Common Names: Aquatic beetle, diving beetle, water scavenger beetle
Scientific Name: order Coleoptera, family Dytiscidae
Aquatic beetle larvae inhabit both still and running water, where they feed on other insects. The act of predation often exposes them and they became prey for trout. Larvae are available all summer, and you'd wouldn't be amiss if you tumbled an imitation down a river, or retrieved one near weedbeds in a lake.
Larvae pupate out of the water, so pupa patterns are not an option. However, the adults return to the aquatic world to prey on insects. Unlike the larvae, adults cannot live underwater; they carry an air bubble with them and must frequently return to the surface to get more air, much like a waterboatman . Fishing an adult pattern on a lift-and-settle presentation with a floating line makes good sense. In lakes, stick to water that's less than four or five feet deep and near weeds. In rivers, you're better off with larva patterns unless you're in a quiet area.
LARVA COLOR: Brown, olive, tan to light olive
ADULT SIZE: 3-25 mm (1/8 to 1 in)
ADULT COLOR: Black, brown
OTHER CHARACTERISTICS: Larvae have a broad head with distinct mandibles--beware, they bite! Adults have a pair of large legs for swimming.