Also Known As Vermillus
From Ultimate Ghosts 'n Goblins

Vermirous (ヴァーミラス Vāmirasu) is the keeper of the Third Demon Gate in Ultimate Ghosts 'n Goblins, a giant flea covered in a thick layer of rotten flesh. It usually moves slowly, but once it spots a victim, it moves in for the kill with surprising speed and agility. It also releases Free Fly (フリーフライ) parasites to help capture its prey.

Later, Arthur may fight Vermirous or Spiral Mantruder again in the Black Palace.