Bombycoid moths: an emerging model clade for studying insect flight

Flying insects achieve extraordinary locomotor performance through diverse combinations of physiological, morphological, and mechanical traits, exemplifying the many-to-one mapping between biological components and emergent flight behavior. Here, we argue that the moth superfamily Bombycoidea is a tractable and compelling emerging model clade that facilitates integration between controlled experimentation and phylogenetically informed comparative analyses, complementing single-species studies to understand the evolution of insect flight. Bombycoidea is a monophyletic group with a well-resolved phylogeny that includes approximately 6,000 described species in 10 families distributed globally. Bombycoidea includes the hawkmoths (Sphingidae) and wild silkmoths (Saturniidae), which are known for their contrasting life history and flight behavioral strategies. Most hawkmoths perform agile hover feeding behavior, while silkmoths display erratic flight behavior and do not feed as adults, limiting the silkmoth energy budget. Hawkmoths and silkmoths perform divergent flight behaviors using different combinations of wing shape, size, and kinematics. In addition to the stark divergence in flight behavior and related traits, hawkmoths and silkmoths have extensive interspecific variation, including multiple examples of convergent evolution in life history (e.g. loss of functional adult mouth parts), wing morphologies (e.g. hindwing tails), and wing patterning (e.g. hindwing spots) that occur both within and between these two families and across other bombycoid families. Hawkmoths also include the Tobacco hornworm (Manduca sexta), and extensive research on flight in this species provides a foundation needed for comparison across Bombycoidea. These features of Bombycoidea, in addition to the recent advancements in technology, enable a tractable avenue for large-scale comparative work at unprecedented scales and resolution. Finally, we highlight recent advances in insect flight research using bombycoid moths and outline how this clade can inform future studies aimed at uncovering general principles of insect flight, animal behavior, and locomotion.