If you control a creature that has more than one of the listed types (for example, Daggerfang Duo, which is a Rat Squirrel), it's only counted once for Swarmyard Massacre.
Create two 1/1 green Squirrel creature tokens. Then each creature that isn't an Insect, Rat, Spider, or Squirrel gets -1/-1 until end of turn for each creature you control that's an Insect, Rat, Spider, or Squirrel.
