The multicolored Asian lady beetle (Coleoptera : Coccinellidae): Orientation to aggregation sites

Several studies were conducted to determine the cues used by the lady beetl e 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 b uildings known from past years to be aggregation sites, (2) differential ar rival of the two sexes at overwintering sites was examined by collecting an d sexing the beetles alighting on buildings at two points in time during th e aggregation period, and (3) the distribution of overwintering H. axyridis among beehives was determined in ten apiaries. Results indicate no prefere nce for the artificial shelters and no orientation to the conspecifics with in them. Sex ratios of beetles arriving at aggregation sites were consisten t over time in two of the three sites examined. During winter, adult H. axy ridis were non-randomly distributed among physically similar beehives. We c onclude that there is little evidence for volatile aggregation pheromones a nd suggest that the chemical cues that mediate the final stages of aggregat ion behavior in H. axyridis may be based on contact chemoreception with con specifics or the feces and residues that persist in aggregation sites from previous years.