Twinmold

Twinmold is a pair of humongous insects found in the fourth area (Stone Tower Temple) in The Legend of Zelda: Majora's Mask. Twinmold is defeated by hitting its head and tail. This can be done as normal link by Z-Targeting it and using arrows, bombs, or sword. Alternately Twinmold can also be defeated by using the Giant's Mask and sword to even out the size difference, because your chances of getting a hit improve while wearing the Giant's mask, Z-Targeting is disabled. Using the Giant's Mask also greatly drains your magical energy. If you plan on wearing the Giant's Mask make sure that you have a lot of potions with you, or a better approch would be to drink a bottle of Chateau Romani before the battle which will suspend the consumption Link's Magic Meter. After defeating Twinmold your reward is one full Heart Container and Twinmold's Remains.

Twinmold is probably a species of Moldorm, as it resembles the Moldorm in terms of weakspots. However, it is more like the Lanmola in terms of strategy, and so may actually be a link between the two.