pygodidymus

例句：

1. 1.The pygidium is a unique feature of the spider's body.
   蛛体的独特特征是其腹部。
2. 2. The pygidium is used to store food and water for the spider.
   蛛体用于储存食物和水，供蜘蛛使用。
3. 3. The pygidium is also used as a protective covering for the spider's body.
   蛛体还用作保护覆盖蜘蛛身体的覆盖物。