Any idea of why they continue to flourish, an more importantly, how to rid
my kitchen of this scourge?

I'd say they are UNDER the D/W. Try taking the lower panel off and putting
a sticky pad insect catcher under there. If they are, use AMDRO (sp).
Its a type of bait they take back to the anthill thats supposed to "kill em
all".

It would be a good idea to try and find where they are getting into the
house from outside and doing some serious caulking/sealing too

R