Objective To investigate the role of ovarian development associated with environmental temperature in reproduction and population growth of Yunnan shoot borer Tomicus yunnanensis for further understanding the basic mechanism of its population fluctuation.

Method The females of T. yunnanensis were randomly obtained from the shoot of Pinus yunnanensis, and dissected on a paraffin plate.

Result The female reproductive system of Yunnan shoot borer is located in the inferior toward the lateral part of alimentary canal at the fourth abdominal segment. It consists of a pair of ovaries and two short lateral oviducts, a common oviduct, a spermatheca and two accessory glands. The ovaries have four tubular ovarioles. The terminal filaments extended from the anterior end of each ovariole can adhere to the internal tegument or fat body. According the morphological changes, the ovarian development was divided into five grades, including transparent period (grade Ⅰ), terminal elongation period (grade Ⅱ), previtellogenic (Ⅲ grade), vitellogenic eggs (grade Ⅵ), and ovipositing period (grade Ⅴ). Each grade of ovarian development can last less than 1 to 4 month, and show a closely relation to the nutrient acquisition. The length of ovariole grows slowly in the previous and middle and rapidly in late grades, but the width of ovariole grow rapidly in the previous and late grades. The whole size of ovary increase rapidly with a power-law dependence. Using Kendall's tau-b correlation analysis, it was found that the correlation between ovarian development and temperature was positive, and a negative relationship was found between oviposition and temperature.

Conclusion The ovarian devel-opment of female adults of T. yunnanensis focuses mainly on the middle and late grades. The environment temperature has a significant effect on the life style of shoot and stem, respectively. The results can help to further deepening the theoretical basis for the prediction of oviposition of Yunnan shoot borers.