These beetles bore through the bark and into the wood.

There they lay eggs.

The parent beetles soon die but their children continue the work of burrowing in the wood.
Finally, they kill the tree by making a complete cut around the trunk through the layers of wood that act as waiters to carry the food from the roots to the trunk, branches and leaves.

The next spring these young develop into full-grown beetles, and come out from the diseased tree.

They then attack new trees.
When the forest rangers find evidences of serious infection, they cut down the diseased trees.