Ask an Ant Expert: January 2011 Archives

Dear Askantweb,

There is a group of fire ants congregating on a mound. Please see the attached pictures. They are tightly clinging to themselves like balls of ants. I haven't seen this behavior before and found it quite unusual. When I took the picture it was a warm day after it snowed a couple of days before. The ground was a little wet. Please explain why this happening and provide assistance in order to know what to do, should I spray or use some other type of insecticide to keep them from spreading. I live in East Tennessee and they are new to the area. Any assistance would be greatly appreciated, Thank You. Taylor, Philadelphia, TN



Dear Taylor,

This is an unusual behavior! So much so that we contacted a fire ant expert, Josh King, to help with this post. Here is what he had to say:

"This sort of "clumping" behavior is most commonly seen during flooding when the colony is forced out of their nest by rising ground water. As flooding is not an issue here (it seems), and there is a conspicuous lack of a distinct mound, I suspect that the ants are doing something they normally do on warm days after cold weather - they are moving up to the surface to warm up. The lack of a mound may explain why they are clumping, as they normally gather in high densities in the mound to thermoregulate, but in this case there is no structure, so they are clumping upon one another, which may also increase warming a bit. Sorry my answer could not be more definitive!"

As for getting rid of the ants, please see the following AntBlog post here.

Joshua King (guest expert), Corrie Moreau, & the AntAsk Team


I am an undergrad student from the Philippines and my thesis is about Ant diversity and their possible potential of being bioindicators of disturbance in an area. I would like to ask help from you guys for any related literature about ants here in the Philippines. Anything will help me a lot, be it about diversity, foraging, or other indication studies about ants published. 

Please help me.

Thank you.

Dear Rafael,

Thanks for your question. That's a really interesting topic, and there has been quite a bit of research into the use of ants as bioindicators. I'm not aware of any research that has specifically focused on the Philippines, but I can give you some citations of relevant studies from nearby areas like Borneo (e.g., Bruhl et al. 2003) and Papua New Guinea. It is further away, but some of the best Ants as Bioindicators work has been done in Australia.

But first: Anyone considering using ants as bioindicators, or sampling a large amount of leaf litter ants for any sort of ecological question, should read this book:
Agosti et al., 2000. Ants: standard methods for measuring and monitoring biodiversity
It is available here almost in its entirety for download in pdf form.

A recent paper that deals with statistically sound ways of sampling ants was just published in Myrmecological News:
Gotelli et al. 2011. Counting ants (Hymenoptera: Formicidae): biodiversity sampling and statistical analysis for myrmecologists.

Regarding Philippine ants, there was a very useful revision of the genus Odontomachus in that same issue of Myrmecological News:
Sorger, D.M. & Zettel, H. On the ants (Hymenoptera: Formicidae) of the Philippine Islands: V. The genus Odontomachus Latreille, 1804
Another recent revision is by Zettel (2006) of the genus Pristomyrmex.

Of the few works to be published about Philippine ant assemblages in the past 50 years or so are:
Way et al. 1998
Samson et al. 1997. Ant Diversity and Abundance along an Elevational Gradient in the Philippines. , and this one that might be useful with regards to the negative indicator species described below.

There is also, I might add, an excellent list of ants from the Philippines here and a useful key to their identification here.

That being said, you should try and do as much reading as you can about other case studies in which ants have been used or proposed as biomonitoring tools. For those readers not yet familiar with the "Google Scholar" search tool within Google, it is an excellent supplement to and even substitute for most online literature search engines. Click here for results relevant to this post.

Of the many articles that are retrieved, one of the most useful for justifying the use of ants as bioindicators is by Majer et al. 2007

Perhaps my favorite study on the subject is Anderson et al.'s 2002 Using Ants as Bioindicators in Land Management: Simplifying Assessment of Ant Community Responses. Anderson and colleagues clearly articulate one of the most important things to look for in a biomonitoring protocol: feasibility. "Will we actually have the time and expertise to continue this protocol, or is it so elaborate that we're dooming ourselves to a one-shot deal?" That is a very important question to ask.

In my mind, there are four main styles of using ants (or any other organisms) as bioindicators:

Umbrella species - make sure these species are protected, and all other species will be safe. Their absence should send out warning alarms. This approach is essentially the "Spotted owl" approach that environmental activists in the Northwestern United States used to justify saving big trees. From an ecological standpoint, it makes sense to select species that are very sensitive to disturbance, because that way, if they are safe, everything is safe. The logic of the umbrella species is that you want to take the most sensitive, asthmatic canary with you when you descend down that coal mine. With respect to ants, umbrella species would be tricky to use in a place like the Philippines because many of the most sensitive ants will be undescribed species, and it will take years to establish their identity. However, if there are known rare endemic ants on a particular island, this approach might be helpful, especially in combination with another outlined below.

