Camponotus pennsylvanicus

School of Ants collection
Literature record

Camponotus pennsylvanicus

From Dr. Eleanor's Book of Common Ants

A.K.A.: Black carpenter ant

Size: 0.25-0.5 in

Where it lives: Black carpenter ants prefer to nest in living, standing trees, but will also nest in logs and wood in human structures.

What it eats: Omnivores, black carpenter ants eat protein foods, including other insects, as well as sugary foods.

What’s the big deal?

The black carpenter ant, Camponotus pennsylvanicus, is one of the United States’ largest and friendliest ants. Because of their size and pleasant disposition, they make excellent ambassadors between the ant and human world.

When I was little, I took my breakfast crumbs out to the front yard to feed the black carpenter ants living in the willow oak trees. I built little piles of bacon and toast for them on top of oak leaves and waited for them to lumber out from holes hidden in the bark at the base of the trees.

You can identify black carpenter ants by looking at their size (BIG) and the light dusting of golden hairs on their head and thorax and settle on their abdomens. Unlike some ant species, black carpenter ant workers vary in size and shape within the colony (Fowler 1986). Between 1/4 and a little over 1/2 inch long, a small black carpenter ant can comfortably straddle a plain M&M, and a large one can just about straddle a dime. Colonies have between about 350 to almost 2,000 workers, which, depending on worker size, works out to be almost 200 dollars’ worth of dimes banging around inside those trees or, more deliciously, up to 40 bags of M&Ms (Tripp et al. 2000).

Breakfast for Ants

I loved those ants. I was fascinated by the way they walked around like miniature black horses, exploring their way with their elbowed antennae, stopping every now and then to gently tap their sisters and give each other waxy kisses. If I pressed my ear against the tree near their entrance way, I could hear them crackling about their business inside. If I sat still, they would come up to my hands and gingerly pick crumbs off my fingers. If I picked one up, she would explore my arm and shirt. If I squeezed her, she would give me a pinch with her tiny jaws. It never hurt.

They’re called carpenter ants because they are particularly good at woodworking. They like to nest in living, standing trees using their sturdy mandibles to excavate tunnels and rooms in the wood (Klotz et al. 1998). Many people see black carpenter ants living in their trees and think the ants are killing the trees. However, black carpenter ants actually have a history of helping trees. They have an appetite for tree pests like red oak borers, and they spend a lot of their time foraging around their home, plucking pests off the bark (Verble and Stephen 2009, Muilenburg et al. 2008). The trees housing my carpenter ants 25 years ago are still standing today.

Because of these woodworking skills, some people think carpenter ants are pests. While black carpenter ants can make their tunnels in the wood of people’s homes, they often point homeowners to bigger problems: damp and rotting wood from a leak or drip or other pests living in that wood. When wood becomes soaked through, carpenter ants can easily use their jaws to snap away and build their tunnels. If homeowners keep their wood dry, carpenter ants will usually stick to the trees. That is, unless the homeowners have pests like termites or wood beetles snacking away inside their walls.

Sometimes black carpenter ants will happen upon such a treasure trove of food and set up camp right next to their grocery store. Can you blame them? Haven’t you ever dreamed of living next to your favorite doughnut shop or fried chicken restaurant? Instead of attacking carpenter ants for living in the walls, use them as helpful guides to identify the real problem. These little canaries in the coal mine could have a lot to tell you!

I used to think my carpenter ants might like some of my bologna sandwiches from lunch, but I couldn’t get as many takers at lunchtime as I got early in the morning. That’s because carpenter ants are mostly night owls (Nuss et al. 2005), foraging from dusk until dawn. Black carpenter ants have pretty good vision for ants, using that vision to help them take shortcuts from their house to food in the early morning and when the moon is out.

Ant Speak: Decoded

When they aren’t following their sisters’ chemical trails, they remember landmarks like pebbles and sticks to help them find their way home. These landmarks save time for black carpenter ants, who can forage up to 100 yards from their nest. That’s the human equivalent of walking over 11 miles for food. On new moon nights when it is totally dark, black carpenter ants take no shortcuts and feel their way through the night, keeping their bodies close to structures (Klotz and Reid 1993).

When carpenter ants find food, they run back to the nest, laying a chemical trail behind them. Once inside the nest, they do an “I-found-something-awesome” dance to get their sisters awake and excited enough to follow them. The hungrier the ants, the more vigorous the dance (Traniello 1977). The excited sisters then rush out of the nest in search of the chemical trail that leads them to the food. Carpenter ants, like many other ant species, have little built in knapsacks called crops inside their bodies. They stuff these crops with food to take back home (Cannon and Fell 2002). When they meet their sisters on the trail, they stop and have a little conversation that goes something like this:

Ant heading out to food: “Hey, what’s up?”

Ant returning from food: “Are we from the same nest?” (They do this by tapping each other on the head with their antennae to see if they smell alike.)

Headed out ant: “Yeah, but I’m not sure what I’m even doing here. I’m just following this trail.” (She moves her tapping antennae closer to her sister’s mouth.)

Returning ant: “Oh, wow! I should have told you earlier. Some kid spilled his Dr. Pepper down the street and it is DELICIOUS. Everybody’s over there now drinking it up. Want to try?”

Headed out ant: “That sounds awesome. Of course.”

Returning ant spits a little droplet from her crop into headed out ant’s mouth. Headed out ant drinks it and agrees it is awesome. Awesome enough, in fact, to continue running down the trail.

When I was a child, I saw black carpenter ants having these sorts of conversations all the time and thought they were kissing. When I grew up, I learned that I already knew much about black carpenter ants from watching them as a child. Their colony size, where they nest, and how they eat are all scientifically dissected and explored as thoroughly as the ants themselves explore the dark tunnels of their homes. Scientific papers explain how they talk to each other, when they’re awake, and why they don’t want bologna on hot summer afternoons. Every delicate golden hair on the black carpenter ant’s rump has been counted and catalogued. These discoveries took many decades to document. All of them can be made any morning by each one of us, holding our breakfast crumbs, waiting patiently in our front yards.

Find out more about this species at Antweb and see more photos at Alex Wild's photography site.