Sciser-Xs crawl on the walls and will periodically fire energy balls from their claws. These balls fly out in an arc, but have a very short range. However, they can be dangerous in narrow passages or near doors and platforms. Scizers can be damaged by normal beam shots or Missiles. You can also charge up your beam and perform a charge spin attack to destroy them, which is very useful when they are guarding platforms. However, if enough X Parasites gather in an area with a Sciser, they will form a Gold Scizer, which is more difficult to destroy.
There is a large cluster of Sciser-X near the Level 4 security station. Use a Power Bomb to destroy them and quickly replenish your supplies.