What's That Bug? does not endorse extermination

Subject: Swimming pool bug
Location: Canberra Australia
October 22, 2015 9:58 pm
Hi Bugman.
I left my above ground swimming pool uncovered for approx. 6 months over winter. I didnt clean it nor did I add any chlorine. Now that its getting warmer I thought time to clean it out and start getting it healthy again. When doing so I caught 11 of these swimming bugs and I just needed to know more.
They swim to the water surface and sit there facing downwards (with the backsides toward the top).
When I stir the water they dive to the bottom (approx. 600mm) where I can’t see due to the leaves and other garbage – then do not come up for at least 5 minutes.
They appear to have 6 legs, two tails (split) and two clippers or claws on their face. They are very good at staying absolutely still, but when they swim they have a fish like turning movement. It should be noted that when I pulled them out of the water, they had no troubles walking around, moving almost like a scorpion.
I have attached a video and some pics.
This is in Canberra, Australia. Currently October (middle of spring) and heading towards summer.
Appreciate if you had any ideas on what these are?
Signature: thank you

Water Tigers

Water Tigers

These are Water Tigers, the aquatic larvae of Predaceous Diving Beetles in the family Dytiscidae.  There is a nice simple explanation of the life cycle of the Predaceous Diving Beetles on the Australian Museum website where it states:  “Larvae have a siphon (like a snorkel) coming out the end of their body. They stick this siphon out of the water to get oxygen to breathe.”  According to the Missouri Department of Conservation site:  “Larvae, called ‘water tigers,’ are elongated, flattened and can be 2 inches long. They commonly come to the surface to draw air into spiracles (like snorkels) located at the hind end of the body. There are 3 pairs of legs, and the jaws are strong pincers that are used to grasp prey.”  The Natural History of Orange County, California site has some nice images of Water Tigers.  As you can tell by our links, Predaceous Diving Beetles are found in many places on the globe.

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What's That Bug? does not endorse extermination
Location: Canberra, Australia
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