Phylum Arthropoda
Class Insecta
Order Coleoptera
Family Psephenidae
Common Name Water Penny
Distinguishing Characteristics
  • Elytra covers most of the body
  • Serrated to pectinated antennae
  • Posterior pronotal margins and anterior elytral and scutellar margins often crenulate (margin with low rounded teeth)
  • Elytra may not always fit together and is often with tubercles in lines or networks
  • Anterior coxae with exposed trochantin
  • Abdomen with 5-7 sternites (2)
Additional Pictures
Psephenidae contains fifteen known species found commonly worldwide. Some taxa such as Psephenus are more commonly found in the United States (3).

Larvae are commonly found in riparian waters, while adult beetles are mainly terrestrial. Mature adults do return to streams in order to reproduce and are sensitive to pollutants found in aquatic systems (4).

Life History:
Psephenidae go through a semivoltine life cycle (takes two years from egg to nymph to adult). The larvae construct pupal chambers in soft, moist soils in or along a stream bank. These air filled chambers are where the final pupation occurs (2).

Two more recent studies have examined relationships within the Byrrhoidae and Elateriformia families and found Psephenidae to be a sister family with Cynoglossidae. The Psephenidae branch has Eubriinae as a basal group followed by a trichotomy for the other subfamilies (3,5,8).

Physiological Ecology:
  • Larvae are commonly found in riparian waters, where their flattened body aids in forming suction to which cling onto slick rock surfaces (4).
  • Adult Psephenidae display a “play” behavior in order to find and copulate with a willing partner. This behavior occurs only on rock surfaces where stream water is being splashed (6).

  • Feeding Ecology:
    Larvae are primarily scrapers. Some of these food items may include, but are not limited to periphyton and detritus (1,7).

    Food Web Roles:
    Adults as well as larvae are common food sources for many fish species such as trout and bass (7).
    QuickTime Movies


    Additional Links



    (1) Cummins, K., & Merritt, R. W. (1996). An introduction to the aquatic insects of north america. (3 ed., pp. 11-112,399-410,440). Kendall Hunt.

    (2) Bouchard, R.W., Jr. (2004). Guide to aquatic macroinvertebrates of the Upper Midwest. Water resources Center, University of Minnesota, St. Paul, MN. 208 pp.

    (3) Costa, C., S. A. Vanin, and S. Ide. (1999). Systematics and bionomics of Cneoglossidae with a cladistic analysis of Byrrhoidea sensu Lawrence and Newton (1995) (Coleoptera, Elateriformia). Arquivos de Zoologia, 35(3): 231-300.

    (4) Ross, R. M. (2008). Response of macroinvertebrate communities to remediation-simulating conditions in pennsylvania streams influenced by acid mine drainage. Environ Monit Assess, 323, 329-335.

    (5) Lee, C. (2007). Phylogeny of psephenidae (coleoptera: Byrrhoidea) based on larval, pupal and adult characters. Systematic Entomology, 32, 502–538.

    (6) Hinton, H. E. (1966). Respiratory adaptations of the pupae of beetles of the family psephenidae. The Royal Society, 251(771), 211-245.

    (7) Jackson, PD (1978) . Benthic Invertebrate Fauna and Feeding Relationships ofBrown Trout, Salmo trutta Linnaeus, and River Blackfish, Gadopsis marmoratus Richardson, in the Aberfeldy River, Victoria. Australian Journal of Marine and Freshwater Research 29 , 725–742.

    (8) Miller, M. P. (2002). Correlations between observed dispersal capabilities and patterns of genetic differentiation in populations of four aquatic insect species from the arizona white mountains, u.s.a.