Sexual dimorphism and allometric patterns in hawkmoth epiphyses (Lepidoptera: Sphingidae)

Sexual dimorphism in insects often extends beyond size differences, encompassing a range of morphological traits. These sex differences in wing size, body mass, antenna shape, and even the epiphyses of lepidopterans have been studied previously. The epiphysis, located on the foretibiae of lepidopterans, plays a crucial role in removing dust and other debris from the antennae, helping to maintain the sensory functions essential for navigation and communication. Unique to lepidopterans, the epiphysis is particularly important for species with highly developed antennae, such as hawkmoths. This study presents novel insights into the significant sexual dimorphism and allometric trends in the epiphyses of hawkmoths (Lepidoptera: Sphingidae). Through comprehensive morphometric analyses of 564 specimens across two tribes of Macroglossinae, we demonstrated that males typically possess longer epiphyses than females, correlating with antennal length. We observed that tibial length, epiphysis length, and width influence epiphysis positioning on the foretibiae. Our findings suggest that medium-sized epiphyses were a conserved trait in the common ancestor of extant hawkmoths, revealing both interspecific and intraspecific variations. This study not only advances the understanding of sexual dimorphism in lepidopterans but also sheds light on the evolutionary mechanisms driving morphological diversity. These discoveries contribute to a broader understanding of sexual dimorphism in Sphingidae and raise essential questions about the evolutionary pressures driving this variation in lepidopterans.