A Worm.
Worms appear as regular enemies in All Kamen Rider: Rider Generation and it's sequel, All Kamen Rider: Rider Generation 2. They originally appeared in Kamen Rider Kabuto. Worms come in three colors, the original green, white and black. White Worms are stronger then the normal Green Worms with the Black Worms being the strongest out of the Worms.