Butterflies present a stunning diversity of wing size and shape, yet the evolutionary drivers of this diversity are poorly known. In particular, many species harbour tails on their hindwings, differing in number, length and shape. Surprisingly, little is known about the selective forces affecting their evolution. Here we explore the hypothesis that tails might contribute to flight performance, which might influence fitness, since flight is involved in escape, patrolling and foraging in butterflies. Here we focus on a genus of fast flying paleotropical butterflies,Charaxes, displaying a high diversity of wing shapes, including species with no tail, one pair of tails, or two pairs of tails. We compared the flight of 20 morphologically diverse and sympatricCharaxesspecies in central Côte d'Ivoire, using stereographic videography in semi natural conditions (an outdoor flight insectary). We filmed several individuals from each species (leading to a total of 230 individual flights) with high speed cameras (120 frames per second), and reconstructed their 3D flight trajectories using a custom tracking tool. We then extracted flight variables to quantify the variation in flight behaviour across species. We are now using phylogenetic comparative analyses to assess how flight parameters correlate with morphology, including mass, wing loading and wing shape quantified through geometric morphometrics. By contrasting tailed and tailless species, we aim at identifying the effect of wing tails on flight, allowing to better understand the drivers of their morphological evolution, and contribute unraveling the link between wing morphology and flight performance.