Taikouchi (English spelling) water scorpion

A general term for insects belonging to the order Hemiptera, suborder Heteroptera, family Nepidae, or one of these. A type of aquatic stink bug, with a flat, long-oval body (Nepidae) or rod-shaped (Aquatic Mantis). The proboscis is short and needle-like, and the antennae are also very small. At the end of the abdomen there is a long breathing tube with an extending tail-like process. The breathing tube does not extend or retract, which makes it different from the family Bucconidae. The front legs are sickle-shaped and serve as capturing legs, while the middle and hind legs are long and slender and serve as swimming legs. There are about 200 known species around the world, mainly in tropical regions, with six species native to Japan.

Its Japanese name is Laccotrephes japonensis , and it has a flat, elongated body with a length of 35-40 mm. Its breathing tube is long and almost equal to the body length. Its entire body is dark brown, and usually has mud on its surface. It is found from Honshu to Taiwan, and lives in shallow waters such as the water's edge of ponds and marshes. It rests on the muddy bottom and preys on small fish and tadpoles that approach. If you catch it and take it out of the water, it pretends to die. It gets its name from the fact that it moves its retracted front legs alternately, as if beating a drum. A closely related species is the small-headed lion's lion, Nepa hoffmanni , found from Aichi Prefecture to Hyogo Prefecture. It is smaller and rounder than the lion's lion, with a body length of about 20 mm. Its breathing tube is very short, about one-eighth the body length. It lives among moss or under fallen leaves in wetlands.

[Masami Hayashi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

昆虫綱半翅(はんし)目異翅亜目タイコウチ科Nepidaeに属する昆虫の総称、またはそのなかの1種。水生カメムシの仲間で、体は平たい長卵形（タイコウチ類）あるいは棒状（ミズカマキリ類）。口吻(こうふん)は針状で短く、触角もきわめて小さい。腹端には、尾状突起が伸びた長い呼吸管をもつ。呼吸管は伸縮せず、この点でコオイムシ科と異なる。前脚は鎌(かま)状で捕獲脚となり、中脚と後脚は細長く、遊泳脚となる。熱帯地方を中心に世界で約200種が知られ、日本産6種。

　和名タイコウチLaccotrephes japonensisは、体長35～40ミリメートル、体は扁平(へんぺい)で長形。呼吸管は長く、体長とほぼ等長。体全体が暗褐色で、普通、表面に泥をつけている。本州から台湾にかけて分布し、池沼の水際などの浅い水中にすむ。底の泥上に静止し、近づく小魚やオタマジャクシなどを捕食する。手で捕まえて水から出すと擬死を装う。縮めた前脚を交互に、太鼓を打つように動かすので、この名がある。近縁種には愛知県から兵庫県にかけて分布するヒメタイコウチNepa hoffmanniがあり、タイコウチより小形で丸みがあり、体長約20ミリメートル。呼吸管は非常に短く、体長の約8分の1。湿地のコケ間や落葉下にすむ。

［林　正美］

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例