The first butterfly can be found on the wall around half way through the level.
Climb the ladder on the wall and beat the firebreather. The butterfly is against the far wall behind him.
The second is in the second half, in the section blocked by Moneybags.
Head past the door and through the level until the three tall ladders. Climb the ladders and follow the path round. Before the hole that leads to Hunter's underwater area, the butterfly is on the ledge opposite.