The Presence and Distribution of Transition Metals and Other Inorganic Elements in the Cuticle of Cicadas (Hemiptera: Cicadidae)

Cicadas (Cicadidae: Hemiptera) are one of the most popular groups of insects. The loud mating calls of male cicadas and the mass emergence of 13- and 17-year periodical cicada lineages in North America have created several newsworthy stories that reveal their uniqueness. The life history of cicadas includes using piercing structures, such as mouthparts and ovipositors, to pierce through bark to feed on xylem and for egg deposition, respectively. Due to these behaviors, we previously explored the elemental composition of the cuticle of mouthparts and ovipositors from four cicada species and found that both structures have transition metals present in their distal regions, which increase cuticular hardness and facilitate the piercing process. Here, we further explored the presence, distribution, and concentration of inorganic elements in the cuticle of cicadas on other structures and body locations, including the tarsi and femur of the forelegs and dorsal regions of the pro- and mesothorax and abdomen. We combine these new results with previously published results to better understand elemental patterns of the cicada cuticle and how they might be adaptive. In general, we found that cicada species differ in the elemental composition of their cuticle and that transition metals also are present in nonpiercing structures. We also observed that elements grouped similarly (e.g., transition metals, nonmetals, alkaline Earth metals, etc.) do not have similar patterns in how they are represented in the cuticle, suggesting that elements with similar chemistries might have different effects on the mechanical properties of the cuticle.