Results matching “pavement”

Brown ants moving in mass along sidewalks

Hello, I am in Toronto and have located a colony of small reddish/brown ants living under the 6x6 wooden ties surrounding my lawn. My question is: are these ants beneficial to the eco-system and should therefore be simply left alone? I have a wooden porch: should I be concerned about 'an invasion'?
Secondly, I have occasionally seen the same type of ants moving in mass across sidewalks - thousands of them - so many that it looks like a brown stain on the sidewalk. Can you tell me what causes this phenomenon?
Thanks for your help,


Dear Mary,

Thanks for writing to the AntBlog! It was a pleasure to answer to your interesting questions.

Ants play a huge role in an ecosystem: they are diverse (we estimate 30,000 ant species living on Earth), and are in great numbers everywhere (all the ants weigh almost the same as the 7 billion human beings). Along their evolution, ants established ecological relationships with a large array of plants and animals. They are prey, predators, symbionts, parasites (there are even slave maker ant species!), seed dispersers, pollinators, and so on. Ants move more soil than earthworms. They impact and are impacted by almost everything surrounding them. More, they have a short lifespan, and that means their nest population is constantly being replace by new generations of ants. So, if something happens with an environment you will notice the effects faster and with more details if you look at the ants, and it will be much more effective than looking at birds or mammals, for example.

Just for curiosity, ants are important for other aspects of human societies. Their behavior is used as model to create smarter traffic lights, or to develop software that will evaluate the response of our bodies to the effect of new drugs (see here, here, and here). Anti-inflammatories, antibiotics, and even drugs to fight against cancer were/are being developed with substances ants secrete (here, here, here, here, and here). Finally, have you ever thought of including ants in your menu? Many human cultures around the world did! See here.

Salad of Oecophylla smaragdina queen brood mixed with some worker ants, mint leaves, spring onion, chili, and fish sauce. Popular in Thailand and Laos. Image by Joost Van Itterbeeck/

Based on the behavior you described, I believe you found pavement ants (genus Tetramorium). Unlike carpenter ants (genus Camponotus), pavement ants don't cause any structural damage to your house (and just to take Camponotus out of the fire, those ants nest in decayed wood; so, if the wood in your house is in a good shape, carpenter ants will not be a problem).

Pavement ants get their name because they nest usually underneath or at the edge of sidewalks, and other hard surfaces. They are an introduced species from Europe; and in your garden they will: harvest seeds -- some of which will eventually grow around their nests; tend insects on plants, collecting sugary dropping they produce (A.K.A honeydew), and protecting them from predators; and predate other insects.

The pavement ant workers are dark reddish-black, about 2.5-4 mm long; the petiole, which connects the mesosoma (i.e., the modified thorax of ants) and gaster (modified abdomen), has two segments. The posterior part of the mesosoma has two spines that project upward, and they have a stinger in the last abdominal segment.

Lateral view of Tetramorium caespitum. Image by Will Ericson/

When two pavement ant colonies overlap, worker ants leave the nest to establish their territory boundaries before ants from the other nest push them out of there. Then, ants coming from each nest collide in a massive battle. The combats are sometimes ritualized: they will just size each other strength, and produce very few casualties. In another occasions, they will ripe one another apart, and thousands of corpses will be left on the sidewalk afterwards.

Sidewalk ant war. Image by the fabulous Alex Wild (


Flavia Esteves and the AntAsk Team

Dear Ant Experts,

You really can find anything online! I'm so glad I found your website. Please help me as I can't identify these flying ants.

In prior years I've noticed these flying ant like bugs outside my home. A few days ago I noticed two in my kitchen. Then the next morning about a half dozen. Same the next day. This morning there weren't that many.

I've been looking for information to identify them when I found your site. They don't exactly match the pictures of either ants or termites I've seen online. They look more like flying ants but with very small heads. The time of year and other behavior doesn't seem to match up with things I've read online.

They move around clumsily as if they're not used to having wings. I found some dead that appeared to have fallen on their backs and couldn't get up. I am located in the north east NJ.

Please help me figure out what I have, where they might be coming from and what best to do about preventing their entry in my home. Spending hours looking at pictures of bugs online is starting to creep me out :)

I've included some pictures. Wish I could have taken better but hoping that along with the description is enough.

