EN
Observations on the biology of Pediacus depressus (H ERBST, 1797) were carried out between years 2017 and 2019. Notes on the species biology and ecology are discussed. Development takes place in still fresh, broken trunks and boughs of deciduous trees: oaks Quercus spp., beeches Fagus spp., alders Alnus spp., willows Salix spp. and the Norway maple Acer platanoides L. Both larvae and adults are feeding on sap of broken boughs and fallen trees. Mature larvae were found in December under the bark of broken bough of relatively fresh bark of A. platanoides with still many leaves covering the branches.The abundance of the sap and dried leaves signifies that ovipositing must have taken place right after the adults hatched and mated. Adults from collected larvae emerged in January, which usually takes place at the turn of May and June in nature. This indicates that whole life cycle lasts around a year. A. platanoides turnes out as new host plant for the species larvae. For the first time, two new localities were reported in forest nature reserves in Warsaw: Bielany and Natolin. These are at the same time second and third localities from Mazovian Lowland after decade, respectively.