Population dynamics and life history of two Phaleria species (Coleoptera, Tenebrionidae) living on the Tyrrhenian sandy coast of central Italy

Two sympatric species of the genus Phaleria living on the beach of Burano (GR, Italy) were studied. Fortnightly samplings were made for a period of an entire year (from January to December 1996). Two transects of pitfall traps, spanning from mean sea level to the unvegetated limits of the beach, were arranged perpendicular and parallel to the shoreline so as to capture spontaneously active individuals. So as to better understand the life cycle of the Phaleria genus, another locality (Collelungo), where only Phaleria provincialis was present, was chosen. Samplings were fortnightly from January to December 1999. Sand patches of 0.25 m 2 were sieved every 2 m along a transect from mean sea level to the base of the dune. Organic detritus was collected and weighed in the laboratory. Through such a method, darkling beetles could be sampled during their resting phase so as to obtain information on their zonation. In the laboratory, all adults were dissected, sexed, ovarioles extracted and oocytes measured. For adults and larvae from Collelungo, morphometric measurements were made and larvae were classed. Annual distributions in both study localities indicated that the species are typically univoltine, with over-wintering adults and emergence of the new generation from summer to autumn. The life cycle of P. bimaculata was shifted in comparison to that of P. provincialis, showing greater eurythermal characteristics for the first species. Numerical differences in captures found between the two species are also discussed.