Ant-hemipteran association decreases parasitism of Phenacoccus solenopsis by endoparasitoid Aenasius bambawalei

Authors: XU, CHONG - Huazhong Agricultural University; LI, QIULING - Huazhong Agricultural University; QU, XIAOBIN - Huazhong Agricultural University; Chen, Jian; ZHOU, AIMING - Huazhong Agricultural University

Submitted to: Ecological Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary: Mealybugs are often tended by ants for their honeydew. It is widely accepted that ant tending facilitates the colony growth of mealybugs by protecting them from predators and parasitoids. However, few studies have explored how ant tending helps mealybugs defend against their natural enemies. Ghost ants and cotton mealybugs have a close mutual relationship and previous studies have shown that ghost ant tending can significantly reduce parasitism and visit frequency of Aenasius (A.) bambawalei, a dominant endoparasitoid of cotton mealybugs. Since ghost ant workers seldom attack this parasitoid, it is unknown how ghost ants affects the performance of this parasitoid. In this study, it was found that honeydew produced by P. solenopsis was an attractant to A. bambawalei. Parasitoids exhibited less searching activity, shorter longevity and lower parasitism when less honeydew was available. A. bambawalei also showed a significant avoidance to pygidial gland secretions and visual cues of ghost ants. Honeydew consumption by ghost ants, ant defensive secretions, and mere presence of ants may all contributed to the inhibition of the parasitism of A. bambawalei. This study provides a better understanding of the regulation mechanism in ant-hemipteran-enemy interactions.

Technical Abstract: 1. Mutualism between ants and honeydew-excreting hemipterans is ubiquitous in ecosystem. It is widely accepted that ant tending facilitates the colony growth of hemipterans by protecting them from predators and parasitoids. However, few studies have explored how ant tending helps defend against natural enemies. 2. Ghost ant Tapinoma melanocephalum and the invasive mealybug Phenacoccus solenopsis have a close mutual relationship. Previous studies have shown that ghost ant tending can definitely reduce parasitism and visit frequency of Aenasius bambawalei, the dominant endoparasitoid of P. solenopsis. However, the ghost ant workers seldom attack the parasitoids. It is still unclear how the ghost ant adversely affects parasitoids. This study explored the mechanism underlying the impacts of ants on natural enemies of the mealybugs. 3. Honeydew produced by P. solenopsis was an attractant to A. bambawalei. Parasitoids exhibited inactive searching activity, shorter longevity and slighter parasitism when supplied with less honeydew. A. bambawalei showed a significant avoidance to pygidial gland secretions and visual cues of ghost ants. Parasitism in plants treated with 6-methyl-5-hepten-2-one, actinidine, and gland extracts was significantly lower than that in plants treated with only solvent (paraffin oil or double-distilled water). 4. It is concluded that honeydew consumption by ghost ant may negatively influence the performance of parasitoids. The pygidial gland secretions and visual cues of ghost ants also largely inhibit the parasitism. These results may contribute to a better understanding of the regulation mechanism in ant-hemipteran-enemy interactions.