I found the most unusual critter and have been trying for a very long time to find someone who could tell me what it is. Now, thanks to Riaan, I eventually know what it is.
This is a very small creature, about 3-4mm in length."The larvae of leaf beetles (Chrysomelidae) are very diverse, mostly varying along with their taxonomic diversity. Some live inside plant material (e.g. subfamily Bruchinae in seeds and tribe Hispini as leaf miners), but most feed externally on their host plant (above ground on any possible plant structure, even dead material in some instances, or underground on roots). Some chrysomelid larvae are case-bearers.
The larva in this observation seems typical of several leaf beetle groups that feed externally on leaves. The body is slug-like, shiny, sometimes slimy, but typically crinkly, and there is a well-sclerotised (hardened) head capsule with powerful mandibles. And they always have three pairs of thoracic legs.
Thank you Riaan from http://www.ispot.org.za for the identification and the interesting information. It is greatly appreciated.