Yes, placing a light over a shallow bowl of water at night is a good way to
catch fleas.  The warm moisture attracts them, they jump in the bowl, and
can't get out.
 
This is a good non-toxic way to deal with the fleas that may be lurking in
your carpet after treating your pets.  I have used it successfully after a
severe infestation, catching about a dozen fleas the first night, and fewer
each succeeding night until they were gone.
 
This does NOT work if your ferrets free roam at night. :-)
 
Linda Iroff
Oberlin OH
[Posted in FML issue 2999]