Negative indicator species (NIS)- Bad Species! No! Go Home!
Negative indicator species should not be there. If you find them somewhere, then something is wrong. In many areas around the world, invasive species are present where ever there is human-caused disturbance. They themselves are also a force of ecological change. Five species of invasive ants (Anoplolepis gracilipes, Linepithema humile, Pheidole megacephala, Solenopsis invicta, and Wasmannia auropunctata) are among the 100 worst invasive species world-wide, and each have been show to change ecosystems in their introduced range. These species are excellent candidates for inclusion in a biomonitoring protocol in an area with many unidentified species, because they can often be unambiguously assigned a taxonomic name and an ecological value. In the Philippines, two out of the five have been reported so far: Anoplolepis gracilipes, Phediole megacephala. Those two and a third, Solenopsis geminata, might make good candidates for use in a negative indicator species biomonitoring protocol. And certainly any of the other ones would be worth watching out for if they were to show up. The satisfying thing about NIS as opposed to umbrella species is that when an NIS appears there are two proactive things you can do: try to figure out what went wrong with the environment to let the NIS in, and try to eradicate the NIS from its new range. When your umbrella species starts to decline or disappears altogether, you're often left with fewer clues and, well, no more umbrella.

Functional groups (at or above the species level)- This is when you look at a bunch of different species in a particular group (say, ants, for example) and check to make sure everyone is there. Or, you look at the average value for some trait of that group, or perhaps make sure that the group displays some ratio of traits. People who study rivers and streams in North America have shown that there are certain taxa, that are usually present when streams are unmodified and unpolluted. Because ants, as a family, display a wide variety of ecological roles, they can also be divided up into functional groups, and a characteristic combination of those functional groups should be present in each ecosystem. Australia has a very strong ant research tradition, especially in applied ecology, and the Australians were the first to follow the stream biologists and apply the functional group concept to ants. You can read more about the functional groups of ants here and here
Unfortunately, the functional group model of ant community composition is based upon the ants of Australia, and Australia's ants, like many of its other organisms, are quite distinctive. So a functional group approach to biomonitoring will not always be productive outside of Australia, unless perhaps new functional groups are established in each new place. Because relatively little is known about Philippine ant assemblages, it might be more productive to use a more generalizable approach, like Negative Indicator Species or fluctuating asymmetry (below).

Assemblage properties (of individuals) - Finally, there are some studies that deal with properties of individual organisms, specifically, asymmetry. Ants, frogs, and people are all pretty much bilaterally symmetrical. However, stress during development can cause slight abnormalities to occur, which make us more asymmetrical than usual. The key phrases for this line of research are "fluctuating asymmetry" and "Developmental instability"
Basically, one could take any group of normally bilaterally symmetrical organisms (even some plants and algae have been studied this way!), and measure the same thing on both sides of a lot of organisms. For insects, good things to measure might be eye width or wing length.

I hope this helps, Rafael. Biomonitoring is a very admirable idea, but difficult to accomplish effectively. Ants are a very strong candidate taxon for use as biomonitoring tools because they are very common in many different environments, and display a wide range of ecological preferences and tolerances. They are also fun and exciting to study! I hope you get a chance to look at some while you're writing your paper!

Jesse Czekanski-Moir & the AntAsk Team

Hi, We have a new little ant farm with Harvester ants. We had a mishap and had to remove the ants to reduce the moisture. During our clumsy transfer a few dead ants ended up back in the farm enclosure. The ants made one tunnel and a ball of white fuzzy stuff is now at the end of it. A couple of legs and perhaps a part of a head are visible around the exterior of it. How did they make this, and what is it?
Thanks very much, Jackie.

Hi Jackie,

Thank you very much for contacting us at AntAsk! Great to hear that you are keeping ants in an ant farm! Without a picture it is hard to say what the fuzzy stuff is, but my guess would be that the ants have formed a waste pile and now a fungus is growing on the dead ant bodies. Does your ant farm smell moldy? And is it still moist in there? It is quite common that ants dispose waste material in special locations to keep the nest clean. Please also read this post. I would recommend that you remove the fuzzy white stuff and carefully wash your hands afterwards. I would also try to further reduce the moisture as fungi usually prefer high moisture. This might further help to prevent the spread of the fungus.

