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What are these BIG black ants in my house?

big black carpenter ant
carpenter ant

In early spring or late winter people often encounter these large black ants in homes. These big ants are different than the more common small, brown "nuisance ants" that plague kitchens. The big ants are called carpenter ants (Camponotus spp.) and unlike their smaller cousins, nest above ground in cavities. Nest building and cavity expansion by these large, powerful ants can cause damage if nests occur in our homes.

Most of the ants you find in homes are small, less than 1/4", and brown. There are several species of small brown ants that can nest in our home's walls or nearby soil and enter homes in search of food and water (see House Ants for identification and control). Nuisance ants are just that, a nuisance. They won't damage your home and pose no health threat of any kind. 

There's another ant, however, that occasionally is found in homes that is much bigger (1/4"-5/8"), darker in color, nests in the walls, floors and ceiling and can cause significant structural damage if not treated properly. People's first reaction often is "what are these BIG black ants in my home?" These are the carpenter ants and they can destroy the materials (structural wood, insulation, sheathing and so forth) that surround their nests. Thousands of dollars in home damage can be caused by a single carpenter ant nest as it grows.

Winged (left) and wingless (right) carpenter ants

Carpenter ants normally forage outside for food and water. Foraging ants will therefore move back and forth between their nest in a house and their hunting/foraging grounds outside. Carpenter ants are scavengers and predators taking whatever food they can find. The only time they normally enter the living space of homes is in late winter and early spring before their food sources develop outside. Therefore, if you find more than a few of these big black ants indoors, especially in spring, that's a pretty sure sign that you have a nest somewhere in the home. Don't be concerned about carpenter ants you find outdoors at any time of the year unless they are trailing into your home.

You may also find carpenter ants with wings (see photo above). These are the so called "reproductives" that start new colonies. Since this stage can easily shed their wings the ants you find indoors may have actually flown in through an open window or door. 

Once you confirm the workings of a carpenter ant nest in your home (see Inspecting Homes For Carpenter Ants) plan to treat the whole house (see links below). There is no need for "periodic maintenance treatments" advocated by some pest control companies, treat only when you know for sure that there's a problem.

Use the following articles to treat carpenter ant nests around your home. If you are handy you can probably do most of this work yourself, except perhaps repair of existing damage. If you are not so handy take a look at the article below about hiring pest control services.

Comments

queenzoonah said…
Is it usual to see carpenter ants around new construction? We're in our second year in this home, there were no signs last year, but now we've seen ants, in the front and back. Very wooded area out back, but not in front. Mulch is very low, and there is no soil near the siding. The slab is about 5" high all the way around.
It is not unusual to see carpenter ants around new or old construction, and it is not necessarily reason for concern. This is especially true near a wooded area. Carpenter ants can be very common so you expect to see them outdoors. If, however, they are "trailing" between the house and the yard this can indicate that there may be a damaging nest indoors and control may be necessary. See the carpenter ant links above for more information.
wchuck said…
I live in central Mississippi. I have never seen these big black ants before, and have lived in this house for 27 years. Mostly I have seen them outside, but I left the garage door open for most of the day and early evening, and found them on the walls in the garage. When I turned on the outside lights and went out, they were all over the sidewalks and driveway. Should I be concerned about this, and what is appropriate treatment for these ants when they're outside? Thanks!
My guess is you are seeing either a carpenter ant nest that is splitting (sometimes called budding) and moving, or the reproductive flight of a large nearby nest. This is not necessarily reason for concern as long as the nest is not located inside the structure.

