The microstructure of the digestive and excretory systems of the adult female mealybug, Phenacoccus fraxinus Tang (Hemiptera: Coccoidea: Pseudococcidae), was examined using light and scanning electron microscopy. Results revealed that the digestive system consisted of a distinct foregut, midgut and hindgut. The foregut is short, membranous and subdivided into a pharynx and an esophagus. A pair of salivary glands, well-developed and racemous in appearance, are situated on both sides of the pharynx. The midgut is elongated and loop-shaped with epithelial tissues protruded into the enteric cavity. The gastric caeca are blind lateral diverticulum of the midgut. The hindgut possesses an enlarged enteric cavity with small epithelial cells. The filter chamber is well-developed, but the epithelia are reduced in size. The surface of the gut is innervated with tracheoles, nerve fibers and fat body. The Malpighian tubules, numbering two, are brownish-yellow, moniliform, with the interior appearing faviform in structure.