The Ravenous Bugblatter Beast is so mind-bogglingly stupid that it thinks that if you can't see it, it can't see you. Therefore, the best defense against a Bugblatter Beast is to wrap a towel around your head.
Alas, my great aunt Susan was devoured by a Ravenous Bugblatter Beast of Traal. She did not have a towel handy. And they are very very ravenous beasts.