Carpenter bees are large, solitary insects often recognized as a common pest due to their habit of boring into wooden structures. These bees resemble bumblebees but possess a smooth, shiny black abdomen, which distinguishes them from their hairier counterparts. They do not live in colonies like social bees but instead create individual nests within wood. The annual cycle of these wood-boring insects revolves around their survival through the colder months.
The Overwintering Process
When the weather turns cold, carpenter bees enter a period of dormancy, which allows them to survive the lack of nectar and pollen sources. This state of reduced metabolic activity conserves the energy reserves they accumulated during the warmer months. The bees do not migrate; instead, they remain sheltered within the wooden tunnels they or previous generations excavated during the nesting season.
The location for this long rest is typically an existing gallery within soft, untreated, or weathered wood, such as fascia boards, eaves, deck railings, or window sills. These tunnels, which can extend several feet along the wood grain, offer insulation and protection from freezing temperatures and predators. Within the gallery, the young adult bees that hatched the previous summer often cluster together in small groups for additional warmth.
They remain immobile and sealed off inside the wooden structure throughout the deepest part of winter, surviving on limited stored resources. The wood itself acts as a buffer against extreme thermal changes, keeping the interior of the tunnel relatively stable. The successful overwintering of these new adults is necessary for the continuation of the species into the next year.
Preparing for Winter
Preparation for winter begins in late summer, typically around August or September, when the new generation of adult carpenter bees emerges from their brood cells. These newly developed bees spend a few weeks foraging actively, feeding heavily on nectar and pollen to build up the necessary fat reserves. This energy is required to sustain them until the following spring.
As temperatures begin to consistently cool in the autumn, the bees seek out suitable wooden galleries for shelter. They often return to the same tunnels where they developed as larvae, or they may find new, abandoned nests. They locate a secure, dry cavity that offers sufficient thermal protection throughout the winter months. Before settling in, the bees may clean out or expand the entrance slightly.
The adult bees that survived the previous winter usually die off before this new generation begins its cycle of emergence and overwintering. Therefore, the young adults are responsible for carrying the species through the cold season. They enter their state of rest as mature insects, ready to resume activity as soon as environmental conditions are favorable.
Spring Emergence and Activity
The signal for carpenter bees to break their winter dormancy is the return of warm, sustained temperatures, which usually occurs in early spring, around March or April. Once the ambient air temperature consistently rises, the bees become active and begin to emerge from their wooden sanctuaries. Their first priority upon exiting the tunnels is to seek out sources of nectar to replenish their depleted energy stores.
Following this initial feeding period, the focus immediately shifts to reproduction and nesting. The surviving males and females mate, and the fertilized females then begin the search for appropriate nesting sites. Females will either bore a brand new, perfectly round entrance hole into unfinished wood or, more commonly, reuse and expand an existing tunnel. The males become highly visible during this time, aggressively patrolling the nesting areas to guard the females and deter rivals, though they are incapable of stinging.