Last week I got a peek at where Camponotus pennsylvanicus carpenter ants spend the winter.
The temperatures were hovering around freezing in upstate New York, where I was helping someone spit firewood.
When the wood split, occasionally we would find tunnels, hardly more than grooves in the wood, packed with ants. Although the ants look like they might have been moving, they were mostly stiff and inactive. You could shake them out onto the ground without much resistance.
This group was in softer wood with more decay. Notice the larva. Most of the clusters of worker ants had small larvae with them.
Camponotus carpenter ants that live in temperate climates enter a state of slowed metabolism, called “diapause”, in the late fall and through the cold parts of the winter. Generally, the queen stops laying eggs. The workers begin to aggregate more than before. The workers develop large fat bodies, which can be seen as their gasters swell in size, as well as produce glycerol. Glycerol is an alcohol that helps prevent the formation of ice crystals within the ants’ bodies. No wonder the ants stagger a bit when they try to move. 
What are ants doing this month where you live?
For more information try:
Cannon, C. A. 1990. Demography, cold hardiness, and nutrient reserves of overwintering nests of the carpenter ant, Camponotus pennsylvanicus (De Geer). M. S. Thesis, Virginia Polytechnic Institute and State University. 165 pp.
Cannon, C.A. and R.D. Fell. 1992. Cold hardiness of the overwintering black carpenter ant. Physiol. Entomol. 17:121-126.
