A graphical interpretation of the increment-decay model for bumble bee patch departure. The conditional probability of landing on the next flower given the weighted stimuli sum

*z*,

*P*(Land

$\mid z$), is plotted as a function of time. The probability declines monotonically with time. If the bee finds nectar within a flower, the probability increases in proportion to the nectar volume. Solid circles represent reception of nectar, with the radius proportional to the nectar volume. Note that for the same amount of nectar the amount of incrementing is less in sequence, following (

4) in the text. When the threshold

${z}^{*}$ reaches its maximum value, it then spontaneously decreases, increasing the landing probability during interpatch travel (arrow).