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Molecular gut-content analysis has revolutionized the study of predator-prey interactions and allowed the accurate description of food webs in the field. In this study, we identified and characterized cytochrome c oxidase subunit 1 (CO1) from the aphid Megoura japonica (Homoptera: Aphididae) and characterized its utility for molecular gut-content research. Coccinella septempunctata (Coleoptera: Coccinellidae) were selected as a representative predator of two insects, M. japonica and Aphis craccivora (Homoptera: Aphididae), for analysis of predator-prey interactions using prey-specific PCR and reverse-transcription quantitative PCR (RT-qPCR). The results of prey-specific PCR showed that with increasing M. japonica consumption, the MjCO1 PCR band was brightened and subsequently decreased with extended digestion time. RT-qPCR using Taqman-MGB fluorescence probe was also utilized to quantify predator-prey interaction between C. septempunctata and M. japonica. The MjCO1 copy number in C. septempunctata increased with greater consumption of M. japonica. Moreover, MjCO1 copy number in C. septempunctata decreased with increasing digestion time. Furthermore, analysis of CO1 copy numbers in the gut of C. septempunctata showed no feeding preference between M. japonica and A. craccivora. Our results demonstrate the utility of molecular gut-content analysis in understanding trophic relationships between these ladybirds and aphids. In addition, RT-qPCR is shown to be an effective and accurate method that should be considered for wider application in predation studies in field settings.

High plant biodiversity and landscape food provision stability is known to have a positive impact on biocontrol services provided by natural enemies. However, few studies have assessed how differential spatial and temporal crop richness actually impact biocontrol services, and notably how natural enemies may spill-over among crops. Within this framework, using a four-cage maze system under laboratory conditions, we evaluated the effect of a diversified crop system (four crops, namely cotton, tomato, squash and soybean) and low diversified crop systems (one single crop), on the generalist predator Harmonia axyridis (Pallas) and its predation capacity on aphids. The system varied food availability both in space, i.e. different cages, and in time, i.e. different dates of resources implementation. In general, the effects of crops on the natural enemies’ traits observed in the diversified crop system resulted from the average effects of the individual low diversified crop systems; the impact of the predator was highly dependent on the plant. Low diversified crop systems actually proved to be either very suitable for the predator’s development (tomato and squash), or not at all (soybean and cotton), but inversely suitable in reducing pest population with lower efficacy in tomato and squash and higher efficacy in soybean and cotton. The spillover of the ladybird was strongest in the squash low diversified crop system and lowest in the cotton one, other systems showing intermediate spillover values. In the diversified crop system, the ladybird presence was always closely related to plant presence, and aphid populations were maintained at a stable population increase. Still, the predator was also found in cages lacking plants, as opposed to the low diversified crop systems; this hinted at the potential of the highly diversified crop system to promote ladybird dispersal and increase foraging activity. We demonstrate that increasing crop diversity in agroecosystems may help promote biocontrol services provided by H. axyridis by promoting its spillover between crops (e.g. while the plants are senescing and/or when they are harvested).