I just used lemon extract on mine and it worked wonders.
Someone else told me to kalk bomb them..aka make a little paste like ball and drop it into their 'mouth' and let them pull it into their hiding place with them. Essentially poisoning them...

I read from someone else somewhere that you can get em with a bit of vinegar into their "stock". I have done this with 3 so far by injecting with a small needed into their base and hitting em with just a tiny amount. None came back...