Harvester Ants

Red Ants and Black Ants

Strangely, ants in general, and harvester ants in particular – seemingly small and humble creatures that live in dark chambers beneath the floors of our deserts – have long stirred the human imagination. 

harvester ants

For instance, in the mythology of the Pimas – a tribe of the northern Sonoran Desert and probable descendents of the Hohokam Puebloan tradition – a solid sphere of ants served as the raw material from which the Creator made the entire earth, according to Natalie Curtis in her The Indians’ Book. 

In the folklore of the Isleta Puebloans – a community of the northernmost Chihuahuan Desert and cultural descendents of the Anasazi Puebloan tradition – Big Red Ants and Little Black Ants rescued Corn-stalk Young Man from a bewitched tree so that he could save his starving village from a crippling drought, according Charles F. Lummis in his Pueblo Indian Folk-Stories.   

In the practices of the Navajos – pastoralists and gardeners of the Four Corners region and linguistic descendents of American Northwest Indian peoples – the harvester ants, or “big pinching ants,” had to be placated by elaborate ritual if someone dared to disturb their mound, according to Stephen Welton Taber in The World of the Harvester Ants. 

In a large body of work by modern scientists – very bright people who try to understand our world – harvester ants have become something of a legend because they raise baffling questions that almost seem to extend into the realm of mysticism. 

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Societal Riddles

In a way that mystifies the human mind, which has the inclination to institute leadership, delegate responsibilities, organize resources and set schedules to carry out tasks, a colony of harvester ants (like colonies of other ant species) operates perfectly well in the absence of any apparent central control or organizing force, according to Deborah Gordon, Ants at Work.  A queen mother, who serves as a well-maintained egg-laying machine rather than a royal sovereign, founds a colony of harvester ants, which may grow to 10,000 to 20,000 individuals.  With no evident guiding hand, worker ants – all female children of the queen – go about the complex business of tending their mother, protecting her eggs, nurturing their baby sisters, pampering reproductive sisters and brothers, excavating and maintaining labyrinthine chambers, harvesting and storing food seeds, grooming themselves and defending their colony. 

harvester ants

In another unexplained phenomenon, all neighboring harvester ant colonies of the same species – with no obvious prior communications, coordination or cue among them – emerge from their burrows on a single climactic spring or summer day each year to send swarms of young winged would-be queens with their winged male consorts swarming into the desert air, on missions to breed and establish new homes.  In some puzzling way, all the colonies know the appointed moment.  While most, including all the males, soon die because of exposure to the desert environment, starvation outside the nurturing colony, or predation by various gluttonous ant lovers, a few lucky females, probably less than one percent, will manage to find new homes and establish new colonies, beginning with tiny burrows they excavate into the soil.  The new queen carries within her the sperm from several different males.

The Ant

Hopefully, a harvester ant, which may belong to any of several black to reddish-brown harvester ant species in the Southwest, will not introduce itself to you with its extraordinarily painful sting.  It can induce, especially among sensitive victims, a long list of discomforts, including, for example, extended pain, burning, hives, swelling, wheezing, sweating, faintness, nausea and piloerection (hair standing on end), according to Taber. 

The sting may make you mad, too. 

Closely related to the wasp and the bee, according to Floyd Werner and Carl Olson, Insects of the Southwest, the typical harvester ant measures about three-eighths of an inch in length.  It has “a basket of long setae on the underside of the head” that it uses to carry soil when excavating and cleaning its nest. 

A colony signals its presence by clearing all vegetation surrounding the entrance to its nest, leaving a barren flat or mounded area – a midden – several feet in diameter.  Earning the name “harvester ants,” foragers collect seeds, especially from desert grasses, which they stash in underground storerooms.  They may also prey on insects, especially termites, if they can find and catch them.  They forego water altogether, depending on humidity within their nest for moisture. 

The Colony

A colony begins fortuitously when one of the few winged and fully-mated females, or queens, to survive an annual flight manages to establish a small burrow, most likely in an open area.  “The first thing [any new queen ant] does,” said William Atherton DuPuy in Our Insect Friends and Foes, “is to tear off her wings, which she never expects to use again now that she had made her marriage flight.”  After digging the burrow several inches in depth, she lays several eggs, her very first, which “become tiny, wormlike larvae, and finally turn into pupae, resembling ants enclosed in a papery case,” said Gordon.  “When an ant emerges from the pupal case [after several weeks] it is an adult and does not grow any more.”  The queen, who will now spend the rest of her life in total darkness, nurtures her first young, all female ants, very carefully, from her own fat reserves.  She may even lick them like a mother cat licks her kittens. 

harvester ants with wings

With an apparent inborn understanding of their respective roles, these ants – much smaller, for some reason, than their successors will be – set up housekeeping.  They forage for seeds.  They care for the next generation, working to make the fledgling colony viable before closing down for the coming fall and winter. 

