| Tytthus chinensis Stal (Hemiptera:Miridae) is a predator in agroecosystem, which feed on eggs of the brown planthopper, Nilaparvata lugens (Stal), the white-backed planthoper, Sogatella furcifera(Horvath) and the small brown planthopper, Laodelphax striatellus (Fallen), the three most destructive rice insect pests in Asia rice production regions. The species was reported to occur widely in Zhejiang, Jiangxi, Fujian, Hainan Taiwan and other southern provinces in China, Korea, Southern-Eastern Asia, Australia and Indo-Pacific Islands. Given that this mirid has the potential to a predominant biological control agent in rice ecosystem, and essential data of development, survival and fecundity haven’t been reported yet. Therefore, the research on population parameters of life table of T. chinensis has been necessitated considerably, helping develop the effect of T. chinensis in integrated pest management.1. Effects of constant temperature on development and reproduction of Tytthus chinensis (Stal)Life table of the laboratory population of Tytthus chinensis (Stal) was conducted at five different constant temperatures (14,18,22,26and30℃). The results showed that the developmental rate of T. chinensis increased with increasing temperature between18℃and30℃, and the relationship between them could be simulated by Logistic model. The developmental durations of nymph and egg varied from9.1d at30℃to16.8d at18℃and from6.0d at30℃to24.2d at18℃within experimental temperature ranges, respectively. The developmental threshold temperature and effective thermal accumulations for egg, nymph, and whole immatural stage was11.3,9.5and12.4℃and112.9,185.7and268.2degree-days respectively. The net reproductive rate reached maximum (43.5) at26℃, the maximum fecundity was231.2at22℃, and the sex ratio(i.e. proportion of female) reached highest (0.58) at26℃. The intrinsic rate of increase and finite rate of increase reached maximum at30℃, were0.169and1.180, respectively. Therefore, we concluded that26～30℃is a optimal temperature ranges for T. chinensis.2. Influence of the prey species on the life history parameters of T. chinensisThe characterstic of development and fecundity of Tytthus chinensis Stal attacking there different preyspecies of rice planthopper (N. lugens, S. furcifera, L. striatellus) were studied under laboratory conditions. We found that consumption of different preys had significant influences on the nymph developmental duration, egg’s incubation period and mean generation time of T. chinensis. When the brown planthopper was provided as predation resources, the immature developmental duration of T. chinensis reached maximum compared with two other rice planthoppers. The pre-oviposition period was the longest on the white-backed planthopper, and the shortest on BPH. The immature total generation durationhave a maximum value (17.00d) on WBPH,The survival of immatural stages was lowest on SBPH, approximately40%of eggsdeveloped to adults, comparing with WBPH and BPH. The sex ratio, fecundity (eggs of per female adult) and net production rate (Ro) reach a maximum of78.9on WBPH, whereas the minimum value (23.2) on SBPH. The intrinsic rate of increase (rm) and finite rate of increase λ get largest value (0.154and1.167) on BPH, by contrast least value (0.107and1.112)on SBPH. Considering rm a significant index which affected on T. chinensis on different prey resources, T. chinensis was mostly suitable to live on BPH. Therefore, our finding can provide an appropriate method for biological control of rice planthoppers.3. The influences of rice varieties on suitability of T.chinensisLife tables of T. chinensis were constructed under experimental condition (14L:10D,26±1℃, RH60±10%), maintaining on the preys Nilaparvata lugens (Stal), to determine the influences of rice varieties with different BPH-resistant (Taipingxian, Xiushuil34, IR64, TN1). We found that the developmental period of T. chinensis egg was the shortest on TN1compared with other three rice varieties, and the hatchability was maximum on IR64, with an exceeding70%, less than50%of minimum value on Xiushuil34, and the nymphal survival was not significant different among the four different resistant rice varieties. The max. and min. values of adult sexual ratio respective were and0.310and0.182on TN1and Xiushuil34. Fecundity per female reached a max. value on TNI and a min. value on Taipingxian respectively. The values of the intrinsic increase rate and the finite increase rate were0.140,0.133,0.117and0.116(?)/(?)/d,1.151,1.142,1.124and1.222times/don TN1, IR64, Xiushui134and Taipingxian, respectively.4. Ecological geographical suitability ananlysis of T.chinensis with MaxEnt modelBy using the MaxEnt model together with the known geographical distribution of T.chinensis,.suitable geographical distribution area of T.chinensis were predicated mostly in southeast China, east Asia, southeast Asia and parts of the Indonesian islands etc., i.e. within the geographical biomes of Oriental and Australian. We also found that precipation of the warmest seasons, precipation in June and mean Diurnal Range monthly affected greatly ecological suitability of T.chinensis, when precipation of warmest seasons and precipation in June exceeded500mm and200mm respectively, and mean Diurnal Range monthly is below20℃, it is suitable for T. chinensis... |
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