Freshwater crab alias: Eriocheir sinensis is mainly distributed in tropical areas and extends to subtropical and temperate marginal areas. There are more than 200 species and subspecies of freshwater crabs in Palaearctic, Japan and Oceania. Except for a few areas (Xinjiang, Qinghai, Inner Mongolia and Northeast China), China is almost distributed in all provinces and regions of the country, with an estimated 100 species. Most of them live under rocks in mountain streams or between aquatic plants and sediment on both sides of streams, and some also live in caves on the banks of rivers, lakes and ditches. They don't soak in water for a long time, but live a semi-terrestrial life at the water's edge or in wet places. Omnivorous, but prefer meat, mainly feeding on fish, shrimp, insects, snails and dead and rotting animal carcasses. Sometimes they eat the same kind, especially the soft-shelled crabs that have just been shelled. The breeding season of crabs is from April to September, which varies from region to region. Males and females can mate in the hard shell and fertilize in the body. Due to the adaptation to semi-terrestrial life, the fertilized eggs discharged by crabs have thicker eggshells. Female crabs lay about 50 ~ 300 eggs at a time. Eggs are firmly attached to the bristles of the inner limbs of abdominal limbs, and the hatched larvae are basically similar to adults. They are too thin to live independently. But attached to the mother's abdominal limbs, and began to live independently after 2 ~ 3 weeks without any abnormal condition. Many areas in China often prey on crabs, which can be drunk, pickled, fried or eaten raw. Eriocheir sinensis is the main second intermediate host of human paragonimiasis and should not be eaten raw. Eriocheir sinensis originated from Cenozoic tertiary. At first, taxonomists divided crabs into two families, Plumbagae and potamidae. Now it has been divided into the above three general families.