Fire ants and carpenter ants are two common ant species found in many parts of the United States. At a glance, they may appear similar, but there are some key differences between them. Understanding how to identify each species and their unique behaviors and threats can help homeowners know how to control them.
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Quick Facts
Here are some quick facts about fire ants and carpenter ants:
- Fire ants are reddish-brown in color and have a painful sting. Carpenter ants are black and do not sting.
- Fire ants build mounds outdoors. Carpenter ants nest indoors or outdoors in wood.
- Fire ants feed on insects, plants, and sugary substances. Carpenter ants feed on wood and sugary substances.
- Fire ants are aggressive and will defend their nest if disturbed. Carpenter ants are not aggressive.
- Fire ants can bite and sting multiple times. Carpenter ants have mandibles for chewing but cannot bite or sting.
Appearance and Identification
One of the easiest ways to distinguish between fire ants and carpenter ants is by their appearance:
Fire Ants
- Size: Worker fire ants are 1/8 to 1/4 inches long. Queens can be up to 1/2 inch long.
- Color: Reddish or brownish-black
- Body: Oval-shaped with a pedicel (narrow “waist”) between thorax and abdomen
- Legs: Long legs with bent knees
- Other: No uniform hairs on body
Carpenter Ants
- Size: Worker carpenter ants range from 1/4 to 1/2 inches long. Queens can be up to 3/4 inch long.
- Color: Black
- Body: Segmented, narrow waist between thorax and abdomen
- Legs: Long legs but more angular than fire ants
- Other: Even coat of fine hairs covers the body
When inspecting an ant, take note of their color, body shape, length of legs and antennae, and presence of hairs on the body. These clues will help identify whether you are dealing with a fire ant or carpenter ant.
Nests and Habitats
Fire ants and carpenter ants build their nests in different areas:
Fire Ant Nests
- Outdoors in soil
- Constructed as above-ground mounds up to 18 inches tall
- Dome-shaped with visible entrance holes
- Can have multiple mounds connected by foraging tunnels
- Prefer open, sunny areas like lawns, parks, and roadsides
Carpenter Ant Nests
- Indoors or outdoors in wood
- Hollowed out galleries in logs, stumps, trees, or wooden structures
- No external mound visible
- Nest inside existing cavities and cracks in wood
- Can nest in moist, decaying, or hollow wood
When trying to locate an ant nest, look for the telltale signs of each species. Fire ant mounds are obvious structures in yards and open areas. Carpenter ants create no visible nest, but chewed wood, sawdust piles, and hollow sounding wood may indicate their presence.
Diet and Foraging Behavior
Fire ants and carpenter ants do not eat exactly the same foods:
Fire Ant Diet
- Insects and insect larvae
- Earthworms
- Spiders
- Plant sap
- Nectar
- Honeydew from aphids
- Seeds
- Human foods like meats, oils, and sugar
Fire ants are omnivorous and opportunistic feeders. They forage up to 100 feet away from the nest on well-worn trails. They are aggressive defenders of food resources.
Carpenter Ant Diet
- Wood and wooden structures
- Dead insects
- Sweet things like nectar, honeydew, and sugar water
- Fruits and plant sap
- Kitchen foods and human food scraps
Carpenter ants eat wood and excavate it to form their nests. They prefer moist, decaying wood. They also feed on sweets and forage up to 100 feet from the nest.
The main difference is that fire ants actively hunt insects while carpenter ants only scavenge dead insects. Fire ants also do not eat wood.
Behavior and Aggression
Fire ants and carpenter ants behave very differently:
Fire Ant Behavior
- Very aggressive – will quickly attack if nest is disturbed
- Inflict painful stings that form blisters
- Swarm threat – multiple ants can sting repeatedly
- Deliver venom through sting that contains alkaloid poison
- Sting leaves a small, red welt that blisters
- Bite with their mandibles and then sting simultaneously
Carpenter Ant Behavior
- Not aggressive – try to flee rather than fight
- Do not sting or bite
- May spray formic acid for defense, which can irritate skin
- Mandibles can pinch but cannot break skin
Fire ants will boldly defend their nest if disturbed and aggressively attack intruders. Carpenter ants are not aggressive and their first instinct is to flee danger.
Threats to Humans and Pets
Fire ants and carpenter ants pose different threats:
Fire Ant Threats
- Painful stings can cause blisters, pustules, and scarring
- Swarming attacks if nest is disturbed
- Sting venom contains alkaloid poison that can cause allergic reaction in sensitive individuals
- Stings around eyes or throat can be medical emergencies
- Can bite pets but usually do not attack unprovoked
Carpenter Ant Threats
- Do not sting or bite
- Can transmit diseases by contaminating food in homes
- Cause structural damage if nest goes unnoticed in walls or wood
- No direct danger to pets
Fire ants can inflict painful stings with their venom. Carpenter ants cause no direct harm but can spread bacteria and damage structures with nest excavation.
Controlling and Preventing Infestations
Different control methods are required for fire ants versus carpenter ants:
Fire Ant Control
- Locate and drench mounds with boiling water or insecticide
- Apply broadcast insecticide over entire yard
- Use ant baits near mounds
- Dust insecticide around home foundation and entry points
- Eliminate standing water
- Keep yard free of debris piles
Carpenter Ant Control
- Inject insecticide directly into nest galleries
- Apply insecticide spray or dust to ant trails and entry points
- Use baits near trails and suspected nest sites
- Find and remove moisture sources
- Replace damaged wood
- Keep food sealed and clean up spills
For fire ants, treatment should focus on the yard and mounds. For carpenter ants, finding and directly treating nests is key. Reducing moisture and food sources helps deter both species.
Key Differences Summary
Here is a summary of the main differences between fire ants and carpenter ants:
| Feature | Fire Ants | Carpenter Ants |
|---|---|---|
| Appearance | Reddish-brown; oval body | Black; narrow, segmented body |
| Nest Location | Outdoors in mounds | Indoors or outdoors in wood |
| Diet | Omnivorous; eat insects, plants, sweets | Primarily wood and sweets |
| Behavior | Very aggressive | Not aggressive |
| Sting/Bite | Painful sting and bite | No sting or bite |
| Threat to Humans | Painful stings | No direct threat |
Conclusion
In summary, while fire ants and carpenter ants are both common ant pests, they have significant differences when it comes to appearance, nesting, diet, aggression, and threats posed. Understanding how to identify each species is important for proper control and prevention. Fire ants are best managed by treating outdoor nests and reducing habitat favorability. Carpenter ants require locating indoor nests in wood for targeted treatment. Being able to differentiate between these two ants will help homeowners know if they need to take action for their comfort, health, and home protection.