A year later: All crustaceans on earth have been killed. The invaders, living in their own "bubble", don't even look anywhere but under water and don't recogni

A year later: All crustaceans on earth have been killed. The invaders, living in their own "bubble", don't even look anywhere but under water and don't recognize land based life forms or land based anything, and since they themselves are crustaceans they don't think any other species could ever be a threat. Again we survived another alien attack thanks to living organisms brains limited abilities of perception. The last serious invasion killed off all silicon based life forms two billion years ago by an intelligent rock species.