Don't buy expensive chemicals, that are dangerous to not only the beasts. It is very easy and readily available.
1/2 cup od sugar
1 1/2 tablespoon Borax
1 1/2 cup of hot water
Mix all well until you have a nice syrup, then put on cotton balls and place strategically. Toilet paper works also wonders :).
Good luck with your new weapon of mass destruction :)