Back swimmer (pine weed) - Back swimmer (English spelling)

Japanese: マツモムシ(松藻虫) - マツモムシ（英語表記）back swimmer

An insect of the Hemiptera family, family Culicidae (illustration). It was probably named after the fact that it lives in waters where aquatic plants such as seaweed grow. In addition, because it stores a large amount of air on its ventral surface, its center of buoyancy is on the ventral side of its center of gravity, so it swims with its belly up, which is why it is called a backstroke insect in Europe and the United States. It is a boat-shaped insect with a yellow body and large black spots, with a body length of about 13 mm, and its hind legs are long and oar-like with a well-developed row of swimming hairs. It dives underwater and stays still on aquatic plants using its four front legs, but it usually floats on the surface of the water, with the front and middle legs and tail touching the water surface, and its body held at an angle underwater.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

半翅目マツモムシ科の昆虫（イラスト）。マツモなどの水草の生えた水中にすむことから名付けられたものであろう。また腹面に多量の空気を蓄えているため，浮心が重心より腹側にあるため腹を上にして泳ぐので，欧米では背泳ぎ虫と呼ばれている。黄色に大きな黒斑のあるボート形の虫で，体長13mm内外，後脚はオール状で長く，発達した遊泳毛列を備える。水中に潜って，前方の4本の脚で水草などに静止するが，ふだんは水面に浮かんで，前･中脚端と尾端を水面につけ，体は水中で斜めに保たれている。

出典　株式会社平凡社世界大百科事典第２版について　情報

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