Stag beetle appear in early summer. What is interesting, before that, the larva of the stag beetle develops for a very long time - on average 5 years. Usually in a rotten oak stump, or in rotten tree roots. Beetles feed on sap released from cracks in trees, usually oaks. Several beetles often collide at such a feeding place and the strongest throws the enemy off the tree, similar fights take place for the female.