Make a swimming pool for fleas
Try this recipe for catching the fleas attacking your cat: use a shallow pan half filled with soapy water (use Ivory Liquid soap). Place a light over the pan to attract the fleas. The fleas like the heat from the lamp and jump for the heat, fall into the water and lack swimming skills, so they drown. The soap eliminates the surface tension of the water and the fleas can’t bounce back.
From: The Buggy Professor’s Club the Bugs & Scare the Critters: Dr. Myles H. Bader.