A good old favorite feature on Wizards' site is now back for 4E!
Vicious Venues: Fungi Thicket
It's a pretty interesting and comprehensive scenario which details on how to insert it in your adventure, to traps and what sort of creature that would live in a Fungi Thicket.
This scenario is designed for level 3-6 characters.
It's a pretty interesting read and you'll find stats for the Firebettle!