Carpenter ants (Camponotus) are often confusing regarding their size. While the species includes some smaller workers, the genus is generally recognized for containing some of the largest ants in North America. The size of a carpenter ant varies significantly based on its role within the colony, a phenomenon known as polymorphism. Even the smaller carpenter ants are noticeably large compared to many common household species.
The Wide Range of Carpenter Ant Sizes
The size of a carpenter ant is determined by its caste, or social role within the colony structure. This polymorphism results in a wide range of body lengths, with workers categorized as minor, media, or major. Minor workers, the smallest, measure about 6 millimeters (one-quarter of an inch).
Major workers are substantially larger, often reaching 12 or 13 millimeters (about half an inch). The largest individuals are the queens, who can measure up to 20 millimeters (nearly one inch). This size difference facilitates a division of labor, where larger major workers defend the colony or crush seeds, while smaller workers tend to the young.
Distinct Physical Traits Beyond Size
Since size is variable, proper identification relies on observing the unique physical structure, or morphology, of the ant’s body. A defining characteristic is the smoothly rounded, arched profile of its thorax, the middle section of the body. When viewed from the side, the dorsal profile of the thorax is a continuous, convex curve, lacking the indentations or dips found in many other ant species.
Another distinguishing feature is the petiole, the single, upright segment connecting the thorax and the abdomen. This single-node waist contrasts with other ant types that have two distinct nodes. Furthermore, the antennae are distinctly bent, or “elbowed,” at an approximate 45-degree angle.
Confusing Carpenter Ants with Termites and Other Ants
Carpenter ants are frequently mistaken for other pests, particularly during the swarming season when winged reproductive individuals emerge. Distinguishing a winged carpenter ant from a termite swarmer requires close inspection of three primary physical characteristics: the wings, the antennae, and the body’s waist.
Winged Carpenter Ant vs. Termite Swarmer
Wings: Carpenter ants have front wings that are notably larger than the hind wings, and the wings are only slightly longer than the body. Termite swarmers have two sets of wings that are nearly equal in size and significantly longer than the body.
Antennae: Carpenter ant antennae are bent (elbowed). Termite antennae are straight.
Waist: Carpenter ants possess a distinctly narrow, pinched waist, a trait shared by all ants. Termites have a broad waist, giving their body a uniform, non-segmented appearance.
This difference in size and shape also helps distinguish them from truly small house ants, such as Pharaoh ants, which are consistently smaller than minor carpenter ant workers.