Demography, cold hardiness, and nutrient reserves of overwintering nests of the carpenter ant Camponotus pennsylvanicus (De Geer) (Hymenoptera: Formicidae)

Overwintering nests of C. pennsylvanicus were dissected and censused. All castes were assayed for glycerol and for changes in nutrient reserves. Spring queens were collected at swarming and allowed to initiate nests. Queens were analyzed for nutrient reserves during the early stages of nest founding.

Overwintering nests contained large proportions of larvae and alates. Physical associations within the winter nest were evident between majors and alates, and between larvae and the queen; minors were associated with larvae to a lesser degree. Reproductives and larvae were negatively correlated, and worker caste ratios shifted according to whether an area was dominated by larvae or alates.

Winter nest temperatures followed ambient temperatures, though fluctuations were less extreme. Glycerol was detectable in all castes and stages. Major and minor workers were similar in nutrient content. Lipid and protein contributed greater than 80% of dry weight, glycogen less than 20%, and free sugars less than 10%. Lipid was progressively depleted through winter. Majors lost most protein and dry weight between November and January, minors between February and April. Glycogen changes emulated mean ambient temperature patterns.

Overwintering gynes possessed large reserves of lipid, up to approximately 62% in mid-winter. Glycogen levels rose and fell with mean ambient temperatures.

Most nutrient reserves in founding queens were depleted from the head/thorax region between swarming and first larval emergence; between larval emergence and first worker eclosion, significant losses occurred only in the gaster. Protein alone increased significantly in the gaster prior to larval emergence, after which it was depleted.