Once this flight/migration has finished in a few days inspect around the house to see if ants are trailing to and from the house. If they are this means there's a nest in the house and needs to be treated. If not, the nest is likely located outside and does not not to be treated. See the Related Articles for more info.
Scott said…
We have started seeing carpenter ants at the same time we began installing porcelain floor tile in the basement. Are these related or not? We keep seeing the ants crawling across the tile as we are installing it, but can't determine their origin.
I doubt that the tile installation and the ants are directly related. If you regularly see carpenter ants indoors it probably means there's a nest somewhere in the walls, or possibly subfloor. Check outside for ants trailing to and from the house (see links above). If you need to treat see the links for perimeter sprays and carpenter baits that can be used.
Unknown said…
true and bu the way they only come in groups and they become very big and large. They only come into your house if there is a nest somewere inside your house
Mike said…
We live on the second floor of 3-storey wood frame apartment building. It is our first spring here. Also, we just finished having the laminate flooring throughout the whole apartment redone as well as a section of drywall replaced (damage from a burst water pipe). We had exposed concrete and interior walls for about 2 months. The work finished last week and since then we have found 6-7 big black ants around the baseboards where most of the work was being done. I imagine most pesticides are not meant to be used indoors. What can/should I do if I am worried about a colony forming? Thanks!
Mike,

Contact me at livingwithbugs@gmail.com and we can discuss this. The options are too involved to list here. Also, take a look at http://www.livingwithbugs.com/carpenter_ants.html for some background info.

Jack DeAngelis
Kirstin said…
A couple days ago, I found a few large black ants in my kitchen. Since the first few, I have vacuumed up 30 or more in my kitchen, and even have found a couple in the bathroom directly above my kitchen. I have been unable to find where they are coming from, but they just keep coming. I tried putting out my boric acid/strawberry jam bait that worked when I had a problem with small brown ants last year, but these ants are not remotely attracted to it. How can I determine if there is a carpenter ant nest in my house, and when do I determine if it is a large enough problem that requires a professional vs trying to treat it myself?
Jack said…
Kirstin,

This many ants probably means there's a nest in the walls or subfloor. You can control carpenter ants yourself but it can be a lot of work. Most people opt to hire a pest control company (there are suggestions on our site at http://www.livingwithbugs.com about hiring a PCO). Contact me at livingwithbugs@gmail.com if you want to discuss this.

Jack DeAngelis
mlada1033 said…
Our roof was reshingled this past week and around the 2nd day of noisy pounding etc. we noticed very large ants in the house (10-15) Is there a connection there? The roofer did not mention he saw any ants. We do have wood siding and alot of wood chips in our yard.
mlada1033,

I think this is more than a coincidence and probably means there's a carpenter ant nest in the roof. Take a look at the carpenter ant control options I've post at our 'Bugs site or contact me at livingwithbugs@gmail.com if you want to discuss this further.
Jennifer said…
I live in a small apartment on the top floor of a 3 floor building, and I have found maybe 10 large black ants wandering the walls of my kitchen and living room. Should I tell Management we might have a carpenter nest? Should I just put out traps and hope for the best? I haven't been home for the last couple of days, so I haven't seen any. But I'm not sure if I should tell Management, or if I'm just freaking out for nothing.
Jennifer,

If the ants are more than 3/8" they are very likely carpenter ants. Tell the management so they can have them treated. If you are concerned about pesticide exposure during treatment tell them this as well. If you live on the top floor the nest(s) is probably in the roof and the cause could be tree branches that have been allowed to touch the roof giving the ants an avenue on which to forage.

Contact me at livingwithbugs@gmail.com if you have questions.
Jackie said…
How many carpenter ants is okay to find in the house before you start looking for the nest? I have a room in the basement and have found myself surprised by a daily giant ant for a few days now.
Jackie,

This time of the year you can't really set a number. It is better to look outside for ants trailing between the house and yard where they forage for food. See the articles cited above for details about inspecting for carpenter ants. Contact me at livingwithbugs@gmail.com if you have questions.
ES said…
Its extremely hot here (over 100 degrees) and we have carpenter ant killers in the yard (the ones that go into the ground and are changed by the pesticide company). I've killed three ants in the house (we live on the bottom floor of a duplex condo), 2 by the door and 1 in the center of the house. I've never seen the ants come in the house before because of the outside treatment... I'm wondering if the heat has something to do with this? Could it be the heat destroying the pesticide faster? Or the bugs wanting to come in because of the heat and lack of flowers outside?
Sandra said…
I recently noticed several of these black ants in newborn baby's room by the door, and in the corners of the room. I have also found them in the corners of our room. After reading the article I realize it is these ants I am seeing but it is not early spring or late winter. We are in August. I am concerned because I do not want to think these ants may be crawling up into his crib or o him!
Brian said…
I just finished moving into my new apartment here in South Texas, last week I came across a big black ant, doesn't look like the one in the photo above (no enlarged thorax, everything fits size wise), but still half an inch! I couldn't kill it with a napkin, but it was no match for my boot.

