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Genus Trirhabda

Leaf beetle - Trirhabda geminata Trirhabda adela? - Trirhabda Trirhabda? - Trirhabda Black Catepillar - Trirhabda Larva - Trirhabda sage brush leaf beetle - Trirhabda pilosa Groundselbush Beetle - Trirhabda bacharidis Unidentified beetle? - Trirhabda flavolimbata
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Coleoptera (Beetles)
Suborder Polyphaga
No Taxon (Series Cucujiformia)
Superfamily Chrysomeloidea (Longhorn 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.
26 spp. in our area(1), ~30 spp. total(2)
Adult 5-12 mm; larva 5-10 mm
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)
NA (so. Canada to Central America); introduced elsewhere (e.g., Australia)
Weedy fields, brushy areas
Adults May-Aug; larvae Apr-Jun
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.
Gravid female Trirhabda will often have remarkably distended abdomens...see comment here.
See Also
In Galerucella, Ophraella, and Xanthogaleruca, antennomere 3 is longer than or equal in length to 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.