Convergent evolution of antipredatory bioacoustic traits in bombycoid moths (Lepidoptera: Saturniidae, Sphingidae)

Moths have evolved an astonishing array of antipredatory traits ranging from the sequestration of defensive toxins to deimatic displays. Within the Bombycoidea, many silkmoths (Saturniidae) and hawkmoths (Sphingidae) employ disparate yet effective bioacoustic tactics to thwart bat attacks. Among Saturniidae, several lineages have independently evolved elongated hind wings with twisted tails that lure bat strikes away from vital body parts. Concordantly, numerous Sphingidae facilitate their escape by producing ultrasound that is capable of disrupting echolocating bats. Despite these being relatively high-profile features well known among lepidopterists, detailed investigations into the three-dimensional morphology and microsculpturing underlying these traits have been lacking. Herein, using microtomography (microCT) and Scanning Electron Microscopy (SEM), we examine the complex 3D shapes and scale morphologies that putatively enable silkmoths to create decoy echoes that confuse bats. Similarly, we survey the diversity of ultrasound producing stridulatory structures in male hawkmoths where modified genital scales (the scraper) rub against modified scales, spines, or microsculpturing on the ventral surface of the last abdominal tergite (the file). In both groups, we investigate these traits in a phylogenetic context and demonstrate their tendencies to coalesce on adaptive optima. Our findings ultimately provide novel insights into the iconic bat-moth arms race.