The interplay of olfaction and vision in host plant selection by Anthrenus verbasci

Anthrenus verbasci is commonly associated with museums, where the larvae can destroy valuable collections and displays. In households they are a nuisance; carpets, fabrics, food-items, or any proteinaceous material can be damaged. Little is known about the host preference of adults, they are frequently seen on plants of the Apiaceae, yet we do not know why they are preferred. Contrast of white flowers attract these insects primarily, yet it is unknown if floral volatiles mediate host recognition. We observed a high abundance of A. verbasci adults on the umbels of Aegopodium podagraria and sought to determine whether this mass attraction is driven by floral volatiles. Gas chromatography coupled electroantennography, revealed 8 antennally active compounds from the headspace volatilome of A. podagraria. Y-tube assays confirmed that intact A. podagraria floral volatiles attracted A. verbasci adults significantly; however, this attraction was reduced when damaged umbels were presented. In Petri dish experiments, germacrene-D induced aversion, highlighting a possible repellency. Beetles seemed to prefer discs baited with A. podagraria headspace volatiles at first, yet choice shifted towards the visual stimulus of dried umbellets at the end of the experiments. We have concluded that olfaction plays an important role in host recognition of A. verbasci.