Thank you,

This morning I saw dozens of these flying ants in my kitchen and I desperately need something to do about them. I'm worried I may have to call an exterminator. Two things concern me. 1) I may not have termites and they tell me I do and charge me extra which I can't really afford. 2) I may have termites and I won't treat effectively for them.


Dear Tom,

Thank you for contacting AntBlog!  I am sure you can image that around this time of year we receive many emails regarding ants in peoples homes. 

The ants you found are the common pavement ant, Tetramorium cf. caespitum.  These are the ants you can often see waging battles between the cracks in the sidewalk.  Winged forms you are finding are sexuals (the males and females) that are produced about once a year to found new colonies (you can read more about how to identify the sexual forms here).  The release of these sexuals usually coincides with the first really hard rains of the season or other environmental cues. 

You can read more about pavement ants in these four previous AntBlog posts:


If you are not seeing any of the wingless workers (typical ants) walking around your home, you likely just have your house in the way of their flight path.  These ants are not very commonly found in homes and do not cause structural damage like termites or carpenter ants.  But, if you start to see large numbers of the workers in your home to you can try some of the tips on these two posts:


Best regards,
Corrie Moreau & the AntAsk Team

Territorial battles

Hello from Brookfield, Wisconsin.

It's great to see this service online--yet another wonder of the Web.

My question involves small (not much over a millimeter long), red ants that nest around our home and seem particularly to like areas near our front walk.

More than once I have noticed these guys flowing onto the concrete and forming a large gathering in the open air--see attached photos.

Why do they do this?


Small Red Ants 1.jpg

Small Red Ants 2.jpg

Hi Ted,

These are a species of pavement ant, Tetramorium caespitum. They are common in urban areas, hence their common name. The event pictured is a large territorial battle between colonies. Territoriality is common in ants as a whole, varying by species and colony age. Ants typically protect their territories for access to food or nesting space.

The closely related Japanese pavement ant, Tetramorium tsushimae, is similarly territorial to the pavement ants that you see in Wisconsin. In this species, colonies with larger territories containing larger numbers of seeds and other food resources are able to raise larger numbers of reproductive individuals. However, food is not the only factor determining colony success. The ideal temperatures for raising queens and males are between 27.5 and 30 degrees Celcius (81.5 to 86 degrees Fahrenheit) and colonies also engage in territorial battles to gain access to nesting sites with these temperatures. Therefore, the pavement ants on the sidewalks outside your house are probably fighting for access to both food and optimal nesting sites.

While fights among pavement ants often lead to the deaths of large numbers of workers, this is not a requirement for ants to maintain territories. A species of honeypot ant, Myrmecocystus mimicus, is also highly territorial, but, rather than risk the lives of workers, engages in ritual displays. Hundreds of ants from each competing colony confront each other and stand as tall as they are able while inflating their gasters to appear larger. Eventually, a winner is decided based exclusively on the differences in workers between colonies and territory is ceded to the apparently stronger colony. If colonies are drastically different in size then the smaller colony will be destroyed but otherwise, no physical interactions occur. You should take a look at the papers listed at the end of the post if you want to know more details.

Thanks for your question,
Ben Rubin, James Trager, & the AntAsk Team

Holldobler B. (1981) Foraging and spatiotemporal territories in the honey ant Myrmecocystus mimicus Wheeler (Hymenopera: Formicidae). Behavioral Ecology and Sociobiology 9: 301-314.

Sanada-Morimura S, Satoh T, Obara Y. (2006) Territorial behavior and temperature preference for nesting sites in a pavement ant Tetramorium tsushimae. Insectes Sociaux 53: 141-148.

Winged ants sendoff

We've observed swarms of pavement ants all over the neighborhood and found out via the internet that this is to send off the winged queens and males to start new colonies. Assuming this is correct, I still have a couple of questions. First, why do so many worker ants need to swarm? Does this serve a useful purpose, like distraction or something? They just seem to be going in all directions (and occasionally moving pine needles and things). Second, as I was crouching over one swarm the ants dragging the winged ants seemed to switch directions and pull the winged ants back into the nest. Would there be a reason for them to do this, like because of my presence, or some other prompt, or was it just a coincidence?

