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Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Suborder: Adephaga
Family: Amphizoidae
Genus: Amphizoa
LeConte, 1853

6, see text

Amphizoa is a genus of beetles, placed in its own family, Amphizoidae.[1] The vernacular name "trout-stream beetle" comes from the original finding of A. insolens and A. lecontei in high mountain streams, although other species occur at lower elevation. They are notable as a possible intermediate stage between terrestrial and aquatic beetles; while living in the water, they are not good swimmers and physically resemble ground beetles more than other types of water beetle.

Ranging in length from 11 to 16 mm, they are generally a dull black, with a squarish head and a pronotum significantly narrower than the elytra.

The larvae also live underwater, but breathe through the eighth abdominal segment and must therefore stay close to the surface. They cling to rocks or floating debris. Both adults and larvae are predators, but will also scavenge dead insects.

When disturbed, adults exude a yellowish fluid from the anus, with an odor described as that of cantaloupe or decaying wood, probably as a defense mechanism against hungry frogs and toads.

The genus comprises six species, three from western North America and three from China.[2]

Species include:[3]


  1. ^ Amphizoa LeConte 1853. Illinois Natural History Survey.
  2. ^ a b Roughley, R. E., et al. (1998). Amphizoidae: Description of Amphizoa smetanoi sp.n. and supplementary description of A. davidi Lucas. In: Jach, M. A. and L. Ji (Eds.) Water Beetles of China Vol. II 123-29.
  3. ^ Amphizoa. Integrated Taxonomic Information System (ITIS)

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