Biological Characteristic Of Chrysopa Formosa Brauer And It’s Predation Efficiency On Dysmicoccus Neobrevipes(Beardsley)

The biological characteristic of Chrysopa formosa Brauer was studied under room temperature and five constant temperatures (24℃、26℃、28℃、30℃and32℃). It’s predation efficiency on Dysmicoccus Neobrevipes (Beardsley) and C. formosa preferences for preys were also studied in this paper. The main results were as follows:1. Morphology and habits of C. formosaC.formosa was a local natural enemy of D. neobrevipes. Adults was green, with metallic luster compound eyes. Membranous wing was transparent, and had the reticulate venation. Eggs had long silk handle. Campodeiform larvae were able to prey. Pupae was exarate pupae. Larvae of C. Formosa prefered to feed on1st instar nymphs. The habits of C. formosa, which including hatching, molting, pupating, emergence, mating, oviposition, predation and so on were observed. C.formosa was a kind of complete metamorphosis insect, and it was consisted of four stages which is egg, larva, pupa and adult. The larva was comprised of three instars. From the observation, the larva was good at camouflage, and it liked carrying prey fragments and food debris after feeding. Under harsh environments such as the shortage of food, C. Formosa tended to kill each other. The adults had the habits of phototaxis and liked to moving up. The oviposition was selectivity.2. The development, lifespan, fecundity and the day predation of C. formosa at room temperatureThe development of each stage at room temperature were as follows:egg was4.50days,1st larva was5.81days,2nd larva was5.20days,3rd larva was6.12days, pupa was14.61days, pre-oviposition was7.63days, one life cycle was43.70days. The average longevities of females and males were41.67and13.00days, respectively. Averagely,11eggs were laid by a C. formosa female in a day, and a female laid110eggs averagely for her life.1st instar nymphs of D. neobrevipes prey about2201st instar larvae of C. formosa (daily28); f2nd instar larvae of C. formosa prey5261st instar larvae of C. formosa (daily106);3rd instar larvae of C. formosa prey11861st instar larvae of C.formosa (daily170);1st instar larvae of C. formosa prey592nd instar nymphs of D. neobrevipes (daily8);1st instar larvae of C. formosa prey263rd instar nymphs of D. neobrevipes (daily4). C.formosa can not complete generation when prey on3rd instar nymphs of D. neobrevipes, or the cocoons were smaller than normal ones.3. The influence of temperature on the development and survival of C.formosa (1) The development of C. formosa:under the temperature of24℃-32℃, it could complete generation development, and the developmental period of all stages and life cycle of adult shortened with increasing temperatures. The development was the fastest at32℃, at which the development period of each stage were as follows:egg was3.20days,1st larva was4.09days,2nd larva was4.45days,3rd larva was4.23days, pupa was10.94days, pre-oviposition was5.89days, one life cycle was32.17days.(2) The survival rate of C. formosa:The temperature had a great effect on the survival rate of C. formosa, especially low temperature. The lowest survival rate was at24℃. With temperature range of24-28℃， the survival rate increased with temperature, and the survival rate of declined with temperature range of28-32℃. According to the survival rate, the order of temperature was28℃>30℃>26℃>32℃>24℃.(3) The developmental threshold temperature and effective accumulated temperature: Under the constant temperature, the threshold temperature of egg, larva, pupa, pre-oviposition and egg-adult is9.22℃,7.47℃,8.69℃,7.04℃,6.72℃respectively, and their effective accumulated temperature is72.40,302.21,240.86,140.49,793.16respectively. It occurred8generations in Haikou which was the north of Hainan island and9generations in Sanya city which was the southern of Hainan island.4. The predation efficiency of C. formosa on D. NeobrevipesAll the larvae stages of C. Formosa showed a Type Ⅱ functional response. Based on the random predator equation, estimated maximum of pseudococcidae predated by one larva during24hours period were91.0412,191.1940,265.3587and the parameters of functional reaction a’/Th ere85.4367,125.5375,200.4754for the1st,2nd and3rd instars, respectively. Mutual interference among the2nd instar larvae of C. Formosa affected the predation efficiency of C. Formosa, and the functional response to itself density can be described by E=0.460P-0.399and E=0.4528/1+0.2684(P-1), which showed the predation efficiency of C. Formosa was decreased with the increase of the larvae density and the prey of the1st instar nymphs of D. neobrevipes. Mutal interference affected the predation efficiency of C. Formosa. The intraspecific interference effects test showed with the density of C. Formosa and the number of1st instar nymphs of D. neobrevipes multiplied increased, the predation efficiency of C. Formosa was decreased. 5. The preferences of C. formosa on D. neobrevipes, Rhopalosiphum maidis Fitch and Aleurodicus dispersus RussellThe preferences of C. formosa on the D. neobrevipes, R. maidis and A. dispersus were studied in the laboratory. From the results of choice test, it was found that the number of1st～3rf instar larvae of C. formosa feed on1st instar nymphs was significantly higher than those on2nd instar nymphs,3rd instar nymphs, females of D. neobrevipes. C.formosa prefered to feed on nymphs than adults of R. maidis. The1st instar nymphs of D. neobrevipes was the most favorite for C. formosa among all supplied stages of D. neobrevipes, R. maidis and A. disperses, and nymphs of R. maidis was the second.