From Monkey Island wiki
The Flotsam Jungle covers most of Flotsam Island. It is known to be somewhat of a labyrinth, being easy to get lost in. The jungle is extremely noisy, with all of the noises of the animals that inhabit it. In "Launch of the Screaming Narwhal", Guybrush Threepwood uses these various animal sounds to navigate through the jungle.
The jungle hides some ancient Vaycaylian ruins from the time, centuries before, when the merfolk tried living on land. The largest monument to this time is a stone statue of figure playing a horn, which can be used to control the winds; hence it is named as the Vaycaylian Wind Control Device. There are several idols scattered throughout the jungle; when they are arranged to represent certain wind gods the wind is changed. It is uncertain whether the Vaycaylians employed advanced technology to operate the device from a distance or whether the unseen wind gods actually play a part.
The jungle is where the Voodoo Lady is found living in a hut. It is also the home of the Flotsam Island Jungle Beast, a mysterious carnivore whose legend is perpetuated by Hemlock McGee. The Marquis De Singe's lab shows that he has studied some of the jungle's insect life, including fireflies and moths. Near the end of "The Trial and Execution of Guybrush Threepwood", the Wind Control Device in the jungle is also the location of the final sense of an "after-dinner belch" in the Feast for the Senses needed to enlarge La Esponja Grande, and a place for Guybrush's and De Singe's final confrontation, right before Guybrush gives the sponge the final sense, making it powerful enough to absorb the Pox of LeChuck from Elaine and everyone else across the entire Gulf of Melange. However, the jungle is also the place where Guybrush meets his untimely demise at the hands of LeChuck, who regains his voodoo zombie form from the legendary sea sponge.