Flight period of Gasterocercus depressirostris in relation to temperature in North-eastern Italy

Gasterocercus depressirostris (F.) (Coleoptera Curculionidae) is a rare species found in European “Querco-Carpinetum” primary forests. From the literature of Central Europe it is known that the larvae live in trunks of dying oak and beech trees, and the adults fly from June to September. In some natural woodlands in the Friuli Venezia Giulia region (North-eastern Italy), trunk window traps were placed to monitor weevil phenology by the capture of adult insects during flight. A relationship was established between capture numbers and temperature by use of the Day Degrees (DD) method, with the aim of acquiring data on the flight period of this species and the use of DD as an estimator of this aspect of G. depressirostris phenology. The insect flight was observed from the end of May to the end of July and for its flight to occur, approximately 750 DD and an average minimum temperature above 15 °C were necessary.