Taxonomy and biology of pear psyllids with color polymorphism in the pear orchards of central Taiwan

• Main Authors: Ji-Hong Huang, 黃智弘
• Other Authors: Man-Miao Yang
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/34030221251030129013

碩士 === 國立中興大學 === 昆蟲學系 === 92 === Psyllids belong to the superfamily Psylloidea (Hemiptera) and there are about 2,500 recorded species worldwide. Pear psyllids are a group of psyllids that infest pear trees and belong to the genus Cacopsylla (Psyllidae: Psyllinae). More than 28 psyllid species infest cultivated pear trees in temperate and subtropical regions of the world. Not until a decade ago, a first Cacopsylla species, Cacopsylla qianli (Yang & Li), was found in 1994 in pear orchards of central Taiwan. Later on, another group of pear psyllids with varied body colors and unknown biology outbroke in 2002. The major goal of the present study is to clarify the taxonomic status of the later discovered pear psyllids with varied body-color, and to establish their biological information. After a thorough examination of both adult and nymphal morphology, and a comparison with type material, these pear psyllids are identified as the same species as C. chinensis (Yang & Li), which was formerly described only from northern China. C. chinensis has seasonal dimorphism, the summer form and the winter form. The summer form of C. chinensis exhibits a variation in body color from light green to light yellow, while the winter form with body colors of dark brown. Fifth instar nymphs of C. chinensis has many long simple setae on the body surface, and female individuals have a Y-shape suture in front of circumanal pore ring, which is absent in male. Field investigation showed that the major occurent peaks of adults of C. chinensis were in July, while the peaks of nymphs and eggs were in August and July, respectively. The population size of C. chinensis in Taiwan increased rapidly in April, it is suggested that management should take place in March or April before the raises of population density. Laboratory studies showed that it took about 50~70 days for C. chinensis to complete its life cycle. The length of life cycle of the winter form was longer than that of the summer form, and the life cycle was lengthened under low temperature treatments. Regardless of different temperature treatments, the light-color individuals of summer form were obtained under long photoperiod conditions, while the short photoperiod treatments produced dark-color individuals of winter form. The results suggest that the length of photoperiod is an important environmental factor affecting the seasonal dimorphism of C. chinensis.