Foraging rules for nectar: food choices by painted ladies.

Butterflies selected one of two contrasting locations for 10 visits without feeding followed by 16 visits with feeding. For each visit a location provided either 35% sucrose for 20 s versus 70% sucrose for 30 s or 35% sucrose for 20 s versus 70% sucrose for 20 s. These pairings tested between choices based on rates of net energy gain, net gains per visit, and/or net gains per meal. The first pairing produced choice based on maximizing net gain per meal. Choice for the second pairing was based either on maximizing net energy gain rate or net gain per visit. The change in foraging rule was associated with a change in volume per visit for 70% sucrose Understanding choices and the evolution of nectar rewards requires detailed information on alternatives, and interpretations of foraging behavior for nectar feeders should not be based solely on a criterion of maximizing net energy gain rate during foraging.