Hello Anne -- Thanks for writing the antblog with this question, which I think will be of broad interest to ant observers. It is true, as you say, that ants send off winged individuals to start new colonies. These mate away from the parent nest, often in a mid-air swarm composed of winged ants from many different home nests, thus ensuring outbreeding. After mating, males soon die, but the females go to a suitable nesting site, break off their wings, build a small nest, and attempt to raise a batch of workers and thus become a colony queen. Most foundress queens fail, due to predation, desiccation, fungal infection, etc., which is why ants send out so many winged females during the life of the colony.
Ant colonies invest a lot of food and energy into brood rearing generally, especially into rearing the large reproductive forms. So they protect this investment the best they can for as long as they can, up until the last moment, when the winged ants fly off. A swarm of worker ants can intimidate potential predators from approaching the winged ants, and when they workers detect a giant form or shadow (such as yours), they try to protect their winged brothers and sisters by dragging them back into the nest. They also do this when changes in weather (sometimes even a mere gust of wind or small cloud blowing over) indicate possibly unsuitable conditions for a successful mating flight may arise. The more healthy winged ants they can keep alive for the eventual mating flight, the more likely it is a particular colony's genes will make it into future generations of their species.

James C. Trager of the Ask Ant Team

Transfer colony to new farm (Justin)

How difficult, if possible, is it to transfer an ant colony from a small easy maintenance starter farm to a much larger farm. Also how big would my farm have to be to have a full colony of pavement without 'controlling' population size? I can build one as big as I need. And what are the chances that my pavement ant colony will have more than one queen producing, I read that they will sometimes have more than one producing queen per colony. I think it would be very interesting to watch a multi queen colony.

Thank you so much,

Dear Justin,

It should not be too difficult to transfer your colony to a new farm, though you will probably lost some individuals in the process. Take a look at our previous post here.

I doubt that there will be any need to "control" the population size. The colony will grow until it is mature or runs out of resources so keep it well fed and it should be fine. Pavement ant colonies can grow to tens of thousands of workers so if you want your colony to reach its maximum possible size, you should probably make the farm rather large. Be sure to take a look at this previous post for tips on building a habitat.

Steiner et al. (2003) found multiple queens in five of 35 pavement ant colonies collected, so it is certainly possible that your colony contains multiple queens. Although you may need to do some more whole colony collecting if you are determined to find this type of colony.

Good luck with the farm!
Ben Rubin & the AntAsk Team

Steiner FM, Schlick-Steiner BC, Buschinger A. 2003. First record of unicolonial polygyny in Tetramorium cf. caespitum (Hymenoptera, Formicidae). Insectes Sociaux 50: 98-99.

Ants on Hot Pavement (Anna, Unknown)


How come when it gets really hot ants are still able to run around on bitumen and pavers without burning their feet?

Anna W

Dear Anna,

Although the thermotolerance of ant tarsi (feet) on hot bitumen or pavement has not been directly studied, there are a few biomechanic studies out there that can help us make some educated guesses.

Part of the reason ants may be able to run quickly over hot pavement is that their tarsi are composed of sclerotized chitin, which is a really tough polymer of many connected glucose molecules. The toughness of this biomaterial is often compared to the keratinized tissue seen in vertebrate hooves--such as horse hooves--many of which are also able to walk on hot bitumen and pavement. This is very different than human feet, which have many nerves and soft, burnable tissue on the bottom of our feet. Yet, even humans can walk on hot pavement if repeated friction and pressure forces the formation of calluses that insulate the sensitive tissue in your foot from the pavement.

While this explanation helps us understand how ants don't burn their tarsi (feet), it does not get around the larger of issue of how the ants on hot pavement deal with the increased body temperature (ants are small!). Well, as it turns out, there are some extremely interesting studies on ants that have adapted to hot, dry environments. One ant in particular--the Sahara Desert ant (Cataglyphis bicolor)--has adapted such a high thermotolerance that its proteins can operate at higher temperatures (4-5 degrees Celsius) and it can forage normally at body temperatures above 50C or 122F. Considering this ant makes a living by running on the hot sand to find and consume insects that have died of heat exhaustion, it makes sense that it can withstand this heat. While you wouldn't commonly find Cataglyphis running on pavement, there has been recent research showing that ants found in urban and suburban areas are more likely to come from hotter, drier habitats because of the prevalence of open areas in the urban and suburban landscape. Thus, it is logical that the ants you see running around on pavement might have also have some thermotolerance themselves!

Thanks for your question,

Max Winston & the AskAnt Team

I'm thinking about doing a science fair project on ants. I was hoping to create a habitat for two colonies of ants and then connecting them by removing a plastic divider. Wanted to observe what the colonies would do and how it would change their behaviors finding food, etc. Also, I read that certain ants can float by linking together on top of water. Is this true? Will ants from two colonies link to survive?


