Dytiscidae

June to October

Korea, Japan, China and Taiwan

It is around 35~40-millimeter-long. They have long ellipse body shape in greenish black color. In terms of the back, males’ one is smooth and gloss, and females’ is rough because of thin and short linear groove. Both ends of the forehead, clypeus, upper labrum, antennas, and whiskers on both sides are yellowish brown. Its elytra have yellowish brown bands along the outer margin and three spot-filled stripes. The lower part of the body is mostly yellowish brown, and the process of the prothorax, scales of the back of the thorax, and inner table of metacoxa are greenish black. Legs are mostly yellowish brown, and middle and tarsus of hind legs are blackish brown.

Imagoes and larvae are carnivorous by eating small creatures or fish in the water. They lay their eggs one by one in the stems of grasses in the water.