You have no hope, resistance is futile....they are the Borg.
Seriously, the drops work for me, as mentioned here already, though it helps to figure out what they're after so you get the right stuff. Failing that, get the flashlight and find out
where the little bastards are coming in, and seal it up. Lastly, call the exterminator, see if you can get the landlord to pay for it.
Good luck.
JC