I hope this helps and you will enjoy your ant colony!

All the best,
Steffi Kautz & the AntAsk Team

If and when an ant is moved from one colony to another is it rejected in the new colony? Or it could be taken by other worker ants and brought to the queen ant for decisions. Or does the ant just fit in into the new colony. (Anthony)

Hi Anthony,

Thank you very much for contacting us at AntAsk! This question is not that easy to answer as ants are highly diverse. There are more than 12,500 described ant species to date and many more awaiting description. Each species has a distinct biology and many differ in their response towards an ant which belongs to a different colony. I would say that in the majority of cases, an intruder would be killed by the workers of the resident colony. However, if the intruder is from a colony that is closely related to the new colony, then the workers might not be able to recognize it as foreign and it could sneak in. There are a few ant species, which would accept an ant from a different colony. These ants usually are more primitive in their social organization. Please also read this post. The queen does not take part in the decision process, her job is to lay eggs and to produce pheromones (chemicals), which signalize her dominance over the workers regarding reproduction. The workers perform the task that also involve nest defense against ants from other colonies.

All the best,
Steffi Kautz & the AntAsk Team

I'm a writer, currently working on a children's story which includes an ant anecdote.

In the story, I have six ants carrying a strawberry at a strawberry farm. They carry it about 3 yards (past a child who is watching) to their anthill.

I don't want to include anything in my story that couldn't really happen. Could this scenario happen? If not what would be more likely? Less ants? More? Would they cut the strawberry into tiny pieces before carrying it?

Thanks so much for your help.

Dear Sara,

It is a very nice image! But I have never seen a group of ants carrying a strawberry. If it were very ripe, most ants would simply drink the juice inside of it. Ants tend to put more effort into bringing food back to the nest that is rich in proteins and/or fats. The major exception to this rule is the leaf-cutter ants, who use leaves or other things to feed their fungus gardens. Leaf cutter ants, especially those in the genera Atta or Acromyrmex, would happily cut up a strawberry into liftable pieces and bring those back to their nests, like this picture of an ant carrying part of an apple.

Unlike other ants, these genera of leaf cutter ants need the cellulose in leaves and other plant parts to feed their fungal gardens. The reason most ants bring food back to the colonies is to feed to their larvae; not only do the baby ants need food to grow, they are also the only ones in the colony who can chew and swallow solid food! Adult ants can sip water and other liquids, but they cannot chew food up into small enough chunks to pass through their narrow necks, so they bring large chunks of food back to their babies, their babies chew the food, swallow it, and then regurgitate the partially digested food back into their older sisters' mouths! For this reason, larval ants have sometimes been referred to as the "digestive caste" of the colony.

Leaf cutter ants actually have two "digestive castes": their fungal gardens, which digest leaves and other vegetable matter (in the case of the two genera mentioned above, at any rate), and their larvae, which chew, swallow, and regurgitate the fungus. For ants that don't grow fungi this way (including other genera of "leaf cutters" that actually use insect droppings or dead animals to feel their gardens), they wouldn't bother bringing such a sugary, cellulose-rich source of food back to the nest.

I personally think it's ok to take a few artistic liberties with children's literature. It's not impossible that some Atta or Acromyrmex would carry an entire strawberry back to their nest, and then cut it up there. But it seems much more likely that they would cut it up on site, and then carry it.

Hope this helps!
Jesse Czekanski-Moir & the AntAsk Team


I am battling hordes of very small ants in the walls and under the floor of an old house. They are too small to be carpenter ants or fire ants.

They instantly find any food and get into containers I would have sworn were unassailable. I tried to ID them, but every ant species I thought might be them is said not to sting or bite - and these DO.

They don't raise a huge welt like a fire ant, but it is a very distinct sharp needle-like prick. I haven't managed to stop myself from slapping at them in time to see if it is a sting or a bite. They are quite small (1/12th of an inch, maybe? tops?) and translucent orange in color, with a slightly darker brown dot on the posterior.

I also get very large solid black ants in one room of the house - also from under the floor or through the wall.

Any idea what they are?

Dear Sarah,

I'm sorry to hear about your problem. Normally I enjoy watching ants go about their daily activities, but I have also had some experience with tiny stinging ants like the ones you've described, and I would want them out of my house, fast.

So, first things first, there are some measures you can take before you call the exterminator. We describe how to get rid of ants in your home here.

Second: What are these ants? There are three species I can think of that more or less fit your description that have established reputations for themselves as world-wide pests. They're all stingers, so no need to stop slapping:
Monomorium pharaonis,
Monomorium destructor,
Wasmannia auropunctata.

