多异瓢虫与七星瓢虫、大草蛉不同虫态间的集团内捕食

多异瓢虫、七星瓢虫和大草蛉是控制蚜虫重要的广谱捕食性天敌昆虫,为明确这些昆虫间的集团内捕食效应与个体发育阶段的关系,观察了多异瓢虫与七星瓢虫、大草蛉各虫态(蛹除外)之间的集团内捕食效应。设置30个虫态(虫龄)组合处理,于温室盆栽棉花(无蚜虫)上接种等量的试虫,观察24 h后的存活数量。结果表明,当参与双方的虫态不同时,晚期虫态的存活数量显著大于早期虫态;当参与双方的幼虫龄期不同时,高龄幼虫的存活数量显著大于低龄幼虫;成虫对卵、1龄和4龄幼虫的捕食程度随虫龄增大而呈抛物线增大,存在显著的二次函数关系。当参与双方的虫态(龄)相同时,多异瓢虫成虫的存活数量显著小于七星瓢虫,但大于大草蛉成虫;多异瓢虫幼虫(1龄和4龄)的存活数量显著小于大草蛉,而与七星瓢虫没有显著差异。研究结果说明,在没有集团外猎物(蚜虫)存在的情况下,多异瓢虫与七星瓢虫、大草蛉之间的集团内捕食效应只在参与者的虫态或虫龄不同时取决于发育阶段,而当参与者虫态或虫龄相同时,还取决于其他因素。

Intraguild predation among predatory insects Hippodamia variegata, Coccinella septempunctata and Chrysopa pallens at different stages

The generalist predatory ladybirds Hippodamia variegata (Goeze), Coccinella septempunctata L. and the lacewing Chrysopa pallens (Rambur) are of major importance for the control of aphids on agricultural crops. To investigate intraguild predation (IGP) intensity as related to life cycle stages of involving protagnists, experiments were conducted to evaluate IGP between H. variegata and C. septempunctata and between H. variegata and C. pallens at different stages. Thirty pairs of life stages (for the exception of pupa) were tested in the greenhouse. A pair of stages with equal number of insects was released onto a potted cotton plant without the presence of aphids, and survivors were recorded 24 hours later. The results showed that in pairings between different stages of two predators, later stages survived significantly more than earlier stages. The intensity of predation of adults was dependant on earlier life stages in a quadratically functional relationship. In pairings between same stages of two predators, H. variegata adults survived less than their counterparts of C. septempunctata, but more than those of C. pallens; H. variegata larvae (L1 and L4) survived less than their counterparts of C. pallens, but equally to those of C. septempunctata. The results of this study suggested that in the absence of extraguild prey (aphids), the intraguild predation intensity among H. variegata, C. septempunctata and C. pallens may depend on life stages when different life stages are encountered, but on other factors when same life stages encounter each other.