Characterization of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) overwintering sites

The invasive multicoloured Asian ladybird, Harmonia axyridis (Pallas), forms large aggregations inside dwellings to overwinter. In order to highlight the specific features of infested houses, we investigated a large number of overwintering sites in Wallonia between 2007 and 2011. These sites were characterized through a survey sent to homeowners confronted to invasion problems. The results indicate that H. axyridis preferentially selects isolated brick houses with red or white fronts to take shelter. Aggregations are mostly located at the first floor, essentially inside south or west oriented rooms. Furthermore, ladybirds generally gathered into wooden windows frames facing south or west, and to a lesser extent, in the upper corners of walls presenting the same orientation.