Giant Water Bug


“Come here!  You have to see this big ugly bug!”

The excitement and disgust was evident as I was hustled out the campus building to a corner of the foundation by a security light.  There on the sidewalk was a large beetle, two inches or more long, with a dull brown body with noticeable folded up wings.  It had a long narrow body, a comparatively small head, and two massive front legs obviously modified for grasping prey.

It was not a predaceous diving beetle.  They are generally smaller, have a more oval body form, and are often a shiny black, with no obvious wings.  It was a giant water bug.

Giant water bugs are widely distributed in slow or stagnant water such as lakes, ponds, marshes, and slow-moving rivers and streams where they hide out among the vegetation, rocks, or similar cover.    This particular bug was a long way away from water.  They are powerful fliers, but seem to become disoriented by bright lights at night such as street lights and security lights.  I suspect that was the case here.

The life cycle of these insects is a bit unusual.  Females lay their eggs above the water on emergent vegetation such as cattails or bulrushes.  Then, rather than leaving them alone, the males proceed to guard the eggs as they develop.  After about two weeks the eggs hatch into nymphs which go through several growth or developmental stages, shedding their skin each time, before morphing into adults.

Both nymphs and adults are fierce predators.  They feed on a variety of aquatic invertebrates, tadpoles, minnows, and small fish.  They are even known to take much larger prey such as frogs and snakes.  They attack or ambush their prey, and fiercely grasp on to it with their powerful front legs.  Once in the firm grasp, the prey is injected with venom which in addition to killing the prey, also liquefies the internal organs which are subsequently ingested through the bug’s sucking mouth parts.

If you are of the habit of walking around in a body of water with your bare feet, you might want to reconsider. Giant Water bugs are also known as “toe biters.” Apparently, these bites can be quite painful.  Really painful based on some of the accounts I have read.

Chuck Lura

Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Dakota College at Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.

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