Geographic locations of the sampled populations of H. axyridis. Note: (A) Geographical regions of the different native (Z1 and Z2) and invasive (X1 to X3 and Y1 to Y3) sampled populations of H. axyridis. Closed circles correspond to locations where the two native populations have been sampled. (B) The Western European invasive populations of H. axyridis were sampled along two transects. Letters (X or Y) correspond to the transect names, and years are the dates of the first observation of H. axyridis at the sampled geographic localities. Two biocontrol populations reared in European laboratories since 1981, probably originating from China, were also used for the present study. See main text for details.