中文摘要：

为了明确幼虫密度对草地螟Loxostege sticticalis种群增长的影响,对室内条件下（温度22±1℃,RH70%±5%,光周期16L∶8D）不同幼虫密度[1,10,20,30和40头/瓶（650mL）]饲养的草地螟生长发育及繁殖进行了研究。结果表明：幼虫密度对草地螟幼虫体色、发育历期和存活率,以及蛹重和成虫生殖等有显著影响。随着幼虫密度的增加,幼虫体色黑化程度呈增强趋势,幼虫密度大于10头/瓶时的体色黑化值均显著大于幼虫密度为1头/瓶时的体色黑化值（P〈0.05）。20头/瓶的幼虫和蛹历期最短,且随幼虫密度的增加而显著延长（P〈0.05）。幼虫存活率以10头/瓶最高,其他幼虫密度的幼虫存活率显著较低（P〈0.05）。蛹重以1头/瓶的最重,并随幼虫密度增加而显著下降（P〈0.05）。成虫产卵量和交配率分别以1和20头/瓶的幼虫密度最高,幼虫密度升高则产卵量、交配率逐渐降低。成虫产卵历期随着幼虫密度的增加逐渐缩短。雌、雄蛾寿命分别以10和20头/瓶幼虫密度时最长,幼虫密度过高时雌雄蛾寿命又显著缩短（P〈0.05）。生命表分析表明,幼虫密度对草地螟种群增长指数有显著影响,以10头/瓶幼虫密度的种群增长指数最高,幼虫密度过高或过低时种群增长指数下降。据此认为,幼虫密度是影响草地螟种群增长的重要因子之一。

英文摘要：

To investigate the effects of larval density on the population growth of the beet webworm,Loxostege sticticalis,the larval duration and survival,pupal weight and adult fecundity were examined by rearing larvae at the densities of 1,10,20,30 and 40 larvae/650 mL jar under laboratory conditions（22±1℃,RH 70% ±5%,photoperiod 16L：8D）.The results showed that larval cuticular color,developmental duration and survival,pupal weight and adult fecundity of L.sticticalis were significantly affected by larval density.Larval cuticular melanization score became greater as the density increased,and the scores at the densities exceeding 10 larvae per jar were significantly higher than that at the density of one larva per jar（P〈0.05）.The developmental time of larva and pupa at the density of 20 larvae per jar was the shortest,while it was significantly prolonged as the larval density increased（P〈0.05）.The larval survival rate was the highest at the density of 10 larvae per jar,which was significantly higher than those at other densities（P〈0.05）.Pupal weight was the heaviest at the density of one larva per jar,and it was significantly reduced with the increase of larval density.The total fecundity per female and the proportion of mating individuals were the highest at the density of one larva and 20 larvae per jar,respectively,and they decreased as larval density increased.Adult oviposition duration was gradually shortened with the increase of larval density.The longevity of female and male was the longest at the density of 10 and 20 larvae per jar,respectively,while it was significantly shortened when larval density was too high.Life table analysis indicated that the population growth index was significantly affected by larval density,and it was the highest at the density of 10 larvae per jar,but lower at either higher or lower density.It is so concluded that larval density is one of the major factors influencing population growth in L.sticticalis.