| Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), distributes widely in over 90 countries and regions in tropical, subtropical and temperate areas. Damages of B. tabaci to host plants include direct feed on plant phloem sap, transmit plant viruses, and cause physiological disorder of plants. After the introduction of B. tabaci B-biotype into China in 1990s, it has spread rapidly and broken out in many provinces, causing severe economic lost in agriculture. Many former studies show that the adaptability of B. tabaci B-biotype to high temperature stress is one of the key mechanisms of its successful invasion and expansion throughout the world. Under the trend of global warming, the tolerance of B. tabaci B-biotype to high temperature stress could make it dominate in the competition with and replacement of other species. This stdudy aims to: (1) compare the population dynamics, sex ratio and fecundity of B. tabaci B-biotype under optimal and high temperatures, (2) compares its courtship and copulation behavior under optimal and high temperatures, (3) compare the fecundity of B. tabaci after short-term exposure of its eggs to high temperatures. The main results are as follows:1. Development, population dynamic and fecundity of B. tabaci B-biotype under high temperatures for five successive generationsEgg hatching rate, population dynamic, bacteriome-absent rate, survival rate of bacteriome-absent individuals, adult sex ratio, and fecundity of B. tabaci B-biotype were observed for five successive generations at 27, 31, 35, 37℃. The results showed that the factors of temperature and generation have significant impacts on the above indices. Population dynamics and sex ratios differed significantly among temperatures and generations. The fitness of B. tabaci populations decreased with the increasing temperatures and generations., Egg hatching rate dropped from 98.9% at 27℃(control) to 52.3% at 35℃for the fifth generation. The survival rate decreased signigicantly and the development slowered significantly from egg to newly eclosed adult at 35℃for the fourth and fifth generation than those at 27℃. Bacteriome-absent offspring were observed in the fourth and fifth generations at 31℃, and from the first generation and on at 35℃with a rate increasing from 0.3% to 6.8%. The survival rates of the bacteriome-absent offspring at different treatments did not differ significantly. For the female adult, its pre-oviposition period and longeivity were shortened, and the fecundity was lower with the increasing temperatures.2. Courtship and copulate behavior of B. tabaci B-biotype under different temperaturesUsing the video camera recording method, the courtship and copulate behavior of B. tabaci B-biotype under 27 and 31℃were recorded for 48h.. Searching period, courtship duration, copulation duration, copulation interval, and copulation frequency were calculated after playing back the records. The results indicated that the average copulation frequency of B. tabaci mate was 2.6 times at 31℃, which was significantly less than that at 27℃(3.4 times). The searching period and copulation duration during the first copulation process were shortened by 48% and 56% at 31℃than at 27℃. The courtship duration at 31℃was also shortened at an insignificant level than at 27℃. For the second copulation process, the copulation duration was shortened by 74% at 31℃than at 27℃. But the searching period, courtship duration and courtship interval did not differ significantly between 27℃and 31℃.3. Effects of different exposure time and high temperature on the survival and fecundityTo reveal the reactions of B. tabaci B-biotype to heat stress, effects of short-term (1 h, 2 h and 4 h) exposure of B. tabaci eggs to high temperature (39℃and 41℃) on the survival and fecundity were studied. Survival rates after exposure to 41℃for 1 h and 4 h were significantly lower. Female ratio of B. tabaci after exposure to 41℃for 1 hour was 61.3%.The longevity prolonged and the pre-oviposition period shortened. The oviposition rhythms and age-specific adult survival rates change. These results showed that short-term exposure of B. tabaci to high temperature at egg stage decreased its survival rate, whereas increased its fecundity.4. ConclusionComparing with the control at 27℃, the fitness of B. tabaci B-biotype decreased to some extents after successive rearing atr 31℃and 35℃for 1 to 5 generations, regarding the indices of egg hatching rate, survival, development and bacteriome-absent rate. The copulation frequency and copulation duration shortened at 31℃. The pre-oviposition periods of B. tabaci decreased under successive rearing under continous high temperatures or under short-term high temperature exposure weres shorten, and the longevity and fecundity of female adults were decreased uner successive rearing under continous high temperatures, but risen under short-term high temperature exposure...
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