When full-grown, typically in one to two years, the adult stages cut a hole through the bark and emerge. Many of the adult borers, particularly the longhorned beetles and metallic wood borers, feed on pollen, tender bark or leaves but do not cause any significant injury. The adult stage is mostly spent flying to new host trees, mating and laying eggs. Eggs of most shade tree borers are laid on the bark, usually within small cracks. Longhorned beetles and horntails deposit their eggs underneath bark.
Eggs typically hatch within one to two weeks, and the newly emerged borers chew through the bark.
Subsequent borer development takes place just under the bark and in the wood. As the borers tunnel in the tree, they make meandering tracks that are packed with fibrous boring dust. When fully developed, the adult insect emerges through a hole chewed in the bark. With the exception of horntails, these exit holes are oval. Longhorned beetles are named for the very long antennae typical of the adult.