Figure 2. Visualization of a pheromone plume.

The figure is extracted and adapted from a digitized image of a smoke plume filmed in a wind tunnel 1 m across and 2 m long with source on the left side [43]. Though the average pheromone concentration in the air decreases with distance, high pheromone concentrations can be found relatively far from the source due to the imperfect mixing of odorant with air. The signal detected by both moving and stationary detectors is therefore always intermittent, consisting of pulses of relatively undiluted pheromone.