THE DENSITY OF CICADAS CICADA-ORNI IN MEDITERRANEAN COASTAL HABITATS

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 h abitats, to compare such measurements with indices of larval density a t the same sites and to estimate the density of singing males. Sound l evels were significantly higher in pinewood than in Mediterranean scru b and were intermediate in olive groves. There was a close correlation between sound level and the number of larval skins per tree, which ex plained 95% of the variation in sound. Measurements of the sound produ ced 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 g rove were obtained. The pinewood values were considerably lower than d ensities of final-instar larvae, measured in late May, bur the discrep ancy can be accounted for by larval and adult mortality in the period between the two sets of measurements.