It's a fascinating micro-society of a socialistic Monarchy.

Winged male and female carpenter ants (aka. swarmers) emerge from mature colonies usually from March to July. After mating, the males die and each newly fertilized female establishes a new colony in a small cavity in wood, under bark, etc. The first brood of larvae is fed entirely by the queen. She does not eat, but metabolizes stored fat reserves and wing muscles for nourishment. The few workers emerging from the first brood assume duties of the colony, such as collecting food (the carpenter ant diet consists of a wide range of plant and animal materials), excavating galleries to enlarge the nest, and tending the eggs, larvae, and gallery walls so as to warn other colony members.

Carpenter ants are most active at night. Large numbers of foragers emerge very soon after sunset to search for food. Foraging ants bring food back to the nest to feed the larvae; they may carry food items in their mandibles or they may consume the food and store it in their crop. Carpenter ants are omnivorous, and they feed upon a great variety of both plant and animal materials, including insects (living or dead), plant juices, fresh fruits, honey, jelly, sugar, syrup, meats, grease, fat, etc. Carbohydrates are the primary energy source for workers. One of their most common, readily available, and preferred foods is honeydew, which is a sugary substance excreted by aphids and scale insects feeding on the plants. (Landscape plants infested with these plant-sucking insects are a good place to inspect for carpenter ants.)

"To keep a constant replenishing supply of honeydew, ants will kidnap a herd of aphids and hold them captive near the nest. These aphids will then attack your plants. It's been said time after time and one more time; if you can control the aphids you can control the ants." Ant Control

Carpenter ants travel along well-established trails between nest sites and feeding sites. Workers may forage for food as far as 100 feet from their nest. Outdoors, look for ants traveling from a tree cavity or stump to the structure. Foraging ants may travel over tree branches or vines touching the roof, electrical and telephone wires, fences next to the house, piles of firewood, logs, railroad ties, etc. They may be seen walking on plants, tree trunks, and rotten wood stumps. Their trails often extend through the lawn.
The carpenter ants' food preference appears to change on a seasonal basis, which is related to the typical brood production cycle. The larvae require protein-based foods (the quantity and quality of nitrogen in the protein are key factors that affect ant growth and development). A field study in Virginia showed that C. pennsylvanicus protein collection peaked in June and again in September, months when older larvae were present in the nest.

from The Ohio State University Extension Office