The qiumou is the swimming crab, a kind of large sea crab.
Tips
history
蛑 is not used alone in modern Chinese. It appears chiefly in the bound name 蝤蛑 (qiúmóu), the swimming crab. An older sense, shared with 蟊, was a root-eating pest.
register
Classical and dialectal; the common word for the crab today is 梭子蟹.