With the arrival of spring, when the ant community reawakens, the population divides into two groups, according to Gordon.  About three quarters of the ants – all females – will operate primarily in the depths of the nest.  Some of these ants care for the queen, the sole, vital source of eggs for the colony.  Some nurture new larvae.  Others excavate new chambers to accommodate their growing numbers.  Others store food in designated spaces.  Still others maintain the nest, carrying ant trash and excavated dirt to the surface.  Some, apparently, just hang around in case they might be needed.  The remaining quarter of the population – again, all females – stays near the surface of the nest.  Again, by some unknown understanding, maintenance workers tidy up immediately around the entrance.  Patrolling ants inspect the nest midden area, stop and interrogate intruding ants, and set the day’s foraging courses.  The foraging ants typically travel perhaps as much as 30 to 40 feet from the nest in their quest for food, collecting the seeds from perhaps dozens of nearby plant species.  Meanwhile, still other maintenance workers police the midden surrounding the nest entrance.  It appears, says Gordon, that the younger ants perform the subsurface chores, the senior ants, the surface duties.  As ants age, they graduate from subsurface to surface duties.

After about five years, when the colony typically reaches a population of about 10,000, said Gordon, the queen produces the first breeding offspring—the winged would-be queens and their winged male consorts.  In a celebration of renewal, the colony may cast its winged emissaries – called “alates” – to the winds once every year for the nest 10 to 15 years, until the queen dies, signaling the eventual end of the colony since she is the sole producer of its eggs. 

Nest Architecture

As the colony grows and matures, subterranean workers expand the nest, creating an interlocking system of tunnels and galleries, according to Taber, although sometimes, “…part of the nest occupies a dome of earth and gravel that the ants themselves build up from excavated materials and from surface scrapings nearby.  These mounds are the hallmark of the western harvester…”

The workers may excavate several feet in depth, to the caliche hardpan of the desert, producing a maze of tunnels a half inch in diameter and chambers several inches in breadth.  The colony uses the chambers for the queen’s housing, the nurseries, seed storage and garbage disposal.  When workers have to repair tunnels and chambers, they transfer larvae and seeds to other, stable quarters.  The workers may litter the mound at the entrance with the detritus of the soil, including such things as small pebbles, plant matter and, said Taber, even broken glass and nails.  (During surveys of archaeological sites for various institutions, we have sometimes found prehistoric beads and other small artifacts on the mounds of harvester ants.)

The workers build a mound surrounded by a cleared surface for uncertain reasons, according to Taber, but they might construct the feature to – for example – minimize flooding of the entrance, provide a barrier to wildfires or to discourage intrusion of plant roots.  They might even use it as a defense mechanism, denying cover to potential predators. 

Importantly, ants “are the primary soil workers in the Southwest…” said Werner and Olson.  “Their nest-making…aerates the soil, helps retain soil moisture or drainage, and fertilizes and distributes many native plants.”

Defense of the Colony

Although armed with a painful sting, the harvester ant nevertheless faces a host of unintimidated, fearsome enemies, some of them so threatening that the colony has to engage them in full-scale combat. 

While the ant suffers predation by birds, amphibians, reptiles, insects, spiders and other organisms, it must see the horned lizard, the so-called “horny toad,” as a dragon.  The colony that faces a horned lizard feeding on the ants near the entrance to the nest may mount a swarming attack against the menacing ogre.   “A [horned] lizard besieged but determined to stay will remain motionless as dozens of ants crawl over its scaly armor, biting and stinging as they go,” said Taber.  Unfortunately for the ants, the horned lizards have “an immunity or defense against ant venom in the form of a detoxifying substance in their blood plasma…, and when mobbed they simply hunker down with closed eyes until the ants leave.”  The horned lizards then simply resume feeding.  The ant colony may suffer considerable losses to a persistent lizard.  (When I was a youngster, I once caught a horny toad and placed it at the entrance of a busy harvester ant colony in the Rolling Plains of Texas, just to see what would happen.  The grateful creature lapped up ant after ant, presumably to the distress of the colony.)

A harvester ant colony may also have to defend itself against competing and raiding ants of other species or even of its own species.  (I remember seeing a colony of harvester ants at war with a force of invading ants once in the Texas Rolling Plains.  It looked like a seething mass of enraged miniature armies in conflict.)

“When harvester ants fight,” said Gordon, “they grab onto each other with their mandibles and hold on.  Often each ant clamps the other’s petiole, the segment that attaches the abdomen to the thorax…  Sometimes one ant succeeds in breaking the other into two pieces.  Sometimes an ant dies while clamped on to another, but the mandibular muscles of a dead ant maintain their grip though the rest of the ant may break off.  …it is not unusual to see an ant walking around with just the head of its attacker still attached to its petiole.”

Ant Studies

 Because of parallels with the human community, ant colonies have for centuries drawn the attention of human observers, especially the biologists, who have studied such aspects as the insects’ life history, social structure, organization, individual behavior, family relationships, navigational abilities, slaving practices, memory, communications, adaptability, genetics and environmental impacts.  Ants, according to the FOXNews.com Internet site, have even suffered the indignity of having their legs lengthened by stilts or shorted by partial amputation by researchers who wanted to see whether lengthened or shortened strides would alter the insects’ calculations of distance. 

So far, the collective studies have shown, as a Stanford University News Release in the Stanford News Service Internet site said, “An individual ant is not very bright, but ants in a colony, operating as a collective, do remarkable things.” 

That may have been what prompted a very wise fellow named Solomon to say in his book of Proverbs:

Go to the ant, O sluggard; consider her ways, and be wise. Without having any chief, officer or ruler, she prepares her food in summer and gathers her sustenance in harvest. How long will you lie there, O sluggard?

By Jay W. Sharp

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