Then tonight I see another one outside my pantry. I figure they're scouts since I've only seen one at a time. But would these still be carpenter ants if they appear as regular black ants but just significantly larger and are there any concerns: biters, stingers?

Thanks, Brian
Zema said…
I have tried to post this three times....so if it eventually shows up three times, excuse my ineptness with blogs!

I just had my house treated for carpenter ants. Part of the house is a two story structure. The tech said there was no need to treat the second story as the ants travel down at night to their nests. He did finally treat one wall as I have seen quite a few ants come from that wall. Why wouldn't you treat all four walls upstairs like they did downstairs? Is this customary or is this just a story to get out of treating the upstairs?

Thank you, Zema
Hope said…
I have not had any issue with any kind of ant until yeaterday. when I came hoem from work all was fine. About an hour later I went outside and was pelted with flying carpenter ants. There was wingless carpenter ants teeming all over the ground. It was as if the ground was moving. I couldn't believe it. did the wind blow them in? I had left the door open for a minute or two at one point as I stepped outside again. Since then I have been finding ants in the house - all over. I turn around and there is another. I think it is quieting down now. Should I still be concerned? Do you think they have moved in??
Unknown said…
I live in a wooden townhouse building which has 5 levels, including the patio roof top. My unit is on levels 3-5.

I have started to see the carpenter ants coming in (two yesterday on level 4 and one today on level 3). Are they coming in from the roof? The rooftop patio has a wooden floor (like a deck) on top of a metal sheet.

I had some trees in wooden barrels but they all died over the winter. I thought they dried out because of snow and wind. Could the carpenter ants be eating them to die?

I have an exterminator coming in. Please, help me where to look for htem. I am terrified of them. They are 2.5 cm! The exterminator (Orkin) said it would take up to a year to get rid of them, probably over 4 or more visits.
Unknown said…
Okay so we started seeing these big black ants with like a hard body in the kitchen. And now there are like 30 of them alongside the walls; all dead. Why is it that they keep dying besides where the wall meets carpet? And how do I get rid of them?
Unknown said…
I recently bought a travel trailer-pre-0wned. A few days after I got it home, I started seeing "big black ants" running around everywhere. My dad seems to think they were already in the travel trailer, what do you think? Thank you! carmen
Unknown said…
The former tenant of this duplex had my side with wood mulch that is rotted and yucky. Just had my son and his girlfriend completely uproot everything in the flower beds outside which is next to the house and now am starting to see them inside in the kitchen under the window. So, I shut the window but know that won't keep them out. Since they are inside, could there be a nest in the wall or should I just assume the wood chips are attracting and after I get that all cleaned out and rocked they will go away?
Unknown said…
I found a large black ant that fits the Carpenter Ant description crawling up my front porch. Of course I killed it and haven't seen another yet (1day). However, my neighbor also found one in her yard. Would these be scavengers? We live in a sub division that is surrounded by dairies and farming. Should we be concerned if we only see one or two?
Unknown said…
It is June 20th and I live in the Greater Cincinnati area. I have small black ants, and big black ants in my home. Could my big ones be carpenter ants, even though it isn't really spring anymore? I have not seen any with with wings; just large black ants.
Laurie said…
Help! I have large black ants in kitchen and we found them on pastry that was wrapped in foil, I heard something scurrying around and opened it to about twenty of these big black ants. Its August and is it comman for carpentar ants to eat your sweets. Also, my son and husband was out digging up wood post that had all these big ants on the post, could they possibly brought some and if so can they grown into a large nest that quick? We do live in a cedar house surrounded by woods and cornfields. When we sprayed these ugly ants they went up to our wood ceiling and I am guessing they may be in there, or they came in that way. It was just shocking to see that many large black ants eating my sweets. Any advice you can give would be greatly appreciated
Thanks, Laurie Decker
Abhay Nadkarni said…
We moved into this single family 2 floor+finished basement house in Nov last year and the home inspector prior to the house sale had noticed couple of carpenter ants in the garage.

