CORRECTION: He was obviously Japanese, and meant to say "it'll
turn the cat into a walking flee killer!".  Ahem

    What Frontline (and other top spots) does is kill fleas after
they bite and if they don't die immediately, the secondary sterility
ingredients kick in.  These usually work by either preventing the
development of chitin (which young fleas need to have to break out of
their eggs) or by using an insect growth regulator that prevents
larvae and eggs from maturing.
    What a lot of people forget is that if you see fleas on your
pet, you've got fleas in your house.  And you've got hundreds of them
in your house, in the carpet, on pet beds, probably even in *your*
bed.  The species we call 'dog fleas' prefer to drink dog blood, will
drink cat blood, and don't like human blood.  The species called 'cat
fleas' will bite humans (and cats and dogs and pigs and civets and
just about anything else).  
    Female fleas lay 16-20 eggs per day -- around 600 in their
lifetime, and the population of fleas is generally 50% eggs, 30%
pupae, 15% larvae, and 5% biting adults.  You have to kill all the
fleas, not just the biting adults.
    To get rid of fleas you generally need a two step approach --
treat the pet and the environment.  Flea eggs are extremely tiny and
collect wherever a pet sleeps.  They hatch and turn into larvae, which
do not suck blood.  Larvae eat the pre-digested blood that makes up
flea dirt, and go into a cocoon.  They stay in the cocoon for five to
fourteen days.  At the end of that time they can emerge, or they can
stay in the cocoon for 2-3 months until they detect vibration,
pressure, heat, noise, or carbon dioxide (all of which signal a nearby
blood source).  You can get rid of fleas just using Frontline, but it
will take longer than treating the environment as well as using the
topspot.

Orchid
See Orchid's Kitties! -- http://nik.ascendancy.net/bengalpage
Want a Purebred Cat?  Read This! -- http://nik.ascendancy.net/orchid