| The lacewing, Chrysoperla sinica (Tjeder), is an important natural enemy attackingagricultural and forestry pests, such as aphids, mites and eggs, young larvae oflepidopterous insects. This species overwinter as diapausing adults. Using natural adultsas material collected from Taian (36o16'N, 117o6'E), Shandong, China, this paperinvestigated the cold hardiness and overwintering ability; The effects of photoperiod andtemperature on adults'diapause and cold hardiness were also studied. Using experimentaladults as material, this paper mainly dealt with the relationship between diapause and coldhardiness of Chrysoperla sinica (Tjeder). The main results were summarized as follows.1. Cold hardiness and overwintering ability of diapausing adults of chrysoperlasinica in natureThe supercooling ability of adults at different times was investigated. The resultsindicated that the supercooling ability increased with time at the beginning ofoverwintering. In January the females'supercooling point (SCP) was lowest, which was–15.69℃, and females'freezing point (FP) had the lowest value in December, which was–9.60℃. The males have the strongest supercooling ability in December, SCP and FPwere –17.04℃and –11.75℃, respectively. At the end of overwintering the adults'supercooling ability decreased, which meaned that the adults are terminating diapausegradually.Diapausing adults gradually eliminating free water in body at the beginning ofoverwintering. In February free water content was lowest, the content of famale and malewas 48.05% and 46.79%, respectively. When terminating diapsause the free water contentincreased with time. By comparing the supercooling ability and free water content, itcould be found that there was a strong correlations between them(y=-27.253+0.2529x,R2 = 0.3193, y: SCP, x: free water content, n=124)Diapausing adults accumulated much fat in body for overwintering, and the fat contentexceeded 45% both in females and males. During overwintering fat was consumedgradually. In February the fat content of famales and males decreased to 34.4% and 26.0%, respectively. At the end of overwintering the fat content increased mainly becausethe adults were supplied much nutrition.When stored them in the relatively airtight containers and providde them with sufficientfood during overwintering, the survival rates of adults in natural overwintering site couldbe enhanced. Up to the middle of February, the survival rates of male and female stillremained 89.9% and 81.2%, respectively. After the middle of March, the survival ratedecreased steeply, on April 30 the survival rates of female and male were 41.9% and 5.4%,and the survival rate of female was significantly higher than that of male.2. The effect of photoperiod and temperature on overwintering adults'diapauseand cold hardiness At the end of overwintering the adults lost photoperiodic sensitivity, even thoughphotoperiod had effect on oviposition. That is to say, post-diapausing adults could notresume response to the diapause-promoting photoperiod after they terminated diapause. Under the short photoperiod and the temperature higher (25℃) or lower (10℃) thanthe developmental zero (12.6℃), or under the long photoperiod and 25℃, overwinteringadults'cold hardiness and free water content both increased. Under the short photoperiod, lower temperature (10℃) was more favorable for adults'survival than higher temperature (20℃). At 20℃adults could terminate diapausegradually and then they would have bigger reproductive potential. While at 10℃adultskept diapause body color on the whole, even though a few adults oviposited, laying timewas late and the number of eggs was little. Overwintering adults'SCP and FP changed like the letter "M"when diapause wasbroke. And the breaking time had remarkable effect on the reproduction. The breakingtime earlier, females'fecundity stronger. When diapause was broken in January, Februaryand March, the ovipositing number of 10 females was 1537, 423 and 18, and the hatchingrate was 96.3%, 88.1% and 74.2%, respectively.3. The relationship between diapause and cold hardiness of Chrysoperla sinica Under laboratory conditions, The SCP of non-diapause adults without cold acclimationwas –12.98℃. Diapause and cold acclimation both could enhance adults'cold hardiness.Diapause without acclimation made SCP decrease by –15.54℃, and cold acclimating ofnon-diapause adults also led SCP to –15.66℃. Further study indicated cold acclimating ofdiapause adults made SCP decrease by–15.95℃. This suggests that non-diapause adultshave the same cold acclimating potential as diapause adults. We can also find that underlaboratory conditions diapause or cold acclimation can not make the SCP decrease to theSCP level of overwintering adults in the fields, for some overwintering diapause adultshad SCP lower than -20℃. Why this phenomenon was made was discussed. Diapausing adults experienced a natural process before overwintering. At late autumnand early winter photoperiod are shortening gradually in the nature, often occompanyingwith the decrease of temperature. From this sense,it can be concluded that shortphotoperiods and low temperatures probably have common effect on increase of coldhardiness for Chrysoperla sinica. The effect of diapause on free water and fat in body differ from that of cold acclimation.Former investigation suggested the key factor affecting the adult diapause of Chrysoperla...
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