perhaps Colorado potato beetle larvae.

See this
http://toxicfreenc.org/organicgardening/potato_beetles.html#.U37XHSgvCSo

Here is a link that might be useful: Colorado potato beetle

It's a slimy raisin bug. I get them too. Still have to look up the best line of defense, though, but for now I'm squishing them but more keep coming back.

https://c2.staticflickr.com/6/5147/5780953659_d0db3c65ba_z.jpg

Never seen those slimy creatures.
The only slimy things that I know and am dealing with are slugs and some snails.
Try using/ experimenting slug bait on those.
Also sprinkle some table salt on the and see what happens.

Sey