Water Beetles

Aquatic beetles look very similar to terrestrial beetles and live in water as both adults and larvae. They often have swimming hairs on their legs and more streamlined bodies. They have not lost their ability to fly despite spending most of their lives in water and are often found around bright lights at night. Their ability to fly lets them disperse to new water bodies. A couple of the more commonly seen water beetles are featured below.

Three-punctured Diving Beetle
Cybister tripunctatus

Three-punctured Diving Beetle, Cybister tripunctatus Three-punctured Diving Beetle, Cybister tripunctatus Whirligig Beetle, Macrogyrus oblongus Whirligig Beetle, Macrogyrus oblongus

Biology

This species live in lakes, dams and riverine pools throughout Australia, except for the south coast and Tasmania. It is also widespread in southern Asia and Africa. It is a fast-swimming predator that sometimes nibbles swimmers sitting quietly in the water. It bobs to the water surface regularly to renew the air bubble that it carries beneath its wing-covers.

Identification

Length about 30 mm. The polished, streamlined body is olive-green with a yellow border. This is one of the largest of more than 185 Australian species of water beetles belonging to the Family Dytiscidae.

Whirligig Beetle
Macrogyrus oblongus

Biology

These aquatic beetles swim in groups on the surface of water, often with a rapid circular motion. Each eye is divided into two separate parts — one for viewing above water, the other for scanning underwater. This species is widespread in eastern Australia, preferring quiet pools in shaded streams.

Identification

Length about 10 mm. The flattened body is greenish-black with long forelegs and short midlegs and hindlegs. This is one of 25 Australian species of whirligig beetles that belong to the Family Gyrinidae.

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