The density of cicadas cicada orni in mediterranean coastal habitats

Abstract

The aim of the study was to assess the use of sound level measurement as an index of cicada Cicada orni abundance in Mediterranean coastal habitats, to compare such measurements with indices of larval density at the same sites and to estimate the density of singing males. Sound levels were significantly higher in pinewood than in Mediterranean scrub and were intermediate in olive groves. There was a close correlation between sound level and the number of larval skins per tree, which explained 95% of the variation in sound. Measurements of the sound produced by individual cicadas (mean 97.43 dB at 1 cm) allowed an estimate, by computer simulation, of the density of singing males in July. Mean estimates of 9 861 males per hectare in pinewood and 1 618 in olive grove were obtained. The pinewood values were considerably lower than densities of final-instar larvae, measured in late May, but the discrepancy can be accounted for by larval and adult mortality in the period between the two sets of measurements. © 1997 Taylor & Francis Group, LLC.