Emergence of 13‐Yr Periodical Cicadas (Cicadidae: Magicicada): Phenology, Mortality, and Predators Satiation

Abstract

We examined emergence of male and female 13—yr periodical cicadas (Brood XIX) and mortality, due to avain predation, fungal infection (Massospora cicadina), environmental factors, and senescence. We compared relative contributions of the sources of mortality, and determined the temporal pattern of avian predation associated with predator satiation and mortality. Based on a mean density of 6.65 emergence holes/m2, we estimated that 1 063 300 cicadas emerged on our 16—ha study area in northwestern Arkansas during May 1985. Males appeared first in emergence traps in early May and emerged more synchronously than did females. About 50% of the population emerged during four consecutive nights, and peak abundance of adult cicadas occurred in late May. Based on samples from mortality traps, at least 40% of the population died in severe thunderstorms during the first week of June, demonstrating the stochastic factors can be major influences on periodical cicada populations. Fungal infection was not a major source of mortality. The first cicadas that emerged in early May were eaten by birds, but avian predators became satiated. Birds consumed 15—40% of the standing crop at low cicada densities, but very little of the standing crop was consumed when cicada densities were >24 000 individuals/ha on the study site. Avian predators appeared to be satiated for several weeks, and by the time their foraging activities increased due to demands imposed by feeding young, density of adult cicadas was relatively low. Mortality due to predation gradually increased to near 100% as the density of adult cicadas declined in June. Based on estimates of cicada emergence and deaths due to avian predation where adult cicada activity was greatest, birds consumed only °15% of the adult cicada population. Therefore, only a small proportion of the adult cicada population was actually consumed by avian predators. These results demonstrate that, indeed, the synchronized, explosive emergences of periodical cicadas may be classical examples of predator satiation.