Humidity
Upon your regular inspection, you may find that the moisture level of the culture has dropped and that the surface of the soil has begun to dry out. If this condition is allowed to continue the worms will start to go deeper in the soil seeking moisture. When they do this, they are also moving away from the food you place on the surface of the soil.
To counteract this problem, spray the surface of the soil with water to maintain a damp, but not soggy, look and feel. A plant sprayer or mister can be used for this purpose. The regulation of moisture may be aided by removing the cover for a time as necessary to allow for evaporation.
Read more about this topic: Enchytraeus Buchholzi