FIGURE 1. Typical infotactic trajectories.

a, Without wind; b, with wind. Simulations are performed for a model of odour spreading where detectable 'particles' are emitted at rate R, have a lifetime , propagate with diffusivity D (combining turbulent and molecular diffusion) and are advected by a mean wind V. The wind in b is directed downwards. The greyscale represents the mean detection rate, decaying exponentially at large distances. In each panel, the searcher starts from the black filled triangle, the colour code on the trajectories is linear in the elapsed time, and odour detections are indicated by black filled circles. Note the long lags with no particle detections, characteristic of searches in dilute conditions.