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Genus Metrius

Primitive Bombardier Beetle - Metrius contractus Tenebrionidae? - Metrius contractus Metrius contractus Bombardier Beetle - Metrius contractus Metrius contractus Metrius contractus Metrius contractus sericeus - Metrius contractus Ground beetle - Metrius contractus
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Coleoptera (Beetles)
Suborder Adephaga (Ground and Water Beetles)
Family Carabidae (Ground Beetles)
Subfamily Paussinae
Tribe Metriini
Genus Metrius
Synonyms and other taxonomic changes
Metrius Eschscholtz, 1829
Two species: (1)(2)(3)
Metrius contractus Eschscholtz -- CA to southern BC
Metrius explodens Bousquet and Goulet -- Idaho
9 to 13.5 mm (4)
Black, convex beetles found from California to British Columbia, as well as Idaho.
Both spurs of front tibia apical (as opposed to one being preapical)
Head with one setigerous puncture over each eye.
Hind coxae not contiguous.
Middle coxal cavities disjunct.
Anterior coxal cavities closed.
This genus is known only from western North America. (1)
Secretes defensive chemicals (quinone-based and hot, like bombardier beetles) as a frothy mixture that can either be held at the rear of the body or channeled forwards along special tracts. This is perhaps a primitive state among beetles with similar defensive chemicals. See Eisner et al. (5) for more detail.
Internet References
Tree of Life: Metrius.
Works Cited
1.American Beetles, Volume I: Archostemata, Myxophaga, Adephaga, Polyphaga: Staphyliniformia
Arnett, R.H., Jr., and M. C. Thomas. (eds.). 2000. CRC Press LLC, Boca Raton, FL.
2.Catalogue of the Geadephaga (Coleoptera: Trachypachidae, Rhysodidae, Carabidae including Cicindelini) of America north of Mexico
Y. Bousquet and A. Larochelle. 1993. Memoirs of the Entomological Society of Canada, 125: 1-397.
3.Description of a new species of Metrius from Idaho with comments on the taxonomic status of other taxa of the genus.
Bousquet, Y. and Goulet, H. 1990. The Pan-Pacific Entomologist, 66: 13-18.
4.The ground-beetles (Carabidae, excl. Cicindelinae) of Canada and Alaska, parts 1—6
C.H. Lindroth. 1961. Opuscula Entomologica Supplementa XX, XXIV, XXIX, XXXIII, XXXIV, XXXV.
5.Spray mechanism of the most primitive bombardier beetle (Metrius contractus).
Eisner, T., et al. . 2000. Journal of Experimental Biology 203, 1265-1275.