The butterfly rig, an Oceanic spritsail generally used tacking in a Melanesian world dominated by the shunting Oceanic lateen, is herein examined. The author goes back to original historical and ethnographical sources, particularly those of Layard from central Vanuatu in the early twentieth century, and uses this case to investigate the development of sailing technology in Oceania. It is argued here that although this rig resembles that of the reconstructed Lapita canoe as proposed by archaeologists, the butterfly sail may more convincingly be thought of as an Oceanic spritsail borrowed from Polynesia and adapted to the traditional shunting maneuver. The implications of such a scenario are important for our understanding of design, construction, and performances of ancient canoes. It is probably reasonable to think of Lapita sailors as shunting their lateen rigged outriggers while the Oceanic spritsail and its tacking maneuver were innovated farther east in Polynesia and later in time. In between these two schools of navigation, interaction and borrowing gave birth to a hybrid model: the butterfly sail.