Examples of coalescing colonies seen in the invasions of different species viewed at varying scales A conceptual representation of invasion via coalescing colonies B aerial photo showing Spartina alterniflora invasion into Willapa Bay, WA, (photo by Fritzi Grevstad) C spread of the gypsy moth, Lymantria dispar, in Ohio, USA. Interpolated pheromone trap captures from 2019 (data at http://yt.ento.vt.edu/da/) D spread of the emerald ash borer, Agrilus planipennis, in the eastern USA showing year of first discovery by county (data from USDA APHIS) E historical global spread of the Harlequin ladybird Harmonia axyridis (modified from Lombaert et al. 2010). Eastern North America has functioned as a bridgehead region from which colonization of other continents has originated.