D3563: Structural overview of the trochanteral gear morphotypes of nymphal Fulgoromorpha

Planthoppers (Hemiptera: Fulgoromorpha) are the only animals known to have functional gear mechanisms. The gears are located on the hind trochantera of nymphs and ensure synchronous movement of the legs during a jump. Thus far, description of these mechanisms has been incomplete and limited to a few species. In this study, we describe the gear mechanisms of 15 species, conduct principal component analysis on quantitative data collected from scanning electron micrographs, and examine differences in gear morphology in the context of molecular phylogeny. The gears of Delphacoidea and early Fulgoroidea contain long narrow teeth while more derived Fulgoroidea have curved and sometimes triangular teeth. Our findings demonstrate morphological support for the relationships proposed by molecular phylogeny. The angle between the end teeth and the ventral coxo-trochanteral pivot and the degree of rotation per tooth differ significantly by dominant tooth shape. During a jump, the distance from the pivot to the root of the tooth increases as the tooth depth decreases. Future investigation of the nymphal planthopper jumping apparatus and the mechanical effects of the observed varying gear morphology could inform the evolution of these structures and promote bioinspired engineering applications.