Di Long comes in two variants, Guang Di Long native to Guangdong, Guangxi, Fujian and collected from spring to autumn, and Tu Di Long collected during the summer in many regions of China. The abdomen of an earthworm of the ''L. rubellus'' species is cut open immediately after capture, whereupon viscera and extraneous matter are removed. The abdomen is washed clean, and dried in the sun or indoors at a low temperatures.
It is also used in the treatment of blepharoptosis, or drooping of the upper eye lid, along with other Phlegm Herbs .
According to TCM, Di Long is associated with the Bladder, Liver, Lung and Spleen meridians, and has Salty and Cold properties. It is thought to work by draining Liver Heat and by clearing Lung Heat, and also by clearing Heat in the collateral channels. Its "channel-opening" properties are thought to derive from its habits of burrowing through the earth, constantly searching out new spaces to slither.
Recommended dosage is 4.5 to 12 grams per day as an oral preparation.