Sidewinder - Saidowinder (English spelling) sidewinder

A snake of the Viperidae family of the Squamata order of the Reptilia class. It is a venomous snake of the Viperinae subfamily known for its sideways movement, and is also known as the side-by-side rattlesnake. It is found in the southwestern United States and northwestern Mexico. It is 50 to 80 centimeters long, and is small for the Rattlesnake genus. The back of the body is gray-brown or yellowish brown, with dark brown horizontal stripes along the back line. The head is triangular, with a deformed horn-like protrusion of the supraorbital plate (a type of scale) above the eye, and a sound-making organ unique to rattlesnakes at the end of the tail. It lives in sandy semi-desert areas with sparse vegetation, and feeds on mice and lizards. During the day when the temperature is high, it burrows into the sand in the shade of shrubs, with only its eyes sticking out. The protrusion above the eye helps to keep the eye from getting covered in sand. To move on slippery sand, they bend their body into an S-shape and move sideways, a technique unique to this species called "sideways movement." This is a complex movement that is difficult to illustrate, as they always keep two points of their body on the ground and shift these points of contact. As they move across the sand, the trail of their contact points is left behind as parallel lines.

[Takahiro Matsui]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

爬虫(はちゅう)綱有鱗(ゆうりん)目クサリヘビ科のヘビ。横ばい運動で知られるマムシ亜科の毒ヘビで、別名をヨコバイガラガラヘビという。アメリカ合衆国南西部、メキシコ北西部に分布する。全長50～80センチメートルで、ガラガラヘビ属としては小形。体背面は灰褐色または黄褐色で、背中線上に暗褐色の横縞(よこじま)模様が並ぶ。頭部は三角形で、目の上に眼上板（鱗板の一種）の変形した角(つの)状突起があり、尾端にはガラガラヘビ特有の発音器官をもつ。植物がまばらに生えた半砂漠地帯の砂地に生息し、ネズミ・トカゲ類などを食べる。気温の高い日中は低木の茂みの陰で砂の中に潜り、目だけ出している。目の上の突起は、目が砂をかぶらないために役だっている。滑りやすい砂地での移動は、体をS字状に曲げて横に進むという、本種特有の「横ばい運動」による。これはつねに体の2か所を地面につけ、この接地点をずらしていく方法で、図説しにくい複雑な運動となっている。砂地を移動する接地点の軌跡は平行した線模様となって残る。

［松井孝爾］

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