Adults: Adult predaceous diving beetles are typically black or dark brown, sometimes with lighter stipes or spots. The body is smooth, hard and oval in shape. The hind legs are flattened and fringed for swimming. The antennae are threadlike and are usually less than the length of body. They range in size from 1/16 inch to almost 2 inches long.

Larvae: Larval predaceous diving beetles have elongate bodies and sickle-shaped mouthparts. They have two filaments on the end of the abdomen lined with feathery gills. Their antennae are threadlike.

Habitat: Common in ponds, lakes, rivers and quiet streams.

Ecology: Predaceous diving beetles are some of the most common of all aquatic beetles and are important members of most freshwater ecosystems. Both adults and larvae are aquatic. Adults swim by moving their hind legs like oars; occasionally they fly to other water bodies at night, and may be found around lights far from water. The larvae are sometimes called “water tigers”. Both the larvae and adults are ambush predators that feed on other aquatic arthropods and small aquatic animals (including fish and tadpoles). The diving beetle has strong, sharp jaws that are used for defense and to catch prey. Its hollow jaws are like hypodermic needles and can inject digestive enzymes into the beetle’s prey. The enzyme predigests the food before the beetle sucks it up. Because they lack gills, adult beetles must sporadically come to the water’s surface tail-end up in order to replenish their air supply. they may carry a bubble of air when they dive.

Life History: Four developmental stages: egg, larva, pupa, adult (complex, or complete, metamorphosis); adult females attach eggs to underwater plants; upon hatching, larvae are free-swimming, are fully aquatic, and molt (shed their body covering) several times before leaving the water to pupate underground near the water; adults emerge in warm months, and are the overwintering stage for most species