Bats, a collective term for mammals in the order Pterodactyla, are mammals with the ability to fly. The forelimbs of bats are extremely slender except for the first finger, with thin and hairless wing membranes between the fingers and between the forelimbs and hind limbs, and usually also between the hind limbs; Bats are divided into two categories, big bats and small bats. The name Pterodactyls is derived from the characteristic of their forelimbs or hands degenerating into wings. Beneficial to humans due to the large predation of insects, it plays an important role in agricultural and forestry ecosystems, and the feces in caves are excellent phosphate fertilizers. Some bats are also carriers or hosts of pathogens, which can pose a threat to fruit trees.