Royal Alberta Museum: Invertebrate Zoology - Bug Facts

[Caterpillars and Other Immature Insects]

Fact Sheets: Commonly Observed and Asked About Insects and Spiders Found in Alberta

Giant Water Bug (Lethocerus americanus)

Giant Water Bug
Photo CD 0023 3291 1601, Image #17 - Credit: Terry Thormin

INTRODUCTION

The Giant Water Bug is one of the largest insects in Alberta, reaching 50 mm in length. Because it often turns up under street lights and porch lights, it is also one of the most asked about insects in Alberta. It is commonly mistaken for a beetle or even a cockroach, but is a true bug. Alternate names include toe biter because they can deliver a nasty bite, and electric light bug because they are attracted to lights.

IDENTIFICATION

Like all true bugs, the Giant Water Bug has piercing, sucking mouth parts, the short, pointed beak on the underside of the head. The other distinguishing characteristic is the fact that the wings overlap at the hind end of the abdomen, forming an X like pattern. Other than that, the sheer size of the insect and the unusual shape of the front legs help identify it.

DISTRIBUTION

The Giant Water Bug is found throughout the whole province wherever there is standing or gently running water.

TIME OF YEAR

Giant Water Bugs are active all year, but are most commonly seen in the late summer and early fall. At this time of year the adults are leaving the shallow ponds at night to look for deeper bodies of water where they can remain active throughout the winter under the ice. While thus searching, they are often attracted to lights such as porch lights, where people find them the following morning.

HABITAT AND HABITS

Giant Water Bugs like stagnant or slowly moving water, especially where there is emergent vegetation such as cattails. They usually grab hold of a plant near the surface, and stick their short breathing tube out of the water to allow them to breath while waiting for prey. With their powerful front legs they are able to grab prey as big as small fish, frogs and salamanders. They pierce their prey with their sharp beak and secrete enzymes that dissolve the body tissues, thus allowing them to suck up the resulting liquid.

SIMILAR SPECIES

There is only one species of Giant Water Bug in Alberta.

COMMENTS

Although not really dangerous, the Giant Water Bug can give one a nasty bite. One person described the bite as very painful, causing the finger and whole hand to swell up dramatically, to the point where they lost all use of the hand, and remaining thus for about two weeks. If you are going to handle this insect, it should be done with care.

[Royal Alberta Museum's Home Page] [Invertebrate Zoology]

For more information on this bug, please contact the Bug Room.
© Copyright 2000-2005, Royal Alberta Museum - ALL RIGHTS RESERVED
Last update: June 10 2005