(Because of the higher-than-usual number of bees this season and the resulting questions about them, we are reprinting this post that originally appear in March, 2015)
March usually brings the first sightings of carpenter bees in north Florida. Carpenter bees are large, black and yellow bees often seen hovering around the eaves of a house, wooden fences or decks on warm days. They may be mistaken for bumble bees but differ in that they have a black shiny abdomen in contrast to the yellow abdomen of the bumble bee.
Richard Sprenkel, retired UF/IFAS Entomologist, shares information about this wood boring bee in today’s article.
Carpenter bees spend the winter as adults within their old nest tunnels. After emerging in spring, adults mate and females begin excavating a gallery with their mandibles (mouthparts) at the rate of one inch in six days. The gallery has a clean-cut, round entrance hole approximately ½ inch in diameter. The gallery continues inward for one to two inches, and then turns at a ninety-degree angle running in the same direction as the wood grain for four to six inches. Damage from a pair of bees is slight but if the gallery is used over several years, damage can be extensive.
Once a gallery is completed, the female begins to provision a brood cell with a mixture of pollen and regurgitated nectar. After laying an egg on top of this mass, the female closes the cell with chewed wood pulp. Each female may have six to eight sealed brood cells in a linear row in one gallery as she backs outward. Larvae develop on the pollen/nectar food. The lifecycle is completed in thirty to forty days.
Newly developed adults emerge by chewing through the cell partitions. They collect and store pollen in existing galleries, which they use for winter hibernation. There is one generation per year. Males do not drill tunnels but are territorial and harass other bees and people who come near their protected areas.
Males do not sting and can be distinguished from females by a whitish spot on the front of their face. Females are capable of stinging but rarely do so unless they are highly agitated or confined in your hand.
Carpenter bees prefer wood that is bare, weathered and unpainted. The best way to deter the bees is to paint all exposed wood surfaces, especially those that have a history of being attacked. Wood stains and preservatives are less reliable than painting.
Preventive sprays applied to wood surfaces are effective only for a short period and would have to be repeated about every two to three weeks. However, once nesting activity has begun, treating the entrance holes with an insecticidal spray or dust may substantially reduce damage. Products containing carbaryl (Sevin), cyfluthrin or resmethrin are suitable.