We measured wingtip speed, as an indicator of angular velocity, during the single downstroke that lifts butterflies and moths from the ground to flight. High‐speed analysis captured 745 takeoff events across 131 lepidopteran species. Wingtip speed showed no correlation with forewing length, a proxy for the Reynolds number and wingtip speed. In contrast, wing loading ( ŵ , Nm −2 ) correlated strongly with wingtip speed (U, ms −1 ) (correlation coefficient = 0.76, R 2 = 0.57), following lnU = 0.442 + 0.261∙ŵ – 0.015∙ŵ 2 . Using this relationship in quasi‐steady element blade theory predicts peak lift forces that are 3–6 times the weight of the butterflies and moths. We also present evidence that wing loading determined wingtip speed may be valid for any lift‐generating downstroke. Biologically, this indicates that butterflies and moths of widely varying size and mass achieve precisely tuned lift force by modulating wingtip speed during the initial downstroke.
Terland et al. (Thu,) studied this question.