Have you applied any bug boundary or something similar? Hissers are climbing roaches, they can climb right up the glass if you don't put down a barrier to stop them.

This is the first product I can think off offhand, but I know there are other methods out there (one of which is vaseline, and if you're using these as feeders, I don't recommend that).

http://www.blaberus.com/FORMgallery5.htm