Diapause Mechanism And Application Of Chrysoperla Sinica(Tjeder)

The lacewing, Chrysoperla sinica (Tjeder) was known as an important natural enemy attacking agriculture and forestry pests like aphids, mites and eggs, young larvae of lepidopterous insects, and a good biological control agent. This species overwintered as adults, but only a few studies had been done to investigate the termination of adult diapause. This paper mainly dealt in details with the ecological, physiological and biochemical mechanism of adult diapause in natural and experimental conditions. Egg forecasting in the field by the method of developmental grading of female reproductive system and larvae searching behavior were also preliminarily studied. The main results were summarized as follows.1. Population fluctuations of Chrysoperla sinica and Effects of Ecologic-al Factors on the Survival Rate of Overwintering AdultsIn Tanshan district of Tai-an, the phenomenon of C. sinica generation overlapping was obvious in the field; this species overwintered as diapausing adults in nature. The adult population was rare in spring, and remained low until the end of May. Four adult peaks occurred from June to September in the agricultural fields, orchard, and mountainous region, especially the adult peaks in orchard in June and in nursery garden of Euonymus joponicus in September were much distinct. In the plain area, overwintering C. sinica adults were found in the nursery garden, woods and leaves in orchard around agricultural fields. In hilly region, overwintering adults were found in the south- and east-facing low clumps of shrub and the crowns of pine and cypress.The survival rate of overwintering C. sinica adults in their natural overwintering site was much low, only about 10%~20%, the major ecological factors affecting survive of overwintering adults were temperature, relative humidity and food. The survival rate of adults hi natural overwintering site could be enhanced by the methods of collecting and storing them in the relative airtight implements and providing them sufficient foods before and after overwintering. Studies on the effects of temperature and relative humidity (RH) on the survive of overwintering adults collected from outdoor hi laboratory showed that 5*C ~ 9"C and RH 70% ~ 85% were the favorable storing conditions, under above conditions, the survival rate of overwintering adults was above 50% after five months storage. Temperature below 5 癈 and RH lower than 70% or higher than 90% could reduce the survival rate.2. Ecological Mechanism of Adult diapause of Chrysoperla sinicaThe studies indoor and outdoor showed that the C. sinica exhibited a facultative adult diapause induced under a short-day photoperiod, diapause was induced and terminated reversibly by photoperiodic changes between short-day (diapause-inducing) and long-day (diapause-preventing) conditions. In field, The overwintering population consisted mainly of adults of the fourth generation and of a small amount of the third and fifth generation. The photoperiodic sensitive stage was adult,and short-day experience of the third instar larvae, prepupa, pupa could promote the induction for adult diapause . At 15 "C ,20 癈 ,25 癈 ,and 27 癈 ,the critical daylenths for the induction of diapause were between 13hr and 14hr,12.5hr and 13hr , 12hr and 12.5hr ,llhr and 12hr, respectively . The primary factors affecting the adult diapause were photoperiod and temperature, and the key factor was photoperiod .Photoperiodic sensitivity persisted throughout the adult life. The diapausing adults showed clearly a quantitative photoperiodic response that different photoperiod have thus different quantitative effects on both the initial intensity of diapause and the rate of diapause development, and a recurrent photoeriodic response that adults could resume response to the diapause-promoting photoperiod after they terminated diapause and had a short period of oviposition. In post-diapause, diapausing adults lost sensitivity to photoperiod.Temperature wasn't the key factor controlling the adult diapause of C. sinica, but...