| Summary: | The 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 <i>Solenopsis invicta</i> Buren may attack and kill coccinellid larvae. This study tested the hypothesis that wax-secreting <i>Scymnus creperus</i> Mulsant larvae are less susceptible than non-wax-secreting <i>Coleomegilla maculata</i> (DeGeer) larvae to <i>S</i>. <i>invicta</i> aggression. Laboratory experiments were set up using bird cherry-oat aphid <i>Rhopalosiphum padi</i> (L.) nymphs and adults (as prey for coccinellids) on barley leaves in arenas with either coccinellid species and with or without <i>S</i>. <i>invicta</i> workers. The presence of <i>S</i>. <i>invicta</i> reduced aphid predation by <i>C</i>. <i>maculata</i> but not <i>Sc</i>. <i>creperus</i>. The frequency of <i>S</i>. <i>invicta</i> attack was greater for <i>C</i>. <i>maculata</i> than <i>Sc</i>. <i>creperus</i>; mortality was significantly greater for <i>C</i>. <i>maculata</i> than <i>Sc</i>. <i>creperus</i>. The wax covering on <i>Sc</i>. <i>creperus</i> reduced <i>S</i>. <i>invicta</i> aggression. Unexpectedly, <i>Sc</i>. <i>creperus</i> larvae with the wax cover removed did not suffer more <i>S</i>. <i>invicta</i> attacks or increased mortality. In conclusion, the wax cover and, perhaps, the volatile or non-volatile compounds in the wax and on the integument of <i>Sc</i>. <i>creperus</i> larvae reduce <i>S</i>. <i>invicta</i> aggression. Further research could identify the wax compounds and determine their functionality as semiochemicals against <i>S</i>. <i>invicta</i>.
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