insect, bug, temper
蟲 centers on small crawling or creeping creatures: insects and bugs. The 'temper' sense is an archaic or extended use, possibly related to the idea of being 'bugged' or irritated, but the primary idea is a multitude of insects.
蟲 is the traditional form of 虫, originally depicting a snake or worm. The modern form triples the insect radical 虫 to emphasize a swarm or multitude of insects.
Three insects (虫) piled together: imagine a writhing mass of bugs, making the idea of 'insect' or 'swarm of insects' unforgettable.
For チュウ, picture a huge swarm of insects forming the shape of a 'chew' (チュウ) as they devour a leaf: chew -> チュウ, and the bugs are chewing.