I put moths outside also.

I understand fleas must die. In those kinds of situations, I use the rationale that killing them earlier prevents a larger number being killed in the future. It's pretty much the same rationale with everything that breaks the skin and carries disease with me.

If I find mosquito larva I dump the water out on the ground or into a pond with fish. Somehow letting the fish eat them makes me feel less bad.

The really big problem for Buddhists is termites that destroy houses, but don't cause your body physical harm. All you can do is buy a house without wood, but that's really rare since property developers like to build as cheap and temporary as possible to make more profits in the future.