During the meeting, what frightens the little boy with the mulberry birthmark?

The boy with the mulberry colored birthmark states his fear of the "snake-thing" or "beastie" at the meeting.

“He wants to know what you’re going to do about the snake-thing.” Ralph laughed, and the other boys laughed with him. The small boy twisted further into himself.

“Tell us about the snake-thing.”

“Now he says it was a beastie.”

“Beastie?”

“A snake-thing. Ever so big. He saw it.”

“Where?”

“In the woods.”