Giant Water Bugs

A video by Walter Jahn

Giant water bugs have a 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 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 Bug, Vancouver Island, BC
Giant Water Bug, Vancouver Island, BC, 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 Bug Larvae, Vancouver Island, BC
Giant Water Bug Larvae, Vancouver Island, BC, Photo By Bud Logan

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.

A message from Bud

15 thoughts on “Giant Water Bugs”

  1. I just found one at my place on Hornby Island. It was struggling to walk through the grass so I let it crawl onto my hand and put it into one of the water barrels we have on the property. We don’t have a pond. I put in some grape leaves for it to shelter under. Lots of mosquito larvae for it to eat.

  2. We had one land on us whilst we sat on the deck late at night around the firepit in Brentwood Bay. It was huge….. approx 8-10cm in length.!!

    We captured it and released into a local lake….. we have pics too….

    Scared the crap out of us…!!

  3. It says they live on the Island but how far does their range spread?
    I’ve seen multiple specimens in the Vernon and Salmon Arm area as a kid. Almost ran one over with my bike. Never seen one in GV area though.
    Never even knew they were on the Island actually. Very interesting creature to see in action.

    1. Hi Tyler, these giants have a very large range, they cover most of Canada and the USA except for the southern parts. I have seen them on all parts of Vancouver Island including Victoria.

    2. We found one of these giant water bags in North Vancouver tonight…kids were playing soccer near Mosquito Creek / Delbrook.
      It landed on the field…was quickly removed and let go in the bushes.
      Never seen anything like this before

    3. I just found one today at my farm in Victoria BC! It literally fell from the sky (the roof) and landed on my horses butt and scared him half to death he almost jumped into my arms!

  4. Is there a species of Giant Water Bugs that live in Saltwater around Nanaimo area in the Straight of Georgia ?

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