Carpenter bees are large, solitary insects often noticed for their attraction to wooden structures, despite being important native pollinators. Understanding what draws them in is the first step toward protecting wooden components of a home or property. Their attraction is twofold: the need for a protected nesting site and the constant requirement for nectar and pollen as a food source. The factors that attract a carpenter bee are highly specific, ranging from the condition of wood to environmental cues like existing tunnels.
Preference for Specific Wood Types
The primary attraction for a female carpenter bee is wood suitable for excavating a nest, as they do not consume the material. Using strong mandibles, they bore a circular entrance hole into the wood surface and tunnel parallel to the grain to create a gallery where they lay eggs and provision food. This nesting activity is why they are considered pests to wooden structures.
Carpenter bees exhibit a strong preference for softwoods like pine, cedar, redwood, and cypress, as these are easier to bore into than hardwoods. They are particularly attracted to wood that is bare, weathered, or untreated, which signals a less dense and more accessible material. Paint, varnish, or a solid topcoat acts as a significant deterrent, making these surfaces far less susceptible to attack. Stained wood offers less protection than a fully painted surface but is less attractive than bare wood.
Common targets for nesting include exposed structural elements like fascia boards, eaves, soffits, and the underside of decks and railings. These locations offer accessible wood combined with shelter from rain and predators. The female bee often seeks out the end-grain or existing cracks and nail holes, which provide a head start on excavation. Continued activity in the same location year after year can lead to extensive tunnel networks, compromising the wood’s integrity.
Attraction to Nectar and Pollen
While they bore into wood for shelter, carpenter bees are primarily attracted to flowering plants for sustenance. They feed on nectar for energy and collect pollen for protein, acting as generalist foragers across a wide variety of plants. The female bee mixes the collected nectar and pollen to create “bee bread,” which she places in the nesting chambers to feed her developing larvae.
Carpenter bees are effective pollinators due to their large size and method of “buzz pollination.” However, they are also known for “nectar robbing,” particularly on flowers with long, deep corollas. If the bee cannot easily reach the nectar, it uses its mandibles to slice a small hole near the base of the bloom. This allows the bee to access the nectar without entering the flower, bypassing the reproductive parts and avoiding pollination.
This foraging need means that homes with well-maintained flower beds, especially those close to wooden structures, may experience a higher presence of carpenter bees. The bees are drawn to the food source and then seek out the nearest suitable nesting site. Their strong attraction to sugar means sugar water can be used as a successful bait in specialized carpenter bee traps.
Visual and Environmental Signals
Carpenter bees are highly influenced by visual and environmental cues that signal a suitable nesting location, beyond the physical properties of the wood itself. One of the strongest attractants is the presence of existing bore holes or old galleries. A female bee prefers to reuse or expand an existing tunnel, as this requires significantly less energy than excavating a new one.
This preference is reinforced by chemical signals, as female carpenter bees leave behind pheromones that attract subsequent generations. These pheromones cause bees to return to the same general area year after year. The visual appearance of a hole, even a small crack or splinter, offers a physical starting point for a new tunnel.
Carpenter bees can be attracted to certain colors, especially bright colors like blue, which mimic the appearance of flowers from a distance. Traps designed to capture these bees often incorporate this color to increase effectiveness. Furthermore, the bees tend to select locations protected from the elements, such as eaves or the underside of railings, which offer a naturally sheltered and dry environment for their offspring to develop.