2. Spider is the most abundant predatory natural enemy in terrestrial ecosystem, and its role in maintaining the stability of agroforestry ecosystem can not be ignored. Body length 1 ~ 90 mm, the body is divided into chest (front) and abdomen (back), and the head and chest are covered with carapace and chest plate. There are two pairs of appendages in the head and chest. The first pair is pliers, with a forceps tooth and a poisonous gland opening at the tip of the forceps tooth. The pincers in the orthopalatine suborder move back and forth, and the pincers move laterally in the opposite direction; The second pair is whisker limbs, which are in the form of feet in female spiders and immature male spiders, and are used to hold food and act as sensory organs; However, in male adult spiders, the terminal part of the whisker limb will swell and become the interface for transporting sperm.