The Multicolored Asian Lady Beetle (Coleoptera: Coccinellidae): Orientation to Aggregation Sites

Abstract

Several studies were conducted to determine the cues used by the lady beetle Harmonia axyridis (Pallas) when orienting to aggregation sites in autumn: (1) artificial shelters modeled after those commercially available in mail order catalogues were baited with live adults and hung on the outside of buildings known from past years to be aggregation sites, (2) differential arrival of the two sexes at overwintering sites was examined by collecting and sexing the beetles alighting on buildings at two points in time during the aggregation period, and (3) the distribution of overwintering H. axyridis among beehives was determined in ten apiaries. Results indicate no preference for the artificial shelters and no orientation to the conspecifics within them. Sex ratios of beetles arriving at aggregation sites were consistent over time in two of the three sites examined. During winter, adult H. axyridis were non-randomly distributed among physically similar beehives. We conclude that there is little evidence for volatile aggregation pheromones and suggest that the chemical cues that mediate the final stages of aggregation behavior in H. axyridis may be based on contact chemoreception with conspecifics or the feces and residues that persist in aggregation sites from previous years.