You'll get the chance for this in the Sewer. There are 4 areas as far as I can tell where they appear:
1. Proceed through the level until you come to a puzzle where one character needs to open thick sliding doorways with levers on an upper level, and the other character is with the orb in a lower level, and ends up being penned in with a door to the SW, NW and NE directions. 1-2 worms spawn in this area - hard to miss these.
2. Later on there is a short hallway where you must roll the orb up to proceed. 1-2 worms fall from a pipe during this section - also hard to miss these.
3. Lastly, you'll come to a larger area with 2 large pipes in the middle of the area, and a LOT of worms spawn from the ground and fall from the ceiling, around 13-14% though the game progress which you can see when you hit
. Make your way methodically through this area and squish every worm that spawns in this area. This is where the achievement popped for me. If you proceed to the next puzzle with the circular revolving door and the achievement hasn't popped I'd reckon that you'd need to attempt it again.
4. Thanks to Christoph 5782 for pointing out, at 21% completion of the game, there are 4-5 more worms on the 2 pipes you have to walk the ball of light across immediately after completing the puzzle with the three revolving circular walls.