Thermal responses of periodical cicadas: within and between brood parity (Hemiptera: Cicadidae: Magicicada spp.)

Abstract

Measurements of the thermal responses of insects have been used to determine thermal adaptation to various environments. We have compared the thermal responses (minimum flight temperature, maximum voluntary tolerance temperature, and heat torpor temperature) of five periodical cicada species (Magicicada septendecim, M. cassinii, M. septendecula, M. tredecassini, and M. neotredecim) to test the hypothesis that the thermal responses are similar within and between broods due to the similar environmental conditions experienced by each brood. Cicadas of Brood XIII were collected in 1973, 1990, and 2007 in northern Illinois. Comparisons are made to data from specimens collected during the 1987 Brood X and the 1998 Brood XIX emergences in southeastern Tennessee, and the 1989 Brood XXIII emergence in central Illinois. The maximum voluntary tolerance (an upper thermoregulatory temperature) and the heat torpor temperatures do not differ between the five species examined. Only one species (M. neotredecim) differs statistically in the minimum flight temperature from the other species and one species pair (M. septendecula and M. neotredecim) differs in heat torpor temperature. There were a few examples of between brood statistical differences in the minimum flight temperature (M. tredecassini) and heat torpor temperature (M. tredecassini, M. cassinii) and one species pair differed significantly in heat torpor temperature. The data show that thermal responses generally do not change statistically in different emergences of the same brood or over large portions of a species range and the thermal responses of all species are similar.