Animal Species:Giant Water Bug

These bugs are formidable underwater predators. When hunting, Giant Water Bugs breathe using a syphon at their rear end which acts like a snorkel

Giant Water Bug

Giant Water Bug
Photographer: Andrew Donnelly © Australian Museum

Standard Common Name

Giant Water Bug

Alternative Name/s

Electric Light Bug; Giant Fishkiller


These bugs, are the giants of the bug world - adults may be up to seven centimetres long.

Size range

7 cm


Giant Water Bugs are found in eastern Australia and the Indo-Pacific.


Giant Water Bugs live in fresh water, usually in still waters such as lakes.

Feeding and Diet

The Giant Water Bug positions itself head-down on a submerged plant stem and hunts by ambush, taking tadpoles, small fish, frogs, snails and aquatic insects. It catches prey with its grasping forelegs before piercing the body with its sucking mouthparts.

Other behaviours and adaptations

They fly between hunting sites and are attracted to lights, including car headlights. They are known to occasionally bite humans when disturbed - a very painful experience.



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Tags bugs, insects, invertebrates, identification, wildlife of sydney, arthropods,


mplucke - 9.04 PM, 18 April 2012
We took this photo at Inverell NSW 14/1/12. It had been a dry few months but rained that night, this beastie was under the light at the RSM club, against the wall of the walkway. The kids thought it was some sort of cicada until it waved it's pincers at us when proded with the room key. It took us quite a long time to find out what it was as we had never seen these before! Just as well the kids got dragged away & didn't get close enough to get bitten!
chamz5 - 11.04 AM, 13 April 2012
This one was found on the side of my truck-trailer. The trailer came from Ormeau, south east QLD. The trailer had not stopped from Ormeau untill it reached Clybucca, 5 hrs from Ormeau! I have attached a pic. The bug was not kept, nor harmed, It was coaxed onto a ruler then then placed onto grass by a braver soul than me! It seemed very slow & docile (The other truck driver & bug!) I would estimate that the body of the bug was approx 7cm long x 5cm wide! Cheers!

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David Britton - 9.03 AM, 26 March 2012


Shane Ahyong who is a research scientist at the Museum has kept these insects as pets.

His advice is as follows:

Giant Water Bugs will each almost anything from insects to small yabbies, small frogs and fish. In captivity, feeding the bugs, grasshoppers or crickets (either catch your own or from a pet store) two or three times a week is ideal. They will eat other insects too, such as moths and cockroaches, but the crickets and grasshoppers leave less mess in the aquarium. It is important to remove the carcasses of the prey once the bug has finished feeding in order to prevent fouling the water.  It is also good to include some water plants or rocks for the bugs to cling to when at rest. It’s also best not to keep more than one in the tank as they will often cannibalise each other. Lastly, keep a lid on the tank to prevent them climbing out.  

vandreao - 11.03 AM, 25 March 2012
My partner has these bugs at his workplace, where they regularly dive bomb the staff. (they work at a shipyard in Cairns, Queensland) he has recently bought one home for our son, and set it up in a tank. We have fed him a cockroach which he greedily ate, but I am wondering how often we should feed him. Any ideas? Cheers
David Britton - 9.02 AM, 06 February 2012

Hi Sioux,

They should be abundant and all-year round residents in Lismore.


sserendipityy - 9.02 PM, 04 February 2012
i found one of these (dead) this week in a garden in Lismore; it took me a while to identify it, firstly thinking it belonged to the beetle family. Do you think a bird could've dropped him or is all this rain affecting their locations?
amcalpine - 2.04 PM, 30 April 2011
Looks like he could just snap the pen in half!! :)

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amcalpine - 2.04 PM, 30 April 2011
I found one of these today 30/04/2011 at Moomba in the Cooper Basin; Far North East of SA. Glad I took care when handling him having now read about his bit. Fair indication of the amount of rains/flooding over the last 12 months, an aquatic bug in the middle of the desert!

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