Carpenter ants are a widespread species of insect known for excavating wood to build extensive gallery systems for their colonies. While they do not consume wood like termites, the tunnels they carve can compromise the structural integrity of trees and homes. Like many insects in temperate climates, carpenter ants must develop a survival strategy to endure the cold temperatures and resource scarcity of winter. To sustain the entire colony, including the queen and developing brood, they rely on a complex physiological shutdown combined with a strategic retreat to insulated locations.
Entering the State of Diapause
As autumn temperatures drop and daylight hours shorten, carpenter ants enter a specialized physiological state called diapause. This period of dormancy, distinct from mammalian hibernation, pauses the insect’s development and activity. Environmental cues cause their metabolic rate to slow dramatically, allowing them to conserve energy reserves accumulated during warmer months, surviving on stored body fat and carbohydrates.
A preparation for the cold involves the production of a natural cryoprotectant within their bodies. Carpenter ants generate high concentrations of glycerol, an alcohol compound that functions similarly to antifreeze. This substance circulates in their hemolymph, or insect “blood,” lowering the freezing point of their internal fluids. Glycerol prevents the formation of ice crystals within tissues, protecting the ants from lethal cellular damage even if the surrounding temperature drops below freezing.
The production of glycerol is a temperature-dependent process, generated when temperatures fall close to the freezing point. During diapause, the queen ceases egg production, and the colony stops all nest expansion and foraging activities. The colony focuses on maintaining this low-energy, supercooled state until environmental conditions become favorable again. This metabolic slowdown is the species’ primary biological defense against the harsh winter environment.
Winter Nest Locations and Shelter
To complement their physiological changes, carpenter ants choose a physical location that provides maximum thermal stability throughout the winter. Outdoor colonies typically retreat deep into the core of their primary nest, often located in decaying logs, dead tree stumps, or buried wood. The density of the wood and the insulating properties of the surrounding soil buffer the nest from extreme temperature fluctuations.
They seek out locations that remain consistently above the freezing point, often below the frost line where soil temperature is more stable than air temperature. The ants seal off the entrances and exits of their galleries to maintain a stable microclimate within the nest chamber. Workers also cluster tightly around the queen and developing larvae to share body heat and maximize energy conservation.
When a colony establishes a satellite nest inside a heated human structure, the winter survival strategy changes completely. The warmth radiating from walls, attics, crawl spaces, or near water pipes is often sufficient to prevent the ants from entering full diapause. This means a colony nesting within a home’s wall void or insulation can remain active, albeit at a reduced pace, throughout the winter. If they find consistent warmth, they may continue to tunnel and forage inside the building, which is why they are sometimes seen indoors during the coldest months.
Reactivation and Spring Emergence
The end of winter is signaled by sustained changes in environmental conditions, specifically rising temperatures. As the ground and wood structures warm in the spring, this thermal increase acts as the trigger that breaks the diapause state. Unlike hibernating animals, which often follow an internal clock, the carpenter ant’s emergence is directly linked to these external temperature thresholds.
Once the dormant state ends, the colony quickly reactivates, and the queen resumes egg-laying to begin the reproduction cycle. The most noticeable initial activity is the emergence of winged reproductive ants, known as swarmers, in a process called the nuptial flight. These winged males and females leave the parent nest to mate and establish new colonies during the first warm, humid days of spring.
The returning warmth also increases the ants’ metabolic rate, prompting the workers to begin foraging for food and moisture to nourish the growing colony. The availability of new resources and the softened, moisture-damaged wood from melting snow and spring rains create ideal conditions for renewed colony expansion. This sudden burst of activity is often when homeowners first notice signs of an infestation.