Life-time radio tracking of periodical cicadas detects minimal dispersal from emergence sites

Abstract The spatial distribution of periodical cicada ( Magicicada septendecim ) broods in the United States has remained relatively constant for two centuries, and the mechanism maintaining these sharply delimited, non-overlapping distributions is unresolved. It is unclear whether environmental factors constrain cicada dispersal, or whether individuals remain at their natal emergence sites by choice. We used micro-radio telemetry to follow 20 newly emerged teneral cicadas (10 male, 10 female; mean body mass 920 mg) throughout their entire adult life, together with five mating-plugged females. Flight tests showed that 300 mg transmitters altered, but did not constrain, aerial performance or propensity to fly. Only half of the individuals ever left their natal tree, and half of those returned to it. Over their whole adult life males moved a maximum (median) cumulative distance of 330 (0) m and virgin females 200 (20) m; mated females never exceeded 30 m. Virgin males lived 8.4 ± 1.4 SE days and virgin females 10.1 ± 0.9 days, and carcasses were recovered within 100 m of the tagging tree, most directly beneath it. Periodical cicadas can therefore disperse over substantial distances but do not. Stable brood distributions may require no active isolating mechanism, because adults scarcely reach brood boundaries.