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Bug Bytes: Predaceous Diving Beetles

Predaceous diving beetle
Lynette Schimming - used with permission
Predaceous diving beetle.

Standing by a pond and gazing into the water, you can find all sorts of creepy crawlies on and under the surface. And if you look very closely, you might even spot a tiger — a water tiger, that is.

As highly skilled predators, predaceous diving beetles can make easy meals of a wide variety of prey. But it’s their larvae that have the fierce reputation earning them the nickname “water tigers.”

Armed with an impressive pair of sickle-like jaws, the larvae can make meals of animals much larger than themselves, including other insects, worms, leeches, mollusks, tadpoles and small fish.

Although the adults and larvae live primarily in and under the water, neither have gills. They need to breathe air. If you patiently observe them, every once in a while you’ll see them come to the surface for a breath. But they have very different ways of doing so.

The larvae breathe by sticking a straw-like tube at the end of their abdomen above the surface — sort of like having a built-in snorkel.

The adults employ a different strategy. They approach the surface butt first, trapping a bubble of air between their wing covers and abdomen. In a way, they create their own SCUBA tank, allowing them to spend a long time underwater.

Predaceous diving beetles can be found in almost every kind of freshwater habitat, although less common in faster streams and rivers.

So, the next time you’re by a pond or slow-moving stream, be on the lookout for the variety of interesting insects you might find on and under the surface of the water.

And if you’re lucky, you might just spot a tiger.

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