Movement of three aphidophagous ladybird species between alfalfa and maize revealed by carbon and nitrogen stable isotope analysis

The movement between alfalfa and maize of three of the most common aphidophagous coccinellids in southern Europe was determined using carbon and nitrogen stable isotope analysis at four periods during the growing season. The isotope analysis revealed movement between alfalfa and maize but patterns were different between the three species. While Coccinella septempunctata L. (Coleoptera: Coccinellidae) only moved from alfalfa to maize, Propylea quatuordecimpunctata L. (Coleoptera: Coccinellidae) continuously dispersed between the two adjacent crops. Hippodamia variegata Goeze (Coleoptera: coccinellidae) showed an intermediate pattern. Results suggest that, while alfalfa acts as a source of the three species to maize, maize also plays a role as a source of P. quatuordecimpunctata and H. variegata to alfalfa. The specific movement traits that emerged for the three coccinellid species suggest that crop management affects them differently and point out that the association between crops is very valuable for improving coccinellid biological control services.