Landscapes and substrates with proliferating Caenorhabditis populations. The left panels depict landscapes in mainland France locations, as referenced in Table 1 and shown on the map on Figure 1. The central panels show examples of the corresponding sampled substrates that yielded Caenorhabditis. The right panels, except the bottom-most one, are Nomarski pictures of samples, showing a very heterogeneous composition, with bacteria, fungi and unidentified structures. A young Caenorhabditis juvenile is visible in the second panel from the top, labeled "Apple O151". The bottom panel is a juxtaposition of two focal planes of a large waving group of thousands of dauers, standing on rotten apple O673 (at the bottom of the picture). A few individual dauer larvae are indicated by arrowheads. The corresponding movie is available on request. Bars: 10 μm, unless otherwise indicated. On the Arum panel, the white arrow designates the rotting part of the stem. On the upperleft of the apple O831 panel, the small white animals are springtails.