Possible larvae of the Limacodidae family. Larvae are typically very flattened, and instead of prolegs they have suckers. The thoracic legs are reduced, but always present and they locomote by rolling waves rather than walking with individual prolegs. They even use a lubricant, a kind of liquified silk, to locomote on.
Thanks to leads from LivanEscudero and Goody, more or less narrowed it down to the Limacodidae family. Would really like to know what this is.