SPECIES ID / Invertebrates

Water Beetles

Predaceous Diving Beetles

  • 509 species in North America
Phylum: Arthropoda`
Class: Insecta
Order: Coleoptera
Family: Dytiscidae

Identification Tips:

• Can be very large; to 70 mm
• Jaws include 2 large piercing fangs
• Legs long and slender with 5 segments ending in 2 claws
• Abdomen narrows to a distinct point

• Large bodied; to 50 mm in Fraser Valley
• Body hardened and convex on top and bottom (Water scavenger beetles are concave on bottom)
• Often rest hanging into water with tip of abdomen at surface
• 2 long antennae
• Short finger-like mouth parts, not visible from above

Life History:

• Primarily found in shallow, weedy, still water
• Live for 2 to 3 years

• Larvae climb on plants and debris
• Predatory; inject prey with digestive juice, and suck out dissolved tissue
• Breath air through valved openings at back of abdomen and through skin

• Adults are strong swimmers
• Prey on variety of invertebrates and small fish and amphibians
• Do not inject digestive juices, tear prey apart
• Carry air bubble under wings while diving

Very Sensitive Somewhat Sensitive Facultative Somewhat Tolerant Very Tolerant
    Most Some  

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