Bipalium - Bipalium (English spelling)

A general term for animals in the phylum Platyhelminthes, class Turbellaria, family Bipalidae. A type of flatworm that lives on land, the name "flatworm" comes from the fact that the shape of its head resembles the shape of a Japanese hairpin. It is common in tropical and subtropical forests such as Southeast Asia, but some species are also found in temperate zones. It is 5-12 cm long and 2-4 mm wide, and is long and slender. Its back is black or blackish orange, and some species have one or three black lines. Its head is flat and extends horizontally in a crescent shape (so-called hairpin shape), and its neck is thin. Numerous eye spots are lined up along the edges of the head and neck, but cannot be seen with the naked eye. Its mouth is in the center of its ventral surface. It is mainly active at night, but during periods of relatively high temperature and humidity, it can be seen crawling slowly on the ground, under stones, or in greenhouses during the day. The mark it leaves behind is left with mucus, and if it comes into contact with the body it breaks into several pieces (autotomy) making it difficult to handle.

The common species in Japan is the black-striped billworm, Bipalium fuscatum , which is about 10 centimetres long. It can be seen on the road, in gardens and kitchens after rain, crawling with the front edge of its head moving in a wavy pattern. The three-striped billworm, B. trilineatum , is 4-5 centimetres long, has a deep orange-yellow back with three vertical black lines. Recently it has been seen in greenhouses, but it lives on the damp ground or under stones in the mountains and fields. Billworms are sometimes mistaken for "pollution bills" due to their name, but they are harmless.

[Minegishi Hideo]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

扁形(へんけい)動物門渦虫(かちゅう)綱コウガイビル科Bipalidaeの動物の総称。陸上生活をするウズムシ類で、コウガイの名は、頭部の形が日本髪の笄(こうがい)の形に似ていることから生じている。東南アジアなど、熱帯、亜熱帯の森林に多いが、一部は温帯にも分布する。体長5～12センチメートル、幅2～4ミリメートルで、細長い。背面は黒色か、黒みがかった橙(だいだい)色で、種類によっては1本または3本の黒線がある。頭は扁平で横に半月形に伸び（いわゆる笄の形で）、頸部(けいぶ)は細い。多数の眼点が頭部や頸部の縁に沿って並んでいるが、肉眼ではわからない。口は腹面の中央にある。おもに夜間に活動するが、比較的高温高湿の時期には、昼間でも地上や石の下、温室内などをゆっくりはっているのをみかける。はった跡には粘液がつき、体に触れると数片に切れて（自切）扱いにくい。

　日本の普通種は、クロイロコウガイビルBipalium fuscatumで、体長10センチメートルぐらい。雨上がりの路上や庭、台所などでみられ、頭部の前縁を波状に動かしてはう。ミスジコウガイビルB. trilineatumは、体長4～5センチメートル、背面は濃い橙黄(とうこう)色で3条の黒線が縦走する。最近は温室などでもみかけられるが、山野の湿気のある地上や石の下などにすむ。コウガイビルはその名を「公害ビル」と誤認されることがあるが、無害である。

［峯岸秀雄］

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