Figure 2. Flight performance of eastern and western North American monarchs. Butterflies were collected from St. Marks, a stopover of eastern monarchs on their way to Mexico, and Pismo Beach near Oceano, an overwintering site of western monarchs in California. Butterflies were placed on a tethered flight mill (A), and flight time (B), distance (C), and power were recorded during standardized flight trials. Data points show individual butterflies, while horizontal lines indicate means. Eastern butterflies flew significantly longer (P=0.004) and greater distances (P=0.04) than eastern monarchs, while western monarchs had higher powered flight (P=0.02).