Mud ding on a kind of look like sandworm and a little smaller than sandworm animals, mud ding, also known as mud worms or soil nails, mainly distributed in Zhanjiang City, Guangdong Province, and Beihai City, Guangxi and other coastal areas of the two sides. The whole year can be dug, especially to the Chung Yeung, autumn high season, individual larger, beach people in groups down the beach to dig used to do delicious ingredients, with the beach surface left a small insect holes, with a special triangular hoe, turn the surface of the soil to look for pinkish green soil with the worm channel, gently shallow digging, can be dug into the "soil nails". The price of live nails is about 35 yuan per catty (about 30-40).

Sandworms, also known as sea cucumbers, the scientific name of the square star worm, its shape is very much like an intestine, long cylindrical, body length of about 10-20 cm, and naked and hairless, the body wall longitudinal muscle into a bundle, each ring of muscle staggered arrangement, the formation of a square lattice pattern, the square star worm, although there is no sea cucumber, shark's fin, abalone's fame, but the taste of the fresh and crispy, sea cucumbers, shark's fins are not as good as. It grows in the coastal mudflat, because it is very sensitive to the quality of the growing environment, and once it is polluted, it can't survive, so it has the name of "environmental marking organisms".