Fine structure and sensory apparatus of the mouthparts of the pear psyllid,Cacopsylla chinensis (Yang et Li) (Hemiptera: Psyllidae)

The pear psyllid, Cacopsylla chinensis (Yang et Li) (Hemiptera: Psyllidae), is one of the most significant economic pests of pear in China, causing direct damage through feeding by the highly specialized piercing–sucking mouthparts. The ultrastructural morphology and sensory apparatus of the mouthparts of the adult were examined using scanning and transmission electron microscopy. The piercing–sucking mouthparts of C. chinensis are composed of a three-segmented labium with a deep groove in the anterior side, a stylet fascicle consisting of two mandibular and two maxillary stylets, and a pyramid-shaped labrum. Proximal to the labium, the stylet fascicle forms a large loop within a membranous crumena. Mandibles, with more than ten teeth on the external convex region, can be seen on the distal extremity. Smooth maxillary stylets are interlocked to form a larger food canal and a smaller salivary canal. One dendritic canal housing 2 dendrites is also found in each mandible. Two types of sensilla trichodea, four types of sensilla basiconica, single as well as groups of sensilla campaniformia, and oval flattened sensilla occur in different locations on the labium, whereas a kind of sensilla basiconica is at the junction of the labrum and anteclypeus. Sensilla trichodea and sensilla campaniformia, always present with denticles, are present on the middle labial segment. Three types of sensilla basiconica, two types of sensilla trichodea and two oval flattened sensilla are located on the distal labial segment. The mouthpart morphology and abundance of sensilla located on the labium in C. chinensis are illustrated, along with a brief discussion of their taxonomic and putative functional significance.