Fig. 7. The threshold for pymetrozine action on the femoral chordotonal organ is 10^–8 mol l^–1. Response of the middle leg femoral chordotonal organ (fCO) was monitored during ramp-and-hold stimulation of the receptor apodeme [ordinate; spike counts during elongation (filled circles) and relaxation (filled squares) ramps, baseline activity subtracted]. Different concentrations of pymetrozine were applied, starting with 10^–9 mol l^–1 and increasing in steps of 5-fold or 2-fold (abscissa) every 25 min until stimulus-related responses had completely vanished. 10^–5 mol l^–1 was applied as the final control concentration. Numbers of measurements per data point (n=N) range from 6 (above-threshold concentrations) to 12 (threshold area). Median values and 25% percentiles are shown. Graph for relaxation stimuli is offset to the right by 20% for better visibility of percentiles. Note that calculation of medians from data obtained in several individuals obscures the fact that in any given animal pymetrozine had an all-or-none effect, although at slightly different concentrations; for details, see text.