Studies On Cold Hardiness Of Prepupa And Life Table Of Laboratory Population Of Chrysopa Pallens (Rambur)

1. Cold hardiness of diapausing prepupa and non-diapausing prepupa of Chrysopa pallens (Rambur)In the laboratory, the cold hardiness ability of diapausing and non-diapausing prepupa of Ch. pallens was examined. The results showed that the diapausing prepupa of the lacewing was induced by the short-day photoperiods. In the condition of shorter photoperiod (L: D=9: 15), the supercooling point (SCP) (?13.31℃) and freezing point (FP) (?6.63℃) were lower than that in the condition of longer photoperiod (L: D=15: 9), (?9.61℃and ?3.98℃, respectively), and the differences were significant. Water content of diapausing pepupa was lower than non-diapausing prepupa (61.33% and 63.00%, respectively), the content of protein and soluble sugar in the body of diapausing prepupa were lower, too. But the fat content in the body of diapausing prepupa was higher than that in non-diapausing prepupa. The rates of respiration (Rr) and the rates of energy metabolism (Rm) of Ch. pallens with five different aggregation degrees were calculated. The five different aggregation degrees were represented by five different group sizes (1, 5, 10, 20 and 50 individuals). The results indicated that there were differences in the values of Rr and Rm among the five different aggregation levels. The values of Rr and Rm had negative correlation relationships with aggregation degrees. The Rr and Rm in the body of diapausing prepupa (132.53×10-3μL·g-1·s-1 and 32.47×10-4 W/g) were lower than that in non-diapausing prepupa (60.31×10-3μL·g-1·s-1 and 14.77×10-4 W/g).2. Seasonal changes in prepupa cold hardiness of Chrysopa pallens (Rambur)The weight, supercooling point (SCP), the content of water, fat, sugar and protein of prepupa of Ch. pallens natural population were detected from September 2009 to July 2010. The SCP and FP of Ch. pallens prepupa were lowest in January (?17.53℃and ?7.14℃, respectively) while hightest in July (?8.21℃and ?3.65℃, respectively). The pre-winter prepupa had lower SCP and FP than the summer and post-winter prepupa. Except for the content of fat, the variation tendency of all the other cold hardiness indexes first increased and then decreased. Changes of the fat content were contrary. The fat content of pre-winter prepupa (46.81%) was significantly higher than those in other seasons, in January to lowest (31.07%). The pre-winter prepupa had higher tolerance than the summer and post-winter prepupa. The cold tolerance of the prepupa varied obviously with seasons.3 The relationship between diapause and cold hardiness of prepupa of Chrysopa pallens (Rambur)The cold hardiness of diapausing / non-diapausing prepupa populations with a cold acclimation at 10℃and without cold acclimation ware determined. Under laboratory conditions, the SCP of non-diapausing prepupa with cold acclimation was ?12.18℃, while the SCP of diapausing population with short photoperiod induction was ?13.09℃. There was not significant difference between the two SCPs. The SCP of the diapausing prepupa with 10℃cold acclimation was ?14.97℃, showing a significant difference compared with that without acclimation. The SCP of prepupa under short photoperiod at 22℃was significantly lower than that of non-diapausing prepupa populations (?9.61℃). Short photoperiods and low temperatures maybe cause the prepupa weight, the water content, fat, protein and soluble sugar in the body to drop and the fat to increase.4 Age-stage, two-sex life table of Chrysopa pallens (Rambur)The life history of the green lacewing, Ch. pallens, was studied at 22°C, 15L ? 9D, RH 80% in the laboratory. The data of life history, such as development period, survival, mortality, fecundity and so on were recorded. The raw data were analyzed based on the age-stage, two-sex life table in order to take both sexes and the variable developmental rate among individuals and between sexes into consideration. All the eggs hatched successfully within 4-5 days, the preadult survival rate was 75%, 90.70% of adults emerged with 51.28% males and 48.72% females. The probability that a newborn egg survived to the adult stage was 0.38 for males and 0.35 for females. The mean longevity of male and female was 33.7 and 32.4 days, respectively. Maximum fecundity of each individual was 1289 eggs, maximum daily fecundity of each individual was 104 eggs, spawning peaked in the first 42 days.The intrinsic rate of increase (r), the finite rate of increase (λ), the net reproduction rate (R0) and the mean generation time (T) of Ch. pallens were 0.1258 d–1, 1.134 d–1, 241.42 offspring and 43.63 d, respectively. The life expectancy of a newborn egg was 48.85 days and the life expectancy of a newborn egg was 48.85 days. The maximum reproductive value of females was on the 37th day, which closed the total pre-oviposition period counted from birth (34.29 d). When the birth rate was 0.1396, survival rate was 0.9944 and death rate was 0.0056, the population of Ch. pallens was the most stable.