Carpenter bees resemble bumble bees. They are large, 3/4 to 1 inch long, heavy-bodied, blue-black to black colored with a green or purplish metallic sheen. Carpenter bees are solitary bees. That is, they do not live in a hive like honey bees. They do, however, tend to accumulate in certain areas.
Although technically wood-boring insects, they are not really considered a true structural pest. They will not spread throughout the structure, but they will utilize any outside wood that is not painted or finished. 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 1/4 inch in diameter. The hole is usually located on the underside of the wood surface, including siding, decks, overhangs, fence posts and window frames. Although the hole appears to be only an inch or two deep, it rarely ends there.
Along with the coarse frass (sawdust and insect droppings) 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 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.