The achievement requires you to open the eggs yourself with bombs (eggs that hatch on their own don't count).
- Go to Field K4
- Make sure your towers can't hit the queen (roll your mouse wheel down to reduce the range) or just use traps to protect your orb
- drop bombs on the eggs the queen drops being careful not to kill the queen
You can track your progress by clicking Stats on the map screen (look for "Monster eggs cracked") about 2/3 down the list with blue numbers.