《环境昆虫学报》

美国白蛾Hyphantria cunea原产于北美地区，1979年首次在我国辽宁省丹东地区发现，目前已扩散至江苏省南京市等地区，并有进一步扩散的趋势。由于其寄主范围广，适应能力强，危害严重，因此给我国林业生产造成了重大损失。美国白蛾1~4龄幼虫常聚集危害，4龄后开始破网分散危害。本文旨在探明幼虫密度变化对其生活史参数的影响，为解析美国白蛾种群动态变化规律提供科学依据。于温度25℃±1℃和光周期16 L∶8 D条件下，设置5头、10头、20头、40头和80头幼虫/容器5个密度处理组，待幼虫化蛹和成虫羽化后，分别检测幼虫龄期与成活率、蛹的体型（体长和体宽）与体重及成活率、成虫体型（成虫头幅宽度、前翅长度和后足腿节长度）与寿命及繁殖力等生活史参数。结果表明，幼虫密度增加缩短了幼虫发育历期，同时降低了幼虫成活率。幼虫密度增加对蛹重、蛹长、雌蛹宽度及蛹成活率有明显的负效应，但对雄蛹宽度无显著影响。幼虫密度增加对雌虫头幅宽度、雌虫繁殖力、成虫寿命与卵直径具明显负面影响，对雄虫头幅宽度与雌虫前翅长度无显著影响，对成虫后足腿节长度、雄虫前翅长度则具正面影响。因此，本研究表明幼虫密度对美国白蛾不同阶段的生活史参数具调控作用，其中幼虫密度增加对幼虫成活率、蛹的体型与体重及成活率、雌虫繁殖力与卵直径及成虫寿命的负面影响对其种群适合度可能是不利的；然而，成虫对幼虫密度增加会采取一定的适应策略，高密度条件下羽化的成虫具较长的后足腿节与前翅长度以提高其迁移扩散半径，有助于减轻子代种内竞争压力，进而提高种群适合度。

英文摘要:

The fall webworm, Hyphantria cunea (Drury) (Lepidoptera: Arctiidae), is native to North America and was introduced into China in 1979 in Dandong City, Liaoning Province. Since then fall webworm has expanded from Dandong City to the Nanjing City, Jiangsu Province. Due to its wide range of food plants and high adaptability, fall webworm has caused severe forestry production losses in China. The fall webworms were aggregated in the larval stage. This study aimed to clarify the influence of larval density on their life history parameters, and that might provide a scientific basis for analyzing their population dynamics. The larvae were reared with 5, 10, 20, 40 and 80 individuals per container (10 cm dia.×4 cm high) under L∶D=16 h∶8 h and 25℃±1℃, and the life history parameters such as the larval instar, survival dynamics, body size (mass), pupae weight, pupal body size, lifespan and fecundity of adults were investigated, respectively, after larvae pupation and adult eclosion. The larval development period and the survival rate decreased as the larval density increased. The increase of larva density had a significant negative effect on pupal weight, pupal length, female pupal width and pupal survival rate, without significant effect on male pupal width. The increase of larva density had a significant negative effect on head width and fecundity of female, lifespan of adult and egg diameter, had no effect on head width of male and length of fore wing of female, but had positive effects on length of hind femur of adults and length of fore wing of male. Therefore, the present study showed that larval population density could affect their life history parameters of H. cunea. The negative effects of increasing larval density on larval survival rate, body mass and size of pupae and pupal survival rate, fecundity of female, lifespan of adult and egg diameter would be unfavorable to the population fitness. However, the adult of H. cunea had developed adaptation strategies to the variation of larval density. Under the condition of high density of larvae, the adults with longer length of hind femur and length of fore wing would find new hosts through dispersal behavior, which would lower the intraspecific competition pressure of offspring and improve the fitness of population.

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