Hi Marion,

We have several posts on ant farms here, and particularly this post might be of interest to you.

Almost all ant species will viciously defend their colony against ants from a different colony. This being said, once you remove the plastic divider, the two colonies would fight each other. If the two colonies are from the same species, workers usually fight one-on-one in often lethal fights and the larger colony would win. Check out this post by Alex Wild on territorial fights of pavement ants. If the ants you bring together are from different species, it is hard to predict which one would survive.


Two pavement ant colonies fighting (Tetramorium). Photo by Alexander Wild (

To answer your second question, fire ants can link together to float. This behavior actually helps this invasive species to survive during floods and to colonize new habitats. (To find out more about fire ants read this post.) Researchers have discovered the mechanisms behind these living floats and found that ants use the buoyancy of air bubbles to float. Linking their bodies together increases water repellent activity. Here is an article on the study by Mlot and colleagues, which was published in 2011 ("Fire-ants self assemble into waterproof floats to survive floods" PNSA 108:7669-7673).

Fire ant.jpg

Air bubbles enable fire ants to float. (Picture is courtesy of Mlot, Tovey and Hu, Ant Laboratory, Georgia Institute of Technology).

I hope this answers your questions!

Steffi Kautz & the AntAsk Team

At a trip today (July 10th) to Boise's MK Nature Center (operated by Fish and Game) our group of preschoolers found a pile of ants. I told them I wasn't sure what they were doing, but I would take a picture and ask someone. So, I found you online! These are just small black pavement ants, I believe. Any insight on what they are up to?

Thank you for your time,


Dear Tricia,

Thank you for sending in the photo of the ants your preschoolers noticed on your recent nature trip. Great find!

The ants are in fact pavement ants in the genus Tetramorium. Although this is a common ant found in urban environments, it can also be found in more natural habitats. Along with the pavement ant, there are likely dozens of other ant species in that same nature reserve, so keep your eyes open the next time you visit the reserve. Close by in the state of Utah over 150 species of ants are known (see the Ants of Utah on

You can read more about pavement ants here in a previous AntBlog post.

Thank you,
Corrie Moreau & the AntAsk Team

hi--this morning we observed a lot of sidewalk ants swarming in our backyard (coming in/out of pavement cracks). there were winged ants (males?) flying up and dropping down periodically. some seemed to be struggling--flying around on their backs before righting themselves. now this evening there is no swarm, but some new piles of debris along some of the pavement cracks that a few ants are tending.

what was going on this morning? any help is appreciated!



Dear Virginia,

Although it is hard to identify the ants without pictures, it is quite possible that they are the common European pavement ant (Tetramorium caespitum), which have become one of the most abundant insects in the Northeastern US. If you want to try to identify them, follow this link to the AntWeb species page for Tetramorium caespitum.

As the winged ants are the reproductive members of the colony, it is possible that the colony you are observing was sending out queens and/or males to reproduce with other nearby colonies. Often, they form mating swarms with queens and males from many different colonies, so if the all the members of the swarm were winged, then it is likely that you were observing a mating swarm.

If there were only a few winged members in the swarm, then it is possible that you were observing a territorial battle between two different colonies of Tetramorium caespitum. These are fairly common on sidewalks and between pavement cracks, and have been documented well by the fantastic photographer Alex Wild. See the picture below for an example of these battles (Photo by Alex Wild).


I hope this answers your questions!


Max Winston & the AskAntTeam


My buddy and I were walking back into our office today and he noticed a brown spot in the grass. Upon closer examination, we realized that it was a giant pile of ants and could not figure out what they were doing. We just wanted to know why they were all grouped up like that and what they were doing. Please let us know if you have any input - it would be greatly appreciated.

Thank you,





Hello Val,

These are the common pavement ant, variously known as Tetramorium caespitum or here at Ant Web (pending publication of research on its classification) Tetramorium species E. Originally from Europe, it is now established across the northern half or so of the US and in southern Canada, in urban areas. It has also made it to another outpost of European culture, in South America, south of Buenos Aires, Argentina! This species is famous for its pitched, but rarely lethal, territorial battles among neighboring colonies and you have found a particularly good example of this behavior.


James C. Trager of the AntAsk Team



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