The previous owner did a treatment through a company Terminite and i do have a 1-year warranty.

A month or so ago, i did start noticing 1-2 ants a day and couple of days back when i came home in the evening, i must have flushed out 20-30 ants, the next day almost a 100 and yesterday about 30 odd.

All of these ants appear from nowhere in my kitchen and family room.
I did notice 1 odd ant total so far in the basement and maybe a couple on the 2nd floor so far.
I did notice a dead queen ant in one of the 2nd floor bedrooms.

I have arranged for a treatment again from the same company.

Could you advise what i need to tell them or insist upon? Does the whole house need to be treated?
Unknown said…
So.. We had a new garage installed today and now we see inch long if not bigger (like OMG that;s a huge ant big) all around the house, crawling on the outside walls, seen a couple inside the house and seen them right a long the pavement connecting to our house.Do we likely have a problem with carpenter ants? I know we already have a regular ant problem, but these are new and hadn't showed up until after the how deal with a new garage door being put installed.
Anonymous said…
HELP, we just spotted a number of big black ants that started coming from under our baseboards in our dining room. I have killed over 40 now in the last few days and I am really worried. How do we get rid of ants if they are in our home and how costly will the treatment be?
Linda said…
Are the big blank ants that are on Peony Bushes the same as carpenter ants
Unknown said…
Can these bugs hurt you? Like bite or anything? I've seen several in my home and one just crawled on my bed where my 2 small children are sleeping.
worry wart said…
We came home and found a big black ant crawling across our carpet does that me there are many if we found one
Unknown said…
Hello! we've lived in our condo for 8 years.. we're on the 5th floor and our condo is made of stone.. a few days or maybe a week ago i have seen only 2 or maybe 3 of these winged carpenter ants with some normal size ants but lately they began to increase in number even the normal sized ones.. they can only be seen in our masters bedrooms comfort room and nowhere else (im referring to winged carpenter ants not the normal-sized).. based on your post, they only appear during spring/winter and some wood-y places.. but we're from the Philippines, we only have two seasons (wet&dry) and as I've said earlier our condo is made from pure stone.. its why I'm really curious if wether we should be alarmed by it or not.. any opinion on the matter? its the first time that this kind of thing happened here.
Unknown said…
Today I just found the largest ant I've ever seen in my kitchen sink. At first I thought the way it was laying that it was an odd looking spider and thought it to be dead.. I tried to wash it down the drain and the thing started running! Larger than a fly, but does not quite resemble the carpenter ants pictured. The body consisted of 3 larger round circles. I scooped this thing up and took it outside where it was seen by the rest of the household and killed. Should I be worried that we have more of these things in the house? And could the possibly be a carpenter ant?
rouge0325 said…
HELP!!!!! The ants go marching in my house, oh no, oh no! My problem is unlike anything I've read so far. This started around the beginning of spring. We have a small Maltese who uses pee pee pads. One day my husband and I came home and from a distance, there was what looked like a 6-8" diameter black spot on her pad. We went to look at it and the spot started moving in all directions! It was hundreds of HUGE ants gathered on the spot where our dog urinated. We were both stomping like mad! We just couldn't kill them all they scattered so fast. We have had a few of the small sugar ants in the past but never this giant beast. My husband got some spray and went outside and sprayed all around house, obvious hills and holes. It cut down on the number but we still had some. Tonight, same story. Only, TWICE AS MANY on pee pad! I have a medical background, so my hypothesis is they may be attracted to any excess glucose excreted in urine if dog may have diabetes or Cushing's disease. However, are Carpenter ants usually attracted to sweets? Are these definitely Carpenter ants? I have even been bitten twice by them. We are stumped! We would greatly appreciate any advice, direction, education, recommendation you can parlay through your expertise! Major concern, too, we have two grandchildren age 3 and 4 months in which we do not want exposure to any harmful chemicals.
Thank you!
Contact me through this page http://www.livingwithbugs.com/ec.html and we can discuss control options.
