Under mass breeding conditions, European cockchafers, Melolontha melolontha L., may defoliate entire forest stretches. However, losses in agriculture and horticulture caused by the root feeding larvae, the so called white grubs, are economically even more important. To promote fundamental chemo-ecological understanding as well as environmental sound means of pest control, chemical orientation and communication has been investigated in the course of this thesis, both in adults above and larvae below ground.