When confined to a single leaf, the larvae of most leafminers should suffer intense intraspecific competition. The survival and performance of individuals are expected to decline with increasing larval density within a leaf, showing a negative density-dependent effect. The maximum density of an Elachista Treitschke(Lepidoptera:Elachistidae) miner on Indocalamus tessellatus(Munro)Keng f.(Poaceae: Bambusoideae) under natural conditions can be greater than 40 per leaf, making this a good system for studying intraspecific competition and density effects.We counted the number of leaves with different mine densities in the field and found a clumped distribution of leafminer larvae among host leaves. The emergence rates of pupae(and last-instar larvae), adults and parasitoids were inversely correlated with larval density. Pupal weight and adult weight also showed negative relationships with larval density. However, pairwise tests showed that there might be no differences in pupal or adult weight at larval densities of 1–10 mines per leaf, indicating that densitydependent effects are more obvious at densities greater than 10 mines per leaf. Intraspecific competition could lead to stable density and consistent body size in surviving individual insects, which would help maintain a sustainable population size. The density threshold could be an indicator of the balance between intraspecific competitive detriments and conspecific aggregation benefits; however, the validity of the threshold density hypothesis requires further testing and confirmation.
近期在辽宁柞蚕区发现了一种新的柞树潜叶性害虫。将昆虫线粒体细胞色素C氧化酶亚基Ⅰ基因（mtD NA COⅠ）序列作为DNA条形码,结合形态特征对害虫进行分类鉴定。以单头试虫的基因组DNA为模板,用mtD NA COⅠ通用引物PCR扩增得到了试虫的mtD NA COⅠ基因片段（GenB ank登录号：KX657707~KX657709）。将获得的基因片段序列在NCBI数据库进行BLAST同源性搜索,在GenB ank中未搜索到该试虫的相关序列信息,但与鞘翅目Coleoptera象甲科Curculionidae象甲亚科Curculioninae的Orchestes jota mtD NA COⅠ同源片段序列（GenB ank登录号：KJ963227.1）的相似度最高,为86%。室内观察其成虫、幼虫和蛹的形态特征：成虫体长3.7~4.0 mm,喙长0.8~1.0 mm,鞘翅,后足发达,腿节粗壮;老熟幼虫5~7 mm,体节12节,无足,具步泡突;蛹为裸蛹。基于试虫的mtD NA COⅠ分子鉴定标记,结合试虫与原有记录形态特征的比较结果,初步鉴定新发现的柞树潜叶性害虫为跳象亚科Rhynchaeninae跳象属Rhynchaenus的多斑柞跳象Rhynchaenus（Orchestes）maculosus。