Monomorium destructor might be the easiest to tell apart from the other two. Its workers are conspicuously polymorphic; that is, when you see a lot of workers together, there will be some that are different sizes. The largest workers will be almost twice as big as the smallest workers, and there will be workers of intermediate sizes. They are usually orange-brown in front with a darker gaster (the gaster is the last major part of an ant's body). Monomorium destructor earned their species name because in addition to having a painful sting, they are very good at chewing through things like plastic bags, clothing, and even the insulation around wires. If you notice a lot of holes in things near where the ants are, then there's a good chance you have these ants.

Under a microscope, it's easy to tell the remaining two ants apart. There are numerous differences, perhaps most obviously the large spines Wasmannia auropunctata has projecting off the back of its mesosoma (the middle body section of an ant). Without a microscope, however, it can be difficult to distinguish the two. If you saw them side by side (or fighting!), you would notice that Wasmannia has a shorter, more square body shape, and is about the same color throughout its body. Monomorium pharaonis has a longer, more slender shape, and it usually has a darker gaster, but on both ants the color can be variable - Wasmannia can have a dark gaster, and M. pharaonis can be all the same yellow-brown color. Wasmannia auropunctata is sometimes called the "electric ant" because of its uniquely scintillating sting. Unless you're a real connoisseur of ant stings, though, it might just feel like another painful annoyance.

Looking at the pictures I linked to on the web might help, but really the best way to get a confident identification of tiny ants is with a microscope or a very, very close picture.

As far as I know, of those three ants only Monomorium pharaonis has been reported from Texas (based on the list published on AntWeb here, and an older list by Wheeler and Wheeler here), but Monomorium destructor and Wasmannia auropunctata are both very good at dispersing with humans. You haven't just come back from a fun trip to a tropical island by any chance, have you? Both Wasmannia auropunctata and Monomorium destructor can be quite common in Southern Florida and the Caribbean.

I hope this helped.
Jesse Czekanski-Moir & the AntAsk Team


I am junior that studies my local ants as a hobby. One question that has been bugging me recently is about  Tetramorium sp. E. I understand that until recently it has been considered to be T. caespitum and introduced from Europe like all other species of the genus except the desert species T. hispidum and T. spinosum. If there are only 2 desert species found in North America, how did they get there and why didn't the genus spread to other types of environments? I was wondering what evidence shows that T. sp E is an introduced species like T. bicarinatum or T. tsushimae, how and when it arrived, and if there is a possibility it isn't introduced.
                                                                                                                                                Joey, Mansfield MA

Dear Joey,

"Where in the world did this come from?" is the basic form of many questions in the field of biogeography. To answer it, scientists use evidence from the fossil record, molecular biology (usually DNA), and the structure and form of living organisms (morphology).

Fossil evidence is often the best, but most ant species don't have a fossil record (although there are many ant fossils, there are not enough to provide back-stories for the more than 14,000 described ant species!). Molecular biology can be very useful in tracing the ancestry of organisms, simply because it provides the most accurate way of re-constructing their family tree. If the most distantly-related members of the group of organisms you're studying all live in the same place, we often assume that place is the origin of the group. For example, the most diverse genus of ants, Pheidole, was shown by Dr. Corrie Moreau to have originated in the New World (North and South America). She used evidence from DNA sequences to show that the most distantly-related groups within the genus were all found there, and almost all of the Pheidole found everywhere else were part of one (relatively) closely-related group. Using this evidence, she reasoned that this is where they must all be from (actually, it was much more complicated than that--she used a lot of statistical analyses and sophisticated software to arrive at that answer. You can read more about it here).

In 1957, myrmecologist Bill Brown published a short piece entitled "Is the ant genus Tetramorium native to North America?"
in which he presents evidence that is more or less a well-reasoned series of anecdotes for the idea that Tetramorium sp. E (which was, at the time, T. caespitum) is not native to North America. For example, he argued that because it is only common in very urban settings in North America, whereas in Europe and Asia it is often found in more "natural" settings, the latter was more likely to be its natural habitat. Although not bullet-proof, this line of reasoning does make sense. As later authors have shown, Brown was probably not actually collecting the same species in all the places he travelled. It would be interesting to go back to his old collections and figure out what species he really got!

