at least 160, see text

The predaceous diving beetles (also spelled "predacious") are a family (Dytiscidae) of water beetles. They are about one inch long, dark brown in color with golden highlights and short, but sharp, pincers. The larvae are commonly known as water tigers. The family has not been comprehensively cataloged since 1920, but is estimated to include about 4,000 species in over 160 genera.

When still in larva form, the beetles vary in size from a half an inch to two inches. Their bodies are shaped like crescents, with the tail long and covered with thin hairs. Six legs protrude from along its belly, which also sports the same thin hairs. The head is flat and square, with a pair of long, large pincers. When hunting, they tend to cling to grasses or pieces of wood along the bottom, and hold perfectly still until prey passes by- at which point, they lunge, trapping their soon-to-be-food between their front legs and biting down with its pincers if the prey is large, and merely biting at the water if it is small. Usual prey includes tadpoles and glassworms, among dozens of other smaller water-dwelling creatures.

As soon as the beetles come to the stage in life in which they mature to adulthood, the larva crawl from the water on their aforementioned sturdy legs, and bury themselves in the mud for around a week; upon the end of this period, they emerge from the mud as adults.

Genera

• Hydrotrupinae
  • Hydrotrupes
• Copelatinae
  • Agaporomorphus
  • Aglymbus
  • Copelatus
  • Lacconnectus
• Agabetinae
  • Agabetes
• Laccophilinae
  • Laccophilus
  • Laccodytes
• Hydroporinae
• Laccornini
  • Laccornis
• Vatellini
  • Derovatellus
  • Macrovatellus
  • Mesovatellus
  • Vatellus
• Methlini
  • Celina
  • Methles
• Hydrovatini
  • Hydrovatus
  • Queda
• Hyphydrini
• Bidessini
• Hydroporini
• Colymbetinae
• Agabini
• Coptotomini
• Matini
• Colymbetini
• Dytiscinae
• Dytiscini
  • Dytiscus
  • Hyderodes
• Hydaticini
• Aciliini
• Eretini
• Cybistrini
  • Cybister
  • Megadytes