labrum

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).

颚消失，唇退化为条窄横，唇退化为（唇须发达）。

The experiment is such: Researcher uses foam rubber or plastic from the female alar collect secretion, dissolve is in at the inunction after alcohol the labrum of a few females.

研究人员用海绵从女腋收集分泌物，溶于酒精后涂擦在些女唇。