle - Trirhabda geminata

Unusual "Lateral" Spots on Head

Usually there's a single spot (or band bulging out) at the middle of the back of the head...not two separate ones on the sides. Maybe this was a recently emerged adult in the process of "developing" spot and color patterning, as you've mentioned in other posts. Still, I haven't seen or read about any occipital spots like this before.

… Aaron Schusteff, 15 January, 2012 - 1:46am

I collected larvae

from Brittle Bush, and this adult was freshly out of the pupa. I can try again this year and keep them longer, document changes.
Still, this one looks funny with the two spots.

… margarethe brummermann, 15 January, 2012 - 11:48am

Even the other one

still just had spots

… John R. Maxwell, 15 January, 2012 - 7:42am

Spots

There are always three spots on the pronotum in Trirhabda.

My remark above referred to the two lateral spots at the hind edge of the head in the image at the top of the page.

In T. geminata there's usually a single, dark, medial, tongue-shaped spot which widens towards the back of the head and is referred to as the "(occipital) plaga" in the literature. The broader base of the plaga is usually obscured by the overlapping anterior edge of the pronotum.

The image at the top of this post shows two spots positioned laterally at the back on the head, whereas the individual in the thumbnail John linked to has a very unusual (for T. geminata) centrally isoloated occipital plaga. (But it also has two vaguely darkened lateral "spotlets" in the groove on the anterior edge of the pronotum...which is unusual as well.)

These occipital plaga anomalies in the AZ posts of T. geminata, together with the unusually small pronotal spots...both characters more in line with T. schwarzii...make me wonder whether something interesting is going on between the two taxa in this region?

… Aaron Schusteff, 19 October, 2013 - 4:12pm

Moved

Moved from Trirhabda.

… margarethe brummermann, 9 January, 2012 - 1:40pm

Moved

Moved from Trirhabda.

… margarethe brummermann, 9 January, 2012 - 1:40pm

Moved

Moved from Leaf Beetles.

… margarethe brummermann, 22 September, 2008 - 6:35pm

looks like Genus Ophraella??

… Jason W., 10 August, 2008 - 10:20pm

pls move to Trithabda page

bitte sehr?

… v belov, 17 September, 2008 - 5:12pm

To me it looks

like Trithabda, maybe geminata. Mature older ones are darker pigmented.

… margarethe brummermann, 3 September, 2008 - 12:49pm

It could be T. geminata or sc

It could be T. geminata or schwarzi. You don't by chance know what plant you found them on? Any other shots, side view or closer up?

… John Randall Watts, 9 September, 2008 - 9:30am

Brittle bush, Encelia farinosa

is the host plant. The beetles are pretty much destroying the 2nd generation of leaves (from after the monsoon rains) of the bushes which will then be bare till the spring rains come. We have larvae right now but I'll try to get an adult beetle side view.

shows an older specimen with more pigmentation

… margarethe brummermann, 17 September, 2008 - 6:19pm