The multicolored Asian ladybeetle, Harmonia axyridis Pallas (Col, Coccinellidae), is recognized as one of the most invasive insects in the world. It has reduced the native coccinellids populations in several areas, and it is considered a threat for biodiversity at large. A significant trait, favoring its invasiveness and its dominance over indigenous ladybeetles, is intraguild predation (IGP). IGP has advantageous adaptive value for individuals: removing competitors and potential predators, and providing an alternative nutritive resource when main resources are scarce. IGP can be affected by several factors, but little is known about the effect of pesticides on this behavior. Previous research demonstrated that the invasive Asian ladybeetle is highly susceptible to the reduced-risk insecticide novaluron, a chitin synthesis inhibitor, whereas the North American indigenous competitor, Coleomegilla maculata DeGeer (Col, Coccinellidae), is not. Our study explores the adaptive value of IGP for each of the two coccinellids after preying on each other’s larvae, which were previously treated with insecticide. Our first hypothesis is that the invasive ladybeetle, susceptible to the insecticide, should lose the adaptive value of IGP. Our second hypothesis is that the adaptive value of IGP for the invasive predator will recover over time, because of neutralization of the insecticide by the intraguild prey. The results confirm both hypotheses and show that an insecticide can completely remove the adaptive value of IGP for the invader, while the adaptive value of IGP does not change for the indigenous ladybeetle. Moreover, the study demonstrates that if the intraguild prey (non-susceptible to the insecticide) undergoes molt after being exposed to the insecticide, the adaptive value for the intraguild predator is restored.

多彩多姿的亚洲瓢虫，Harmonia axyridisPallas (Col, Coccinellidae)，被公认为世界上最具入侵性的昆虫之一。它减少了几个地区的本地瓢虫种群，它被认为是对整个生物多样性的威胁。一个显着的特征，有利于其入侵性和对本土瓢虫的支配地位，是公会内捕食 (IGP)。IGP 对个体具有有利的适应性价值：去除竞争者和潜在的掠食者，并在主要资源稀缺时提供替代营养资源。IGP 可能受到多种因素的影响，但关于杀虫剂对这种行为的影响知之甚少。先前的研究表明，侵入性亚洲瓢虫对降低风险的杀虫剂 novaluron（一种几丁质合成抑制剂）非常敏感，而北美本土竞争对手，黄斑鞘翅目DeGeer (Col, Coccinellidae), 不是。我们的研究探讨了两种瓢虫在捕食彼此的幼虫（先前用杀虫剂处理过）后，IGP 对每一种的适应性价值。我们的第一个假设是，对杀虫剂敏感的入侵瓢虫应该失去 IGP 的适应性价值。我们的第二个假设是，由于公会内猎物对杀虫剂的中和作用，IGP 对入侵捕食者的适应性值会随着时间的推移而恢复。结果证实了这两个假设，并表明杀虫剂可以完全消除 IGP 对入侵者的适应值，而 IGP 对本地瓢虫的适应值没有改变。而且，