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Water Penny (Psephenus spp.)


Detailing the physical features, habits, territorial reach and other identifying qualities of the Water Penny.




Water Pennies have larvae that look more like crustaceans or fossils than beetles.



 Updated: 5/19/2020; Authored By Staff Writer; Content ©www.InsectIdentification.org




An adult Water Penny looks like many types of beetle: six legs, black body, shiny, and small. Its larval stage looks quite unlike most beetle larvae. Instead of a worm-like, white grub with a brown head curling in the soil, this larva looks like a legless oval and is aquatic. Its copper color, round shape, and water habitat helped coin its common name. It is often compared to a trilobite, whose fossil is a similar shape with armor plating. Young Water Pennies are often found clinging to underwater stones and rocks in well-circulated streams, rivers, and lakeshores. They may even hold fast to sunken wood. Feathery gills allow them to breathe. Legs are hidden under the ‘shell’ and have scrapers used to nibble algae on the substrate they adhere to. They also eat decaying organic matter in the water. Once in adult form, they live on land, but near the water they came from.

The presence of Water Pennies signifies good water quality. In unhealthy, polluted streams that have overgrown algae or deep sediment, their ability to cling to stones and rocks is compromised, so they cannot establish a population. Looking for Water Pennies in shallow water can be fun for those who don’t mind getting their feet wet.


General Characteristics
Rounded insect body icon


Taxonomic Hierarchy
Kingdom: Animalia
  Phylum: Arthropoda
    Class: Insecta
      Order: Coleoptera
        Family: Psephenidae
          Genus: Psephenus
            Species: spp.
Identifying Information
Scientific Name: Psephenus spp.
Category: Beetle
Size (Adult; Length): 4mm to 6mm (0.16in to 0.23in)
Colorwheel Graphic Colors: brown; black
Descriptors: round; shell; stuck; horseshoe crab-like; underwater; fossil; trilobite
Territorial Map
Alaska  
Hawaii  
Prince Edward Is.  
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Territorial Reach (A-to-Z)
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
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Alberta
British Columbia
Manitoba
New Brunswick
Newfoundland and Labrador
Nova Scotia
Ontario
Prince Edward Island
Quebec
Saskatchewan
Mexican National Flag Graphic
Mexico
Note: An insect's reach is not limited by lines drawn on a map and therefore species may appear in areas, regions and/or states beyond those listed above as they are driven by environmental factors (such as climate change), available food supplies and mating patterns. Grayed-out selections indicate that the subject in question has not been reported in that particular territory. U.S. states and Canadian provinces / territories are clickable to their respective bug listings.




Beetle Anatomy
Graphic showing basic anatomy of a common North American Beetle insect
1
Antennae: Beetles have a pair of antennae on the head used as sensors.
2
Head: The head is home to the insect's eyes, antennae, and mandibles (jaws).
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Thorax: Holds the three pairs of legs as well as vital internal organs.
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Elytron: One of two wing cases on a Beetle that protects its wings (plural: elytra).
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Wings: Appendages used for flying and kept under the elytra until needed.
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Abdomen: Houses organs related to circulation, reproduction, and excretion.
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Legs: Beetles have three pairs of legs located at the thorax, numbering six legs in all.