Carpenter bees are large bees which look very much like bumble bees, are excellent pollinators, and have the ability to hover in one spot. Each bee is an individual female, and they do not have a nest containing multiple individuals. When they emerge from their winter dormancy they go about their mating flights, and after mating, the males die, and the females start "drilling" holes in wood to use as a "nest". The hole is typically chewed from the back side of the wood, about 1/2 way through the wood, and then they turn at right angles and chew a hole about 6"- 8" long. Pollen and nectar from flowers is deposited in the holes, and an egg laid on the pollen. The cell is then closed with a plug of wood pulp, and another is laid until the entire tunnel is filled. After the "drilling" and egg laying is done the females die. In this part of the country, the Northesst, the reproductive cycle runs for about six weekd from late April until early June. The young develop over the summer and the adult bees emerge later in the summer and spend the rest of the summer foraging on flowers. There is only one reproductive cycle per year. The new bees hibernate for the winter in any protected spot and sometimes will return to the same tunnels they were born in for the winter. In the spring, the bees emerge and the cycle repeats itself. Unless the infestation is severe, the bees are more a nuisance and cosmetic problem than any stuctural one. They can be identified by sawdust on the ground ,or on another roof below the hole, and/or a yellowish brown fan-shaped dropping stain on the side of the building, just below their hole. A permanent solution to keeping them away is to replace infested boards with "Azek" or similar material that is the composite material used as decking.
Carpenter bee infestation
Carpenter bee tunnels
Carpenter bee dropping stain
Carpenter bee dropping stains below the holes drilled in the back of the rake board. The holes on the outside are from woodpeckers looking for the big, fat, juicy larve in the tunnels.