Chemotactic responses of the ladybeetle Harmonia axyridis (Coleoptera: Coccinellidae) to volatile compounds from the scale insect Drosicha corpulenta (Hemiptera: Coccoidea: Monophlebidae) and its host plant

The ladybeetle Harmonia axyridis Pallas (Coleoptera: Coccinellidae), is a key predator of the scale insect Drosicha corpulenta (Kuwana), (Hemiptera: Coccoidea: Monophlebidae) in persimmon tree orchards. We used a Y-tube olfactometer and gas chromatograph/mass spectrometry to assess the possible role of volatiles from persimmon trees in attracting H. axyridis. The results showed more ladybeetles aggregated at odour sources from heavily damaged trees than from slightly damaged or undamaged trees. The relative amounts and types of terpenoid and alcohol compounds changed, usually increased, in the volatiles from damaged persimmon trees: α-pinene increased from 26 to 43%. The ladybeetle was attracted to α-pinene in a Y-tube assay at most tested concentrations.