Ants are terrestrial, so only terrestrial/semi-aquatic crustaceans have any chance of showing up. The only option beside hermit crabs and woodlice are land crabs. The 4th set of missions set in a North Carolina swamp, so it's not like there is no chance.
Also, they don't give spoiler outside of Screenshot Saturday/ Newsletter. The whip spiders revelation proved this to be effective in creating excitement.