64 Vipers

The family of snakes called vipers includes some of the deadliest poisonous snakes in the world. Some of the snakes in this fearsome group are the water moccasin, rattlesnake, and copperhead (all of which are found in the United States), the bushmaster and fer-de-lance of South America, and the puff adder of Africa.

Vipers have thick bodies, short tails, and triangular heads. Fangs in their upper jaws inject poison into their victims’ bodies like a hypodermic needle. When the snakes bite, they contract the muscles around their poison sacs. These sacs are located behind the eyes. The poison squirts out through the hollow fangs. Almost a half-teaspoon of poison is put into a victim at one time. Fortunately, many of these snakes are small, so their bite is not fatal.

There are actually two main types of vipers—the true vipers and the pit vipers. Pit vipers live in Asia and the Americas. The name comes from a small hollow in the side of the head just below the eye. The small hollow, or pit, has a special nerve that senses heat, helping the pit viper to find its warm-blooded prey. True vipers don’t have this special nerve and must rely on their keen sense of smell to find their food. Vipers don’t usually strike unless they are disturbed or are looking for food. Still, it is a good idea to stay away from them.

蝰蛇科包含世界上一些最致命的毒蛇。这个可怕的蛇类群体包括水蝮蛇、响尾蛇、铜头蛇（这些在美国都能找到）、南美洲的巨蝮和矛头蝮，以及非洲的鼓腹咝蝰。

蝰蛇有着粗壮的身体、短尾巴和三角形的头部。它们上颌的毒牙像皮下注射针一样，将毒液注入猎物的体内。当蛇咬击时，会收缩毒囊周围的肌肉，毒囊位于眼睛后方。毒液通过中空的毒牙喷射出来，一次就能向猎物注入近半茶匙的毒液。幸运的是，许多蝰蛇体型较小，所以它们的咬伤并不致命。

蝰蛇实际上主要分为两类：真蝰蛇和蝮蛇。蝮蛇生活在亚洲和美洲，名字来源于头部眼睛下方侧面的一个小凹陷。这个小凹陷（即颊窝）有一根能感知热量的特殊神经，帮助蝮蛇找到温血猎物。真蝰蛇没有这种特殊神经，必须依靠敏锐的嗅觉寻找食物。蝰蛇通常不会攻击，除非它们受到惊扰或正在觅食。不过，离它们远一点总是明智的。