杜

prefix: prefix in certain Teochew animal/insect names (e.g. 杜猴 mole cricket), to prevent; block (literary)
杜

杜 covers both a literary verb sense ('to prevent/block') and a Southern Min/Teochew-specific prefix used in animal/insect names (as in 杜猴, 杜蚓); it is unclear which better represents the single confirmed dou6 reading, so the animal-prefix sense was chosen given the surrounding batch of 杜-compounds.