Because in the games, Bug-types are effective against Dark-types. Just like malaria in Africa.
Red
Cuz Pikachu might Pik a Chu
The elephants are using them as tampons
The parrot says, "Africa! There are loads of them running around!"
They were ravin' with Raven.
During a game of charades
Are you gonna Jaundice on Saturday
Malaryan Steel."