Andrea said…
Can they come in with the firewood?
Unknown said…
I just moved into my house May 1st. We did a lot of construction all of April so the doors were all wide open. Since living here I have seen 6-8 large black Amy's in my house. But they are in 3 different rooms. Should I worry the colony is inside or outside?
Unknown said…
Hi my name is Elizabeth I see these ants in my home I just seen my first one yesterday of the year we had a big problem last year with them and told my mom to contact someone about it and she said that they weren't carpenter ants but it looks like the one in the picture they have thos claws in there face and try to get food in our kitchen can someone respond back to me are they carpenter ants? My house is over 100 years old I just want to know and my mom says there not thank you
I found one of these tonight but I wouldn't consider this time of year to be early spring as we are so close to June. Could it be an isolated incident? Or is this a sign of more?
Unknown said…
Hi I found one of the giant suckers in my kitchen a coupe of weeks ago, I tracked it until it disappeared under the lip of the kitchen counter, the thing was about 3 inches long and an inch thick, made me jump and I was perplexed on how it disappeared I can detect absolutely no holes there, Just tonight I found another one climbing down the wall of my bedroom, this time I killed it. What are the chances of a nest based on this?
Unknown said…
Yes! The same thing happened to me- I live in Southern Texas near the border. One day we got back home late and they were flooding on our driveway and by our front door! We had to spray the yard with a pesticide to get rid of them fast as possible since I have two small children. Their safety was my number one concern. We sprayed the entire yard twice (and nearby tree as that was where they were nesting). I have only seen one black one so far and it has been about two or three months. Find the nest ASAP.
Amy C. said…
Is this page still active? I have seen several of these big ants in my family room over the past few days, many of them dead or dying guessing from a perimeter spray that was used when we first moved into out house in Sept. However, I am very concerned as to where this nest might be...I typically find them near a sliding door with a wood frame but there is no visible damage to wood. I re-sprayed inside yesterday. Why are they coming inside during the fall/early winter? Is therr anuthing else I can do to kill them all? This grosses me out.
Unknown said…
I have seen carpenter ants in the house since we had our first tour of our home. I thought at the time it wasn't a big deal since no one seemed to be living here. Big mistake!
We have been here for 10 years now and cannot get rid of them. Once we cut down some trees in the back yard and were absolutely infested for a year. Once we cut out a wall to install a window and the whole interior of the wall seemed to be a mummified nest.
They seem to appear in February. Last year we moved out of the kitchen for a month and kept most of our food in the living room. I sprayed raid in there every day. Then we ripped our entire kitchen out and replaced everything except for the window and we were out of the kitchen for another month. I thought this would surely get rid of them until last week.
I opened the door to the garage which is off the kitchen and the threshold was covered in ants 50-100. I tried stomping them but they scattered fast. Since then I have found over 100 in the kitchen. (Typically 10-20 per day.) what am I going to do? What is wrong with my house?
Unknown said…
We have seen two or three carpenter ants in our home recently...two on main floor but one upstairs in a bedroom. We have two bradford pear trees nudging up against our home - could this be the way they are getting in? My main question is: if you have only seen two or three of these (and each of them alone at the time we see them), how do you locate the trail/nest and how do you then treat the prevention of more of them entering the home?
Unknown said…
Safety was a concern yet you sprayed chemicals all over the yard. Duh.
Unknown said…
Actually those big ants are carpenter ant queens and male elites but no workers
John Grehhem said…
Hello!
JJ said…
I have recently killed 6 carpenter ants in my kitchen in the floor. I have been in this house for 36 years and never had ants before. When do I need to act?
Milanko said…
I just found a big black ant and crushed it. It was so bug its guts splatterd my shirt. There was only one big one and dozens of tiny ants in my sink with it. Was this a carpenter ant?

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