The Allegheny Ant

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Ant mound in Pennsylvania –watch out!

The great outdoors holds an infinite variety of wonders to behold, mostly from a safe distance if the beholders know what’s good for them. Coming upon an anthill as tall as one’s armpit definitely falls into this category. While the infamous imported fire ant hasn’t yet migrated to the Northeast (give climate change some time), the native Allegheny mound ant (Formica exsectoides Forel) is in some respects just as formidable. Its mounds are among the largest and most complex of any field ant in the world, and the Allegheny will, at the slightest provocation, pour out of its nest in great numbers to defend the home territory. Hundreds, even thousands of ants with strong biting jaws and formic acid spray at the ready can swarm up a stick and onto your foolhardy arm in seconds.

And one does not have to deliberately tease the ants to provoke them. Even walking too close to the mounds can trigger their alarm pheromones, as so colorfully reported by unsuspecting hikers who had to sprint to get away from the angry horde. Tuck your pants into your socks, tread lightly, and observe from afar. There are remarkable discoveries in the offing.

Mighty Mound Builders

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Mound workers tending the queen

Aside from the shock and woe they might bring to the human experience, ant mounds are a unique feat of environmental engineering, found throughout the world from temperate zones to the tropics. More than simple excavations in the soil, they are exquisitely designed climate regulators that control interior temperatures for the benefit of workers, queens, and the incubation of all-important eggs and larvae. The mound’s surface functions as a solar collector directing heat inward to the galleries and chambers, which are insulated with layers of grass, stems, pebbles, and even discarded caterpillar cocoons glued to ceilings and walls in precise combinations. Eggs, pupae, and larvae are constantly moved within the tunnels to take advantage of the best conditions of warmth and humidity.

In colder climates ants sculpt their mounds into long, gently sloping surfaces that face south for maximum sun exposure. Such mounds were used for centuries as crude compasses by natives of Alpine countries. Ants will also surround mound entrances with objects such as pebbles or feathers to collect morning dew as a water source for the colony. From them, we could learn much.

Everywhere they dwell, mound ants move more earth than any other animal on the planet. They are crucial for the success of topsoil ecosystems, keeping the soil from becoming too compacted. Where we get into trouble with them is more often than not because we’ve encroached on their turf with our own, considerably less integrated building habits.

The Amazing Allegheny

Platinum Pest ControlAllegheny ants are found in woodlands, bogs, fields, and lawns from Nova Scotia to Georgia and westward into Wisconsin and Iowa. The ant may be red-orange, black, or a mix of these colors, about ¼ inch in length with a distinctive irregularly shaped thorax. Unlike other species, the Allegheny ant has multiple queens, each with a lifespan of three to five months; the all-female workers live two to four. Queens spend spring and early summer laying eggs that will become new workers, new queens, and males whose sole purpose is to fertilize the queens.

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Allegheny ant mound community

Some of these queens and workers periodically break off from the main colony to form new, interconnected mounds in a process called “budding.” Within two years, new mounds can reach a height of three or more feet, penetrate at least that far into the ground, bulge to more than seven feet in diameter, and contain at least 250,000 ants.

At this pace the ants quickly form a community of mounds that encompasses large areas, especially in open, undisturbed meadows. Researchers have found as many as 30 to 60 active mounds per acre. One site near Altoona, Pennsylvania, has more than 70 mounds with an estimated ant population in the millions. Mounds in Missouri have been measured at 42 inches tall and 24 feet wide. Another one in Ohio was 13 feet in diameter and contained 230,000 workers and 1,400 queens. A single nest can remain active for 30 years; a colony for a century.

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Measuring the mound –carefully

Not surprisingly, the Allegheny ant has been a focus of research in America since Colonial times. The first scientific study of the species was published in 1878 by Henry Christopher McCook, a clergyman and naturalist who also wrote books on spider webs, fire ants, agriculture, religion, the infamous Whiskey Rebellion (in which his own ancestors played a key role), and Civil War history. As a young man attending theological seminary in Allegheny, Pennsylvania, and later as a pastor in Philadelphia, McCook spent his summers studying the behavior of spiders and ants –particularly the mound-builders.

The “ant city” from which he drew his observations consisted of more than 1,600 conical nests situated on the eastern slope of Brush Mountain, Pa. The largest of these mounds was fifty-eight feet around the base, twenty-four feet over the top, and forty-two inches in height. McCook plainly admired his industrious subjects, going so far as to develop an ingenious mathematical formula to demonstrate that the collective work effort of one mound’s ant population exceeded by a factor of fifty-seven thousand million the capacity of a hundred thousand humans laboring for thirty years to build the pyramids.

“Moreover,” McCook noted, “a vast system of subterraneous galleries penetrates the earth to unknown depths and distances, requiring labors which in magnitude may well be compared with those which excavated the catacombs of Rome.” His entire paper, Mound-Making Ants of the Alleghenies, is downloadable from and is of value not only for its meticulous details of insect life but for the window it offers on the bygone world of the classically trained, self-educated naturalist.

