Carpenter bees get their name from their ability to drill through wood and nest in the hole. Their drilling creates a near-perfect hole, approximately 1/2 inch in diameter. The hole is usually located on the underside of the wood surface; including siding, sofffits, decks, overhangs, fence posts and window frames. Although the hole appears to be only an inch or two deep, it rarely ends there.
The female carpenter bee will turn 90 degrees and bore a channel from 6 inches to as long as 4 feet. This channel serves as a main corridor from which she will drill small chambers a few inches deep. These chambers become egg holders. She will deposit an egg, bring in a mass of pollen for the newly hatched larvae to feed on, and then seal it all off to ensure it's development before she repeats the process for the next egg.
The male spends most of his time flying around the nest playing guard. This is ironic as nature has left him ill prepared: he has no stinger! Only the female can sting. Simply killing the male will not solve your problem. You must treat the nest.
Half-inch, round holes appear, and piles of sawdust are found underneath. Along with the coarse frass (sawdust) found underneath the nest entrance, there are usually dirty-yellow streaks of fecal matter staining the wood below the hole. If you are near a nest, you will likely be buzzed by the male carpenter bee on guard. He is loud and aggressive, but remember that he does not have the ability to sting you. The female can sting but she is normally very docile. A single pair (male and female) occupies each nest. It is not uncommon to find several pair of carpenter bees nesting in one structure. They frequently nest near each other and often in the same area year after year, causing extensive damage. You may find old holes near newer ones. Sometimes the female will renovate an old nest gallery and reuse it.
To control carpenter bees, do not concentrate on the adults. The annoying male bees are easy to kill with a wasp freeze such as PT515. However, killing the male will do nothing to stop the cycle. You must treat the nest with a product which will have a long residual killing time. If you spray liquid residuals in their hole, you may kill the female bee. The eggs are protected, however, and six to twelve months later the larva will emerge.