Many ant species tend aphids in order to harvest their high-carbohydrate honeydew and part of this tending behavior includes defending the aphids from predators and parasites. However, one beetle, the Louisiana lady beetle, Scymnus louisianae, is a predator that specializes in attacking ant-tended aphids. Its specialization relies on a unique cuticular-based protection that allows it to resist ant aggression. We studied the physical and chemical basis of this cuticular defense in relation to the cornfield ant, Lasius alienus, which tends the soybean aphid, Aphis glycines. Through behavioral bioassays and gas chromatography-mass spectrometry (GC-MS) analysis, we found that the beetle's cuticular waxes block L. alienus' ability to perceive cues that would otherwise enable them to distinguish this lady beetle from other objects in the environment. Ants responded more aggressively toward beetles that were denuded of their cuticular structures compared to undisturbed beetles or beetles with cuticular compounds reapplied from solution. Furthermore, GC-MS analysis confirmed the existence of compounds present on the cuticular surface not present in the outer cuticular structures and identified other compounds involved in this novel form of chemical camouflage.
Species 1: Coleoptera Coccinellidae Scymnus louisianae
Species 2: Homoptera Aphididae Aphis glycines (soybean aphid)
Species 3: Hymenoptera Formicidae Lasius (cornfield ant)
Keywords: cuticular defense, chemical ecology
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