Abstract: The histology of alimentary canal of Simulium （Wilhelmia） xingyiense mature larva （with gill spots） was investigated by using paraffin serial section. The alimentary canal is composed of foregut， midgut and hindgut. The foregut includes pharynx， esophagus and proventriculus. The up-inside of buccal cavity invaginates to form the labral gland with irregular shape. Ossified cibarium exist in anterior pharynx. Canular proventriculus forms by the invagination of esophagus. The midgut begins with four big gastric caeca， and divides into three regions according to the epithelium cell shape. The hindgut consists of pylorus， ileum and rectal. The structure of the ileum is different from rectal. Four malpighian tubules diverge from the boundary between midgut and hindgut. The structure of silk duct is special.

Key words: Simulium （Wilhelmia） xingyiense, Larva, Alimentary canal, Histology