Figure 1.

A map showing the geographic location of the sampling sites of calochroid population samples across Europe, North America and Central America. Population samples of C. arcuatorum are represented in blue, C. aureofulvus in orange, C. elegantior in red and C. napus in green. Collection numbers correspond to collections in Additional File 4. Distribution of host plant families: green dashed lines indicate distribution of Fagaceae and red dashed lines indicate distribution of Pinaceae, respectively.