Be nice to your worms: a study recently published in the journal BMC Ecology by scientists at the University of Natural Resources and Life Sciences Vienna shows how earthworms may reduce damage to plants from slug feeding.  

While imagining a nightly version of "Gladiator: Slugs vs. Worms" is intriguing, it seems that there is no direct interaction between the two slimy critters. Rather, the earthworms benefit plant health so that the plants themselves are able to fend off slug feeding with their own chemical warfare. The study also showed that greater plant diversity is the landscape was also a factor in protecting plants against slug attack.