Differential susceptibility of Coleomegilla maculata (Coleoptera: Coccinellidae) and Scymnus creperus (Coleoptera: Coccinellidae) larvae to aggression by Solenopsis invicta (Hymenoptera: Formicidae) workers

Authors: Riddick, Eric; WU, ZHIXIN - US Department Of Agriculture (USDA); Chen, Jian

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2023
Publication Date: 3/26/2023
Citation: Riddick, E.W., Wu, Z., Chen, J. 2023. Differential susceptibility of Coleomegilla maculata (Coleoptera: Coccinellidae) and Scymnus creperus (Coleoptera: Coccinellidae) larvae to aggression by Solenopsis invicta (Hymenoptera: Formicidae) workers. Insects. https://doi.org/10.3390/insects14040318.
DOI: https://doi.org/10.3390/insects14040318

Interpretive Summary: Biological control of aphids by aphid-eating lady beetles (coccinellids) is often hampered by aphid-tending ants or aggressive, invasive ants foraging for food. Aggressive species, such as the imported fire ant (Solenopsis invicta) may attack and kill lady beetle larvae. This study tested the hypothesis that wax-secreting Scymnus creperus larvae are less susceptible than non-wax secreting Coleomegilla maculata larvae to S. invicta aggression. Laboratory experiments were setup using bird cherry-oat aphid nymphs and adults (as prey for coccinellids) on barley leaves with either lady beetle species with or without fire ant workers. Results revealed that the presence of fire ants reduced aphid predation by C. maculata but not S. creperus. The frequency of fire ant attack was greater on C. maculata than S. creperus; mortality was significantly greater for C. maculata than S. creperus. The wax covering over S. creperus reduced fire ant aggression. Unexpectedly, S. creperus larvae with wax cover removed did not suffer greater fire ant attacks or increased mortality. In conclusion, the wax cover and, perhaps, volatile or non-volatile compounds in the wax and on the integument of S. creperus larvae reduce fire ant aggression. Further research could identify wax compounds and determine their role as potential repellents or irritants against fire ants.

Technical Abstract: Biological control of aphids by aphidophagous coccinellids is often hampered by aphid-tending ants or aggressive, invasive ants foraging for food. Aggressive species such as the imported fire ant Solenopsis invicta Buren may attack and kill coccinellid larvae. This study tested the hypothesis that wax-secreting Scymnus creperus Mulsant larvae are less susceptible than non-wax-secreting Coleomegilla maculata (DeGeer) larvae to S. invicta aggression. Laboratory experiments were set up using bird cherry-oat aphid Rhopalosiphum padi (L.) nymphs and adults (as prey for coccinellids) on barley leaves in arenas with either coccinellid species and with or without S. invicta workers. The presence of S. invicta reduced aphid predation by C. maculata but not S. creperus. The frequency of S. invicta attack was greater on C. maculata than S. creperus; mortality was significantly greater for C. maculata than S. creperus. The wax covering over S. creperus reduced S. invicta aggression. Unexpectedly, S. creperus larvae with the wax cover removed did not suffer more S. invicta attacks or increased mortality. In conclusion, the wax cover and, perhaps, volatile or non-volatile compounds in the wax and on the integument of S. creperus larvae reduce S. invicta aggression. Further research could identify wax compounds and determine their functionality as semiochemicals against S. invicta.