Hydrophilidae; water scavenger beetle

Japanese: ガムシ（英語表記）Hydrophilidae; water scavenger beetle

A general term for insects of the family Hydrophilidae in the order Coleoptera. Most beetles are freshwater and some are terrestrial. Most of the bodies are ovate, strongly bulging on the back, smooth and shiny. The underside is flat. The head is short and fits inside the prothorax. The antennae are short and consist of 6-9 segments, the first of which is the longest and can be curved. The sixth segment is cup-shaped, and the three distal segments form a bulb covered with fine hairs. The mandibles are long and slender, and are the same length as the antennae or longer, which is a notable feature of this family. The mandibles are powerful and toothed. The legs are long, with five tarsals. Freshwater species have long hairs on their hind legs that are suitable for swimming. They are generally herbivorous, but many terrestrial species gather on animal dung and other decaying matter. There are about 2,000 species in the world, and about 75 species in Japan. The water beetle Hydrophilus acuminatus is the largest species of the Hydrophilidae family found in Japan, with a body length of 32-35 mm. The body is elliptical with slightly pointed wing tips. The whole body is shiny black, with the antennae and mandibles yellowish brown. The elytra have four rows of punctations. The midline of the middle and posterior thorax is prominently ridged, the posterior end of which is sharply needle-like. The midline of the abdominal segment is also ridged. It is often found in still water such as swamps and ponds, and feeds on aquatic plants. It is distributed throughout Japan south of Honshu, Korea, and China.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

鞘翅目ガムシ科の昆虫の総称。微小ないし大型の甲虫で大多数は淡水生，一部は陸生である。体は多くは卵形で背面が強くふくらみ，なめらかで光沢の強いものが多い。下面は平たい。頭部は短く，前胸の中に納まる。触角は短く，6～9節から成り，第1節は最長で湾曲することもある。第6節は杯状，先端3節は微毛におおわれた球稈を形成する。小腮枝が細長く，触角と同長またはそれ以上であることが本科の著しい特徴となっている。大腮は強力で有歯。肢は長く，跗節は5節。淡水生のものでは後肢に遊泳に適した長毛がある。一般に草食性であるが，陸生種には動物の糞やその他の腐敗物に集るものが多い。世界に約 2000種，日本に約 75種を産する。ガムシ Hydrophilus acuminatusは体長 32～35mmで日本産ガムシ科中の最大種。体は楕円形で翅端はややとがる。全体黒色で光沢があり，触角，小腮枝などは黄褐色である。上翅には4条の点刻列がある。中・後胸板の正中線は顕著な隆条になり，その後端は鋭く針状にとがる。腹節の正中線も隆条となる。沼，池などの止水に多くみられ，水草などを食べる。本州以南の日本全土，朝鮮，中国に分布する。

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