The sampling scheme for root aphids in nest mounds of the ant Lasius flavus. a. A representative large aphid chamber with many, mostly adult, Geoica utricularia, b. Aphids were sampled from ant mounds on the island of Schiermonnikoog (The Netherlands) along a transect on the salt-marsh (framed area on map, corresponding to the area shown in Figure2). Sampling was done in a nested design with four levels. At every transect location (level 1, location 1–8), we sampled 5 ant mounds (level 2), by taking 21 soil samples (level 3), located in, on the edge of, or just outside an ant mound. The collected aphids within each sample were kept separate per aphid chamber (level 4). (Photo: A.B.F. Ivens, maps courtesy of D. Visser).