Ants impact the energy reserves of natural enemies through the shared honeydew exploitation

1. Ants, as well as many species of parasitoids and predators, rely on sugar-rich foods such as honeydew to fulfill their energetic needs. Thus, ants and natural enemies may interact through the shared honeydew exploitation. 2. Ant-exclusion experiments were performed in a citrus orchard to test the hypothesis that ants may impact the energy reserves of predators and parasitoids through the competition for honeydew. Through the use of high-performance liquid chromatography (HPLC) the level of ant activity with the energy reserves and feeding history of individual specimens collected in the field during representative days of spring, summer, and autumn were related. 3. Out of 145 Aphytis chrysomphali Mercet parasitoids captured in the field, 65% were classified as sugar-fed and 24.7% as honeydew-fed. In summer, when ant activity peaked, there was a significant negative correlation between the level of ant activity and the total sugar content and honeydew feeding incidence by A. chrysomphali. Out of 47 individuals of the predator Chrysoperla carnea sensu lato (Stephens), captured in the field, 55.3% were classified as sugar-fed. We found a significant negative effect of the level of ant activity on the sugar-feeding incidence by C. carnea in spring. 4. The present study provides evidence that ants can interfere with the energy reserves of natural enemies. This interaction may be widespread in various ecosystems with important consequences for the arthropod community composition and with practical implications for biological control given that absence of sugar feeding is detrimental for the fitness of many species of predators and parasitoids.