Responses Of Chrysoperla Sinica (Tjeder) Under Long And Short Photoperiods

The green lacewing, Chrysoperla sinica (Tjeder)(Neuroptera:chrysopidae) is an important natural enemy attacking many agricultural and forest insect pests and mites, and while known as a good biological agents. As polyvoltine insect, the facultative diapause overwintering stage is the adult of4th or5th generation. Photoperiod plays an important role in the green lacewing cycle life. The virgin adults quickly mated and oviposited under long photoperiod (15L:9D), but entered diapause under short photoperiod (9L:15D). Changing the short photoperiods to long-day ones, the diapause adult can terminate diapause and restore reproduction. The purpose of our research was to detect the response of the green lacewing to long and short photoperiods from different aspects. We made the studies on the ecological, physiolodical and biochemical indexes of individuals under long and short photoperiods, and population biology of the green lacewings under two photoperiods. The major results were summarized as follows.1. The overwintering green lacewing could terminate diapause in both long and short photoperiods, with different physiological and biochemical responses during diapause termination. The results showed that the dry weights of female adults under the long photoperiod were heavier than those under the short photoperiod, but contrary to male adults. The water content of the female and male adults showed an upward tendency under both photoperiods and increased significantly under long photoperiod. The protein content of the female adults treated for15d and the male adults treated for10d under short photoperiod were significantly lower those under long photoperiod. The glycogen content of the male and female adults under long photoperiod was significantly lower than those under short photoperiod. The biochemical compounds analysis in the newly ovipositing adults under different photoperiods showed that the protein and glycogen contents in female and male adults under long photoperiod were significantly lower than those under short photoperiod, while the water content in male adults was significantly higher than that in female adults. The results indicate that (1) the reproductive system can be inhibited by short photoperiod to some extent;(2) biochemical content was different when diapause termination under long and short photoperiods;(3) the reproductive system can development slowly under short photoperiod, and the diapause termination caused by the quantitative to qualitative change.2. The adults of Ch. sinica aggregate significantly during overwintering. The rates of respiration and the rates of energy metabolism lowered as the aggregation degrees were increased, that is the adaptation strategy of the green lacewing under long term natural evolution. The rates of respiration and the rates of energy metabolism showed an upward tendency and increased significantly under short photoperiod, while showed a drop tendency after the pink15d under the long photoperiod. The energy metabolism rates in the diapause termination adults under short photoperiods showed lower than that long photoperiod. The results indicate that diapause termination under short photoperiod needs more energy cost than under long photoperiod.3. The Super colding point (SCP) values of overwintering Ch. sinica adults in December were mainly distributed between-10℃and-14℃. The SCP values of43.70%overwintering adults were below-12℃, and the mortality of overwintering adults at-12℃for1d was62.00%. The mortalities of overwintering adults at-12℃treated under the long photoperiod were higher than those under the short photoperiod. The mortalities of the2nd and3rd instar larvae at-7℃under the short photoperiod significantly lower than those under the long photoperiod. The results indicate that the Ch. sinica is a freeze-intolerant insect, and its cold hardiness could be enhanced under the diapause-inducing short photoperiod.4. Activity changes of four enzymes in naturally overwintering adults of Ch. sinica were complicated. The catalase (CAT) activity of both female and male adults reached a peak at5d after treatment and was higher in long photoperiod than in short photoperiod. However, the CAT activity was significantly lower in long photoperiod than in short photoperiod at10d after treatment. The superoxide diamutase (SOD) activity of male adults under long photoperiod was higher than that in short photoperiod, while the Na+K+-ATP activity was opposite. The lactic dehydrogenase (LDH) activity decreased with the time under the two photoperiods, and the activities in both treatments. The results indicated that the differences of enzyme activities of Ch. sinica under the long and short photoperiods may be the main physiological factor triggering the content of bio-chemical substances in the adult body and reproductive status during the adult diapause termination.5. The research on population biology show out that the developmental time of the larval and total preadult stages of the lacewing reared under the short photoperiod were longer than those under the long photoperiod, while the fecundity under the long photoperiod was higher than that under the short photoperiod. The survival rate of Ch. sinica at every age was lower in the long photoperiod than in the short photoperiod, while longevity expectancy in the short photoperiod was longer than that in the long photoperiod. The shorter developmental time and higher fecundity at long photoperiod consequently result in higher intrinsic rate (r), net reproductive rate (R0) and gross reproduction rate (GRR), and shorter mean generation time (7) in comparison with those at short photoperiod. There were more females than males (female: male=1.88:1) at long photoperiod in contrast to the sex ratio1:1.81at short photoperiod. The larva age distribution was larger in the long photoperiod than in the short photoperiod and the adult age distribution was shorter. Our results demonstrate that demographic analyses offer a comprehensive understanding of the response of Ch. sinica to photoperiod.6. Diapause experience and photoperiod could affect post diapause biology and the offspring development of Ch. sinica. The post-diapause development of Ch. sinica adults showed that:the overvintering periods had significant effects on pre-oviposition period and fecundity, this indicates that the green lacewing has different diapause intensities in different months and would influence the fecundity because of the energy consumption during the process of diapause termination. The photoperiod had no significant effects on the pre-oviposition period, oviposition periods and female longevity, but significant effects on fecundity. The parameters of the offspring population showed that there were significant differences between the offspring of the November population and the June population, whereas the parameters of the population in the March were closely to that in the June. The production and reproduction development were the highest in March, lowest in the November. However, the life expectancy was the highest in the June with120.03d, lower in the March with82.62d under the short photoperiods, while the life expectancy of the other treatments were between58～68d, and lowest in March with58.61d under the long photoperiod. The reaults indicated the diapause experiences of Ch. sinica can affect the developmental characters of their offspring.