There are several different species of carpenter bees, but the most common one looks like a bumble bee. This bee is unique because it bores into wood and, over time, does considerable damage. They also bother homeowners and innocent passers-by with their diving “attacks.”
Carpenter bees will bore into practically any wood including (but not limited to) overhangs, fascia boards, decks, fences, siding, sills, doors, etc. Wood and cedar sided houses and barns are particularly vulnerable to carpenter bee damage. They bore a hole about .5″ diameter. This hole will go straight into the wood about 1-2 inches, turn 90 degrees, and then proceed to excavate a chamber. This chamber can be anywhere from 5-6 inches deep to 2 feet deep with branching chambers generally aligned with the grain of the wood. They lay a single egg at the end of each chamber. Food is placed into the chamber with the egg and the chamber is sealed.
Females guard the nests aggressively. Males are curious. Both of these behaviors account for the “dive bomb attacks.” The eggs hatch into larvae. The larvae feeds on the food then metamorphoses into an adult Carpenter bee which then exits the hole. This new generation of bees tends to make their homes in the same area as their parents. A single nest one year will be 2 or 3 the next. A few years of unchecked activity can lead to literally hundreds of holes, lots of bees, and considerable damage.