Fig 5. Schematic sketches for the number of successes s and s_p expected for a WF wasp and PF wasp to complete in one foraging cycle respectively when the common stomach water level is w.

The established average water level of the common stomach is $\overline{w}$ (arrow), and it is assumed to have a value greater than where max(s_p) occurs and has a value less than w = 0.5. The empirical average numbers of successes [26] for a WF wasp and PF wasp (5.2 and 6.4 respectively) occur at water levels greater and less than the average $\overline{w}$ respectively (this is deduced from the hypothesized shapes of the curves). Note that s = 5.2 might occur below, at, or above w = 0.5. Also, s_p = 6.4 occurs at a water level nearer to the average $\overline{w}$ than does s = 5.2. Note that $\overline{w}$ is located under a steeper section of y = s_p(w) than of y = s(w), so that the deviation in s_p is greater than the deviation in s (4.3 > 2.8) in agreement with empirical findings of Karsai and Wenzel [26].