Roaches spawn in caves. They are small and afraid of the player and spiders. They love bread and can be bred with it.
Moths spawn in caves. They fly around and have a brown spotted pattern on their wings, similar to the common brown house moth.
Flies spawn near animals and zombies. They fly around. That's it.
Snails spawn in birch forests and flower forests. They are slow, slimy, and can be bred with leaves. When killed they drop slimeballs.
This mod requires Geckolib