Confusion between large, fuzzy bees is common, especially when signs of wood damage appear near a home. Many people observe a bee resembling a large bumble bee hovering near wooden structures and assume they are the same species responsible for drilling holes. This article clarifies the specific behaviors of these insects to accurately identify the culprit behind wood boring activity.
The Direct Answer: Bumble Bees Do Not Burrow in Wood
Bumble bees, belonging to the genus Bombus, do not bore into cured lumber or wooden structures. They are not considered structural pests and do not excavate their own tunnels into solid wood. When a large, fuzzy, yellow and black bee is seen near a deck or fascia board, the concern about wood damage is understandable, but it is almost certainly a case of mistaken identity. The true wood-boring insect is a different species entirely, though it is often visually similar.
The Actual Nesting Habits of Bumble Bees
Bumble bees are social insects that establish colonies, but they are not excavators of hard material. A newly emerged queen searches for a pre-existing, insulated cavity to begin her nest, typically utilizing sheltered spaces created by other animals or natural processes. Common nesting sites include abandoned rodent burrows, dense clumps of grass, or voids under sheds and stone piles. They utilize these spaces because they lack the strong mandibles required to chew through wood or dig deep tunnels in hard soil. Their construction efforts are limited to lining the cavity with wax pots for storage and laying eggs.
Identifying the True Wood-Boring Culprit: Carpenter Bees
The insect responsible for the perfectly circular holes found in wooden structures is the carpenter bee, primarily belonging to the genus Xylocopa. Female carpenter bees use their powerful mouthparts to drill into wood, creating galleries where they will lay their eggs. They show a strong preference for soft, unpainted, or weathered wood like cedar, redwood, cypress, and pine, often targeting eaves, fascia boards, and deck railings.
Signs of Carpenter Bee Damage
The signature sign of their activity is a nearly perfect, half-inch diameter entrance hole that appears as if a drill bit was used. This hole penetrates the wood surface for a short distance before making a sharp right-angle turn to run parallel with the grain, forming a gallery that can extend six to eight inches. As the female chews, she expels a sawdust-like material mixed with wood fragments, known as frass, which often accumulates in a small pile directly below the entrance hole. The female then divides this tunnel into several individual cells, provisioning each with a ball of pollen and a single egg before sealing it off with chewed wood pulp.
Visual Differences Between Bumble Bees and Carpenter Bees
Telling the difference between the two species requires focusing on a single, reliable physical characteristic: the abdomen. Bumble bees have dense, fuzzy hair covering their entire body, including the abdomen, which gives them a distinctly rounded, teddy bear-like appearance. Their abdomen is usually banded with yellow and black hair.
In stark contrast, the carpenter bee has a smooth, shiny, black abdomen that is mostly hairless and often appears polished or metallic. While the carpenter bee’s middle section, the thorax, is often covered in yellow fuzz, the polished appearance of the rear section is the definitive indicator. Observing this difference is the fastest way to determine if the bee is a beneficial pollinator or a wood-boring insect.