Intraguild Predation On An Aphid Parasitoid Aphelinus Asychis(Hymenoptera: Aphelinidae)by A Ladybird Beetle Harmonia Axyridis(Coleoptera: Coccinellidae)

Nowadays, the quality and safety of agricultural products are more and more important. Biological control isa healthy and efficient way to manage agricultural crops. Recently, the application of biological control develops more quickly in China. In biological control of insect pests, a number of control agents are commonly used together. Intraguild predation(IGP), which may limit the effectiveness of the controlWe used ‘Myzuspersicae- Harmonia axyridis-Aphelinusasychis’ system to study the IGP on parasitoidsby ladybirds in the laboratory, and the performance of ladybirds on the parasitoid mummies and internal reasons would be investigated, in order to provide references for the biological control of aphids in the future. Our results were showed as follow:1. The H. axyridis reared on unparasitizedaphids or artificial diet showed a preference foraphids. The H. axyridis reared on parasitized aphidshad no preference for aphids because of the similar number of aphids and mummies consumed by them.2. Ladybirds were allowed to select between aphids and mummies presented in the same total numbers(20) but with ratios of 15:5, 10:10 and 5:15. They selected more mummies when mummies were more abundant and more aphids when aphids were more abundant. When numbers were equal, they consumed more aphids than mummies. However, the rejection rates on first encounter not to proceed to consumption were much greater for mummies(36%) than aphids(2%) at all densities.3. The developmental time of ladybirds reared on mummies was not different with those reared on aphids. The weight of larvae feeding on aphids and mummies was similar. The adults fed on aphids were significantly heavier than those fed on mummies.4. Mummies were twiceas rich in proteins and lipids as aphids. Aphids had more carbohydrate than mummies. In the content of nutrition components, the ladybird adults reared on aphids had no difference with those reared on mummies.In conclusion, prior feeding experience of H. axyridis could affect their prey preference. When the numbers of aphids and mummies were different, ladybirds still chose to consume aphids and more mummies were rejected. Their prey preference could not be affected by the prey density. Although feeding on mummies of A. asychis would not produce a negative effect on the growth of H. axyridis, ladybirds would avoid feeding on mummified aphids containing. H. axyridis could be expected to add to the biological control caused by A. asychis.