1. The mandibles are usually lost, the labrum is reduced to a narrow transverse sclerite, and the labium is a small flap ( though its palps retain quite large).
   上颚消失，上唇退化为一条窄横片，下唇退化为一小片（下唇须发达）。

声明：以上例句、词性分类均由互联网资源自动生成，未经过人工审核，其表达内容亦不代表本软件的观点；若发现问题，欢迎向我们指正。