高幼虫密度胁迫对二化螟生长发育的影响

为明确二化螟幼虫群集密度对种群增长的影响,在室内用人工饲料饲养比较了不同幼虫密度对二化螟生长发育的影响。结果表明,高幼虫密度800头/盒胁迫下,二化螟雌、雄幼虫和蛹的发育更快,其幼虫+蛹历期分别比低密度100头/盒处理要快8.0 d和6.0 d;化蛹率和羽化率较100头/盒处理分别显著下降了25.7和25.0个百分点,且雌、雄蛹重分别减少了9.4 mg和4.8 mg;但对二化螟成虫性比、寿命、产卵量和卵孵化率无显著影响。低密度100头/盒处理下二化螟幼虫发育最好,其种群增长指数为56.9,化蛹率达61.4%,羽化率达57.7%,雌、雄蛹重分别为58.3 mg和43.0 mg,但其幼虫+蛹历期较长,雌虫为58.5 d,雄虫为53.9 d。高密度800头/盒胁迫下二化螟幼虫发育最差,其种群增长指数仅为24.1,化蛹率仅为35.7%,羽化率为32.7%,雌、雄蛹重分别为48.9 mg和38.2 mg,但其幼虫+蛹历期较短,雌虫为50.5 d,雄虫为47.9 d。表明在恒定的空间和有限的食物中,幼虫密度过大会导致种内竞争加剧,使得幼虫可能倾向以更快的速度化蛹,确保其存活率以更好地繁殖后代。

Effects of high larval density stress on growth and development of Chilo suppressalis Walker (Lepidoptera:Pyralidae)

To investigate the effects of larval density on the population parameter of Asiatic rice borer Chilo suppressalis, the development and reproduction of this insect pest were analyzed under five larval densities in the laboratory. Female and male larvae and pupae developed rapidly under the high larval density of 800 neonate larvae/diet jar, and the larval and pupal durations were 8.0 and 6.0 days shorter, respectively, than those of the individuals reared at the low density of 100 neonate larvae/diet jar. Meanwhile, the survival rate of larvae+pupae and eclosion rate were reduced by 25.7 and 25.0 percentage points, and female and male pupal weights were decreased by 9.4 mg and 4.8 mg. But sex ratio, adult longevity, fecundity and egg hatching rate were not significantly affected by larval density. The larval development of C. suppressalis was the best at the density of 100 neonate larvae/diet jar, with a population growth index of 56.9, pupation rate of 61.4%, eclosion rate of 57.7%, and female and male pupal weights of 58.3 mg and 43.0 mg, respectively, but their durations of larval+pupal stages were longer (female was 58.5 d, male was 53.9 d). The larval development of C. suppressalis was the worst at the density of 800 neonate larvae/diet jar, with a population growth index of 24.1, pupation rate of 35.7%, eclosion rate of 32.7%, and female and male pupal weights of 48.9 mg and 38.2 mg, respectively, but their durations of larval+pupal stages were shorter (female was 50.5 d, male was 47.9 d). The limited space and food under a high larval density might increase the strength of intraspecific competition, and it might be advantageous to pupate at faster development and ensure survival till reproduction.