Fun game! Took me a few goes but eventually beat Year 5 with the last crab, it was a good test of skill. The sprites and music is really nice - I liked the count in at the start of each level/year.
I think if you had disabled the collision on the ants a bit sooner (like when the death animation plays) the game would have been a little easier. A few times I clicked on an ant that had reached the path and it managed to take a few crabs down with it during its death animation - although maybe we could just say that was the acid left behind by the dead ant, haha. Nice work though.