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Home » Guide » Arthropods (Arthropoda) » Hexapods (Hexapoda) » Insects (Insecta) » Beetles (Coleoptera) » Polyphaga » Series Cucujiformia » Longhorn and Leaf Beetles (Chrysomeloidea) » Leaf Beetles (Chrysomelidae) » Skeletonizing Leaf Beetles and Flea Beetles (Galerucinae) » Galerucini » Section Coelomerites » Trirhabda

Genus Trirhabda

Classification · Explanation of Names · Numbers · Size · Identification · Range · Habitat · Season · Food · Life Cycle · Remarks · See Also · Print References · Works Cited

sage brush leaf beetle - Trirhabda pilosa

Groundselbush Beetle - Trirhabda bacharidis

Unidentified beetle? - Trirhabda flavolimbata

Classification

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.

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

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)

Unidentified Trirhabda images sorted by host plant

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.

Contributed by tom murray on 19 October, 2005 - 10:33pm
Additional contributions by Beatriz Moisset, Robin McLeod, Chuck Entz, Mike Quinn, Aaron Schusteff, Ron M., v belov, John Pearson, KenW
Last updated 4 February, 2019 - 4:14pm

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