The evolution of two distinct strategies of moth flight

Across insects, wing shape and size have undergone dramatic divergence
even in closely related sister groups. However, we do not know how
morphology changes in tandem with kinematics to support body weight within
available power and how the specific force production patterns are linked
to differences in behavior. Hawkmoths and wild silkmoths are diverse
sister families with divergent wing morphology. Using 3d kinematics and
quasi-steady aerodynamic modeling, we compare the aerodynamics and the
contributions of wing shape, size, and kinematics in 10 moth species. We
find that wing movement also diverges between the clades and underlies two
distinct strategies for flight. Hawkmoths use wing kinematics, especially
high frequencies, to enhance force, and wing morphologies that reduces
power. Silkmoths use wing morphology to enhance force, and slow, high
amplitude wingstrokes to reduce power. Both strategies converge on similar
aerodynamic power and can support similar body mass ranges. However,
inter-clade within-wingstroke force profiles are quite different and
linked to the hovering flight of hawkmoths and the bobbing flight of
silkmoths. These two moth groups fly more like other, distantly related
insects than they do each other, demonstrating the diversity of flapping
flight evolution and a rich bio-inspired design space for robotic
flappers.