Giant Water Bugs

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True Bugs, Pacific Northwest

Giant Water Bug
Giant Water Bug, Photo By Bud Logan

Giant water bugs have a very unique appearance and are difficult to confuse with most other kinds of insects. Resembling a cross between a cockroach and a praying mantis, these bugs are brown and flat with large front legs used to grab and hold on to prey. Although they are sometimes called a giant water beetle, they are not beetles but are true bugs.

There are a few species of the closely related water scorpions that resemble them, but water scorpions always have a long, non retractable breathing tube at the ends of their abdomens. These bugs have a breathing tube as well, but it is much shorter and is usually retracted into the abdomen.

Although some giant water bugs are very large, over 8.5 cm not all species in this family are giants. In fact, the most commonly encountered giant water bugs are only about 2.5 cm. The one on this page was a giant one, about 8 to 9 cm.

Giant Water Bugs Larvae
Giant Water Bug Larvae, Photo By Bud Logan

Like all members of the order hemiptera, giant water bugs go through a simple metamorphosis from egg, to nymph, and then to adult stages.

During warm months, female giant water bugs attach eggs to underwater vegetation or in some species, stick eggs to the backs of males. Then the male will carry the eggs until they hatch. After hatching, the wingless nymphs resemble small, wingless adults.

They molt several times before becoming full sized, winged adults.

Giant water bugs are aquatic predators that are found in ponds, slow moving streams, and wetlands on Vancouver Island. They feed on many aquatic vertebrates and invertebrates, including minnows, tadpoles, frogs, and other aquatic insects.

Giant water bugs are primarily ambush predators who wait with front legs outstretched in aquatic vegetation near the water surface. When a meal swims too near, the giant water bug grabs it and pierces it with its sharp beak, quickly injecting it with paralyzing fluids and digestive juices. Although giant water bugs are fierce predators, they are often eaten by fish and larger predatory insects and spiders.

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