4: The evolutionary divergence of wing shape across Bombycoidea reveals two distinct strategies for maneuverable flight

Wing shape can have profound effects on flight aerodynamics. To determine if distinct evolutionary groups adopt similar flight strategies, we examine how forewing shape and kinematics impact aerodynamic performance in two families, the hawkmoths (Sphingidae) and silkmoths (Saturniidae). Hawkmoths are known for their maneuverability and ability to hover during feeding; silkmoths do not feed as adults and display erratic flight. We find that the forewing shape of hawkmoths and silkmoths follow distinct evolutionary trajectories. Hawkmoths evolved short, high aspect ratio () forewings with high wing loading () and radius of the second moment of area (); all traits associated with low degrees of maneuverability. Conversely, silkmoths evolved larger, low  wings that exhibit low  and a smaller . As relationships between maneuverability and wing shape do not consider wing movement, we assess the aerodynamic consequences of the two distinct inter-clade wing shapes in an exemplar from each family (Saturniidae: Actias luna; Sphingidae: Eumorpha achemon). We find that flight performance results from the interactions of wing shape, size, and movement. Although hawkmoths employ forewing shapes unfavorable for maneuverability, we suggest that, in comparison to silkmoths, the evolution of high wing beat frequencies plays a significant role in flight control, allowing hawkmoths to complete high frequency maneuvers. Thus, divergence in forewing shape and movement between silkmoths and hawkmoths identifies two distinct strategies for agile flight. The complex interaction between wing shape and movement in flight performance might release morphological constraints, leading to the diversity of wing shapes across extant lineages.