The Chinese pine caterpillar Dendrolimus tabulaeformis is an important destructive leaf borer in boreal coniferous forests in China. This species overwinters in the larval stage. Changes in supercooling capacity and physiological-biochemical parameters of D. tabulaeformis larvae from a natural population were evaluated at different stages during the overwintering period. Cold hardiness of overwintering larvae collected in January was significantly greater than that of larvae collected in other months. January larvae survived for 15 days at -10°C and for approximately 2 days at -15°C. By contrast, larvae collected in September survived for no more than 4 h at -5°C and those in November and March no more than 1 day at -15°C. Supercooling point gradually decreased from -5.9 ± 0.3°C in September to a minimum of -14.1 ± 1.0°C in November, then gradually increased to the original value with the advent of spring. Water content gradually decreased from September to November, remained at approximately 74.5% until March and then gradually increased to levels similar to those in September. The lipid content gradually decreased from September to November, remained stable at approximately 3.2% until March and then gradually increased to levels similar to those in September. Glycogen content increased to a peak in November and then decreased. The concentrations of several metabolites showed significant seasonal changes. The most prominent metabolite was trehalose with a seasonal maximum in November. Glucose levels were highest in January and then gradually decreased until in May they were at levels similar to those in September. Glycerol levels remained relatively stable during winter but increased significantly in May. This study indicates that D. tabulaeformis is a freeze-avoidant insect. Larvae increase their supercooling capacity by regulating physiological-biochemical parameters during overwintering., Yuying Shao, Yuqian Feng, Bin Tian, Tao Wang, Yinghao He, Shixiang Zong., and Obsahuje bibliografii
Larvae of Dendrolimus punctatus overwinter in diapause. In the Yangtze River Region, this species is multivoltine at altitudes below 400 m and univoltine above 700 m a.s.l. The photoperiodic response of the univoltine population, investigated at five day lengths (11.5, 12.5, 13.5, 14.5 and 15.5 h) at 27 + 1C, indicates that D. punctatus is a long-day species. Diapause was induced in 95-100% of the individuals by three short photophases (11.5-13.5 h), while diapause incidence decreased steeply with increase in day length down to 10% at 15.5 h. The critical daylength (CDL = day length resulting in a 50% incidence of diapause) is 14.6 h. When induced by critical or longer photophases (14.5 and 15.5 h), diapause terminated spontaneously, without any change in photoperiod or temperature. Diapause induced at shorter photophases was more intense and not terminated without activation by diapause averting conditions. Larvae in diapause lived for up to 190 d when kept under a 11.5 h photophase during which they remained sensitive to the photoperiodic signal. In transfer experiments, diapause was terminated after an increase in photoperiod, even if it was within the range of diapause inducing photoperiods: from 11.5 h to 13.5 h. This study revealed that the univoltine hill dwelling population of D. punctatus undergoes a facultative diapause. Although potentially multivoltine they are univoltine because of the low temperatures at that altitude., Ju-Ping Zeng, Yong Wang, Xing-Ping Liu., and Obsahuje seznam literatury