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Genus Trirhabda

Beetle - Trirhabda I think - what sp.? - Trirhabda adela Mating beetles - Trirhabda bacharidis - male - female Trirhabda Chryso 5 - Trirhabda convergens More Trirhabda on Solidago - Trirhabda Beetle - Trirhabda blue beetle larvae on solidago - Trirhabda
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Coleoptera (Beetles)
Suborder Polyphaga (Water, Rove, Scarab, Long-horned, Leaf and Snout Beetles)
No Taxon (Series Cucujiformia)
Superfamily Chrysomeloidea (Long-horned and Leaf Beetles)
Family Chrysomelidae (Leaf Beetles)
Subfamily Galerucinae (Skeletonizing Leaf Beetles and Flea Beetles)
Tribe Galerucini
No Taxon (Section Coelomerites)
Genus Trirhabda
Explanation of Names
Trirhabda LeConte 1865
Greek tri "three" + rhabdos "rod". May refer to the three pronotal spots (like rods in cross-section), or to the three linear stripes on the elytra of some species.
Numbers
26 spp. in our area(1), ~30 spp. total(2)
Size
Adult 5-12 mm; larva 5-10 mm
Identification
Third antennal segment shorter than the fourth (a key characteristic);
Elytral color varies with species (yellow, green, bluish-purple, blackish), sometimes with a metallic luster. Many species have longitudinal elytral vittae [= stripes];
Pronotum yellow with 3 round or oblong dark spots (1 medial spot and 2 dorsolateral spots);
Head yellow with dark occipital [rear top of head] spot;
Larvae caterpillar-like, but, like other beetles, only have the six thoracic legs and (unlike caterpillars and sawfly larvae) no prolegs.
Host plant info often critical for species identification.
Key in Wilcox (1965)(3)
Range
NA (so. Canada to Central America); introduced elsewhere (e.g., Australia)
Habitat
Weedy fields, brushy areas
Season
Adults May-Aug; larvae Apr-Jun
Food
Host plants are in the families Asteraceae and Hydrophyllaceae. Larvae and adults usually feed on leaves and flowers of a single plant species or genus: one group of species feeds on goldenrod (Solidago); another group on wormwood (Artemisia); another on Yerba Santa (Eriodictyon); etc.
Life Cycle
One generation per year; overwinter as eggs; pupate in the soil.
Remarks
The following text applies to an undetermined species (shown here) that occurs in coastal southern California:
"Abundant from spring to summer on Isocoma venetus. The adults and larvae are found together feeding on foliage of this plant. Larvae are a dark metallic green, and adults are in life bright yellow with dark metallic green stripes."
See Also
In Galerucella, Ophraella, and Xanthogaleruca, antennomere 3 is longer than antennomere 4 (shorter in Trirhabda)
Print References
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 (Full text)
Blake D.H. (1951) New species of chrysomelid beetles of the genera Trirhabda and Disonycha. Journal of the Washington Academy of Sciences, 41:324-328. (Full text)
Hogue S.M. (1970) Biosystematics of the genus Trirhabda LeConte of America north of Mexico (Chrysomelidae: Coleoptera). Ph.D. dissertation, University of Idaho, 212 pp.(4) The most complete reference to date.
Works Cited
1.Phylogeny and host plant association in the leaf beetle genus Trirhabda LeConte (Coleoptera: Chrysomelidae)
Swigoňová Z., Kjer K.M. 2004. Mol. Phylogenet. Evol. 32: 358-374.
2.American Beetles, Volume II: Polyphaga: Scarabaeoidea through Curculionoidea
Arnett, R.H., Jr., M. C. Thomas, P. E. Skelley and J. H. Frank. (eds.). 2002. CRC Press LLC, Boca Raton, FL.
3.A Synopsis of the North American Galerucinae (Coleoptera: Chrysomelidae)
John A. Wilcox. 1965. New York State Museum and Science Service.
4.Biosystematics of the genus Trirhabda LeConte of America north of Mexico (Chrysomelidae: Coleoptera)
Steve Munroe Hogue. 1970. Ph.D. dissertation, University of Idaho, 212 pp.