The problem for us here and now with Allegheny ants is that the species can be a serious nuisance for agriculture, and in pastures and Christmas tree farms and forests. While the ants do not chew wood or swarm inside dwellings (individuals might be seen foraging there, but they aren’t moving in), they have the distinctive habit of destroying all vegetation within a range of 40 to 50 feet around their colonies. They achieve this shadeless, enemy-free zone by biting the plants and injecting formic acid into the wounds. This readily kills grass, flowers, and most trees between two and five years old; given enough time, the ants can even kill large, mature trees. Allegheny ants will also colonize parks and lawns that are edged by meadows or unkempt lots. The resulting bare ground is rendered virtually useless for any other purpose but their own.

And Alleghenies are not easily dissuaded. Digging up the mounds can be risky as well as ineffective. They will move to a new spot or “bud off” if disturbed, and since colonies take several years to develop enough to appear aboveground, there are usually large numbers of them by the time their presence is evident. Regular field plowing or mowing of the affected property may be the only non-chemical way to get rid of them.

The Organic Outlook

On the other hand, the Allegheny ant does no real direct harm to people. Clearly the ants must be removed from tree farms and recreational areas, and children kept away from them, but they don’t invade homes in the way that cluster flies or cockroaches do and unlike fleas and mosquitoes are not a source of pestilence or relentless random insect bites.

In their ecological niche, Alleghenies provide a great service. Their colonies, which can consist of hundreds of thousands of individuals, require large amounts of food for immediate consumption and winter storage. To supply it, the ants scavenge dead insects and kill others, including sowbugs, caterpillar larvae, beetles, and other, more troublesome types of ants. Thus the Allegheny mound ant is an important link in nature’s scheme, holding insect populations in check and acting as a cadaver clean-up crew. 

They also consume the honeydew produced by aphids, scale, and mealybugs. Honeydew forms droplets at the end of these insects’ abdomens, which the ants collect. Like other ant species, Alleghenies keep “herds” of aphids and will defend them from other predators. They play host to certain honeydew-producing beetles by keeping them inside the mounds and rearing their larvae. Mound ants will also tolerate the presence of other insects taking refuge with them during winter months, possibly for the extra heat the visitors provide. At any other time, these intruders would be immediately killed.

Allegheny ants are fierce but not invulnerable. Workers that leave the mound can fall prey to other animals, such as birds and spiders. In fact there are species of spiders that mimic the shape of ants and seem able to live inside the Allegheny colonies without raising pheromone alarms, munching at will on eggs and larvae. Bears, apparently impervious to everything, love to break open the mounds and eat larvae no matter how many thousands of ants swarm over them. Even the bare patches the ants create around their mounds may benefit the whole, opening up the forest floor to sunlight and a someday post-colony regrowth of grasses and flowers.

When all else fails, and the Allegheny ants persist in our lawns and fields, we could always take a cue from the bears and eat them ourselves. Though the practice has gone out of fashion in modern times, humans throughout history
have eaten all kinds of insects. On this menu, ants are apparently a dish chosen largely for therapeutic and psychotropic effects, and are used as such in some cultures as arthritis remedies and to bring on hallucinations and spirit quests. However, there is an actual measured lethal dose of ants –about 1,000 of them, swallowed live, will do you in quite handily, so one should stop after the first couple hundred or broil ’em first.

Usual jokes aside, there are entomologists who believe that insect consumption would go a long way toward solving world hunger and environmental problems. Pharmaceutical companies have been categorizing and researching plants and insects, including the formic ant species, as possible sources for new chemicals and medicines. Today’s nuisance pest could be tomorrow’s miracle cure. Tread lightly therefore not only around the ant mounds but upon the planet in general, with humility and gratitude.


The Ants, Bert Holldobler/Edward O. Wilson, Belknap Press of Harvard University Press, Cambridge, 1990

Journey to the Ants, Bert Holldobler/Edward O. Wilson, Belknap Press of Harvard University, Cambridge 1994

“Mound-Making Ants of the Alleghenies,” Henry C. McCook, The American Naturalist, Vol 12 No. 7, July 1878, downloaded from

“Henry Christopher McCook,” from Wikipedia

“Plymouth Woods Nature Preserve,”

“Allegheny mound Ants:if you step on them, be prepared to step on it!!” by Heidi Boyle, Keystone Wild!Notes, Summer 2006

“Ant Palaces” by Craig Anderson, 2008 Conservation Commission of Missouri

“The Allegheny Mound Ant and its Control” by Brad Smith, extension agent; Joseph Weaver, WVU associate professor of Entomology; Dr. John Baniecki,WVU extension specialist plant pathology,

“Bad Shaman Interview” by Spiros Antonopoulos,