Periodical cicada (Homoptera: Cicadidae) life-cycle variations, the historical emergence record, and the geographic stability of brood distributions

Abstract

The complex biogeography of the 13- and 17-yr periodical cicadas offers important opportunities for testing hypotheses of Magicicada evolution and ecology. However, misinterpretation of stragglers as on-schedule emergences, combined with systematic biases in search effort and the use of cross-generational brood maps, likely results in erroneous edge extension of adjacent broods and the appearance of sympatric shadow broods in published maps. Substantial recent changes in brood distributions have been inferred from the Magicicada historical record, the most significant being the decline and extinction of 17-yr brood X in the midwestern United States, the widespread expansion and contraction of 17-yrbrood VI and 13-yr brood XXIII, and the displacement of brood XIII 17-yr cicadas in Illinois by 13-yr brood XIX in Illinois. Reanalysis of the historical data with an awareness of straggler-induced error suggests instead that brood distributions in these cases have remained stable. © 2001 Entomological Society of America.