The population density of Eucallipterus tiliae (L.) (Hemiptera: Aphididae) required for initiating oviposition in Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) was established in Tilia cordata Mill. (Dicotyledoneae: Tiliaceae) stands sampled weekly throughout the vegetative seasons of 2017–2019. The number of aphids per leaf area and oviposition in H. axyridis females were determined at each sampling session. Seasonal changes in aphid abundance and the presence of ovipositing females in natural populations varied across years but in all years H. axyridis started oviposition as soon as the aphid density increased above 10.2 aphids per ten sweeps, which equals 1.04 aphids per 100 cm² leaf area. These values exceed the threshold aphid density for starting oviposition in Coccinella septempunctata L. (Coleoptera: Coccinellidae), which is 0.40 aphids per 100 cm² leaf area. This difference is in line with H. axyridis preference for trees, host plants with complex architecture and hard to search, and preference of C. septempunctata for spatially simple herbs.

中文翻译：

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蚜虫开始产卵的门槛蚜虫种群密度

在Tilia cordata Mill中建立了启动异色Harmonia axyridis（Pallas）（鞘翅目：Coccinellidae）产卵所需的Eucallipterus tiliae（L。）（半翅目：蚜虫）的种群密度。（Dicotyledoneae：ilia科）在2017-2019年的整个营养旺季每周采样一次。在每个采样阶段确定腋生腋臭雌虫每叶面积和产卵的蚜虫数量。在蚜虫数量和产卵在自然种群跨越年不等，但在所有岁的女性存在季节性变化异色瓢虫开始产卵只要蚜虫密度上述每十分扫描10.2蚜虫，相当于每100cm 1.04蚜虫增加²叶面积。这些值超过了在七星瓢虫中开始产卵的阈值蚜虫密度（鞘翅目：球藻），每100 cm ²叶面积有0.40个蚜虫。这种差异与H.axyridis对树木的偏爱，结构复杂且难以搜寻的寄主植物以及C. septempunctata对空间简单草药的偏爱相符。