• 16 species known in North America

Identification Tips:

Highly flattened body; round or oval in shape
• Plates cover extend beyond body from most or all body segments
• Plates may overlap or have spaces between them
• 3 pair segmented legs and filamentous gills visible on under side
• 3-10 mm

• Near circular beetle just above water level on rock or wood with splashing water
• Usually in congregations

Life History:

• Larvae cling to rocks in riffles (fast flowing areas)
• Daylight hours usually spent underneath rocks; emerge at night to feed
• Graze on algae on rocks
• Mature larvae crawl out of water to sheltered locations to pupate
• Adults are short lived and seldom seen.
• Found at breeding sites; just above water level in fast flowing rocky areas of streams, often on rocks protruding from swiftly flowing, splashing water

Very SensitiveSomewhat SensitiveFacultativeSomewhat TolerantVery Tolerant
Pollution IndicatorSomewhat tolerant of metal pollution

Primary Information Source:
Voshell, J. Reese. 2002. A Guide to Common Freshwater Invertebrates of North America. McDonald and Woodward Publishing Company. Blacksburg, Virginia.