Just because you can't see them does not mean that they aren't there.

Many host plants hide their host very well, or should that be that many host hide well in their host plants.

Well, one of my Cassia trees has reached a large size. I have always seen evidence of insects having munched away at the leaves year after year without ever finding a cat.

This year I guess it has reached a more acceptable size to gravid giant sulphurs because I have frequently seen them laying eggs on it.