In 2006, Dr. Birgit Schlick-Steiner and several colleagues published a paper in which they provided evidence that individuals in what was previously considered Tetramorium caespitum (and the difficult to distinguish T. impurum) were actually members of at least seven different species. They used data from DNA sequences, chemicals found on the outside of the ants (cuticular hydrocarbons) and the way the ants look (morphology). Usually, in situations like this, authors will provide names for the newly erected species. But members of the Tetramorium caespitum group had been described under roughly 50 different names in the past, and the strict taxonomic convention dictates that they have to be assigned the first given name. Rather than attempting to find and re-evaluate all the relevant type material, they decided to simply go with a series of letters. (it should be noted that, at the time of this writing [January 2011], the majority of images of Tetramorium caespitum on AntWeb are actually of Tetramorium sp. E).

This study supported the idea that "pavement ants" aren't native to North America by showing that there were a cluster of closely-related, but distinct species in Europe, and, within that cluster, one very closely-related group in North America. Such close relationships over a very wide geographic area (across the US) strongly suggest a recent introduction. Although it is at a much finer taxonomic scale and grain, this reasoning is analogous to that used in Moreau's study of Pheidole described above.

There are collections of T. sp. E from the United States dating back to the early 1900s, and possibly before, so it was introduced before that, but (I would guess) probably not before the 1600s. Interestingly, there is also a species of ant that doesn't ever have workers and has to live as a nest parasite of Tetramorium sp. E, called Anergates atratulus. The most likely way that this species was introduced was with a whole or partial colony of Tetramorium, perhaps in some construction materials or ballast brought over from Europe. Both species may have even been introduced more than one time. In fact, Schlick-Steiner and colleagues' 2006 study showed DNA evidence of at least two separate introductions.

Regarding your questions about the truly native Tetramorium species in Americas, the desert relatives of the pavement ant, Tetramorium hispidum and T. spinosum are in the same genus, of course, but they are actually quite distantly-related, and have likely been present in North America for millions of years. The idea of a 'genus' is tricky, because it is not comparable in very different groups of organisms. Most of what we think of when we think about different species within a genus are mammals, and have only been separated for 10 million years or less. But really, many insect genera are actually about the same age as the majority of what we call "orders" within Mammalia (both are often around 65 million years old, give or take 15 million years). Thus, just because Tetramorium sp. E was suited for life as a pavement ant in cities across North America, doesn't mean that its very distant cousins are.

How do we know that they're native to North America? The best evidence is that they are distinct, recognizable species that have never been found anywhere else. Actually, for a long time, our native Tetramorium were classified in a different genus, Xyphomyrmex. In addition to the desert Tetramorium present in the US, there are three closely-related species in Mexico (T. bicolorum, T. placidum and T. mexicanum), and although there isn't any DNA evidence to prove it, based on the way they look, the closest relatives of the native New World Tetramorium (also formerly members of the genus Xyphomyrmex) are probably in Africa.

Why are our native Tetramorium in the desert and not in the Great Plains or the Boreal Forest? Well, why are cactuses and road-runners mostly in the desert? It is an unsatisfying answer, and like Bill Brown's paper, mostly based on anecdotes and reasoning, but most species, even when they disperse, tend to be most successful in habitats that closely resemble those of their ancestors (the formal, testable version of this statement is called the "Niche Conservatism Hypothesis"). Thus, most invasive species tend to do well in habitats that closely resemble their own. It is possible that the ancestors of the native New World Tetramorium were blown here, or washed ashore from a desert area in Africa. This may have even happened when the continents of Africa and South America were closer together--we could test that hypothesis with DNA sequence data. Tetramorium sp. E, on the other hand, was from a climate more similar to many of the non-desert areas of the United States, and this is where it has been successful.

Interestingly, we can't entirely rule out the idea that the New World Tetramorium never diversified into other biomes, only to subsequently go extinct, perhaps during an ice age. All we can do is shrug our shoulders and say, well, we have no evidence to suggest that they ever did. And when asked why, shrug our shoulders again and say, dunno, really. They just didn't. When the distribution of a species or group is not due to currently operating behavioral or ecological processes (like natural selection), we call this a(n) historical contingency (there are many other types of historical contingencies, perhaps most famously explored by Stephen J. Gould in his book, "Wonderful Life"). They're fun to think about, and propose explanations for (an activity often called "hand-waving," by academics), but ultimately unknowable, at least with the data and methods we have available today. "How did [Tetramorium] get there and why didn't the genus spread to other types of environments?" Is a really great example of such a question. With more molecular evidence, we could say roughly when they arrived, and where they were likely to be from, but we'll never know exactly what transpired when they dispersed here.

I hope this helps!
Jesse Czekanski-Moir & the AntAsk Team


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