Consider the ant.
Highly adaptable, diverse, and for its size the strongest creature on the planet, ants have lived on Earth for more than 100 million generations; humans for about a hundred thousand. With the proportionate strength of an ant, a man could lift a car over his head; and per body weight, ants have larger brains than any other insect or animal, including you and me.
Ants fill all kinds of evolutionary niches, and their highly organized social structure makes them a formidable force in nature as well as in the nooks and crannies of human habitats, where they can cause considerable trouble. They may be the most abundant of all land animals. Entomologists have identified nearly 15,000 ant species, and calculate the total worldwide ant population this way: If the number of all insects alive at any given moment is one million trillion, then one percent of that total, or approximately ten thousand trillion, is made up of ants. Their combined weight would about equal that of all human beings now alive. In the Brazilian rain forest alone, it’s estimated that the dry weight of all the ants is approximately four times that of all the native mammals, birds, reptiles, and amphibians combined, in that lush and teeming world.
There are tropical leafcutter ants, the infamous fire ant, Carpenter ants, Acrobat and Pharaoh ants; lawn ants, crazy ants, meat-eating ants, odorous ants, and more –many thousands more. All are social creatures, dwelling in colonies of dozens to thousands of their kind. Most colonies consist of three castes: one or more large queens, which lay all the eggs; a few small males, which are produced periodically to mate with the queen(s); and the main host of sterile female workers. New queens and males have wings and mate in periodic flights, after which the male dies and the queen sheds her wings and starts a new colony or enters an established one. The female workers care for her and the millions of larvae she produces in her lifetime, which can last for five years or more; in some ant species, queens can live more than thirty years.
Ant intelligence is –at least to us– a startling and fascinating component of their size and industry. One type of Amazonian ant that nests in a specific tree will inject lethal doses of formic acid (a kind of ant venom) into the leaves of other surrounding tree species, resulting in sections of rainforest where the only living trees are the ones preferred by the ants –similar to the way we create crop monocultures. Weaver ants form chains with their own bodies to make living bridges that allow them to cross wide gaps in the tree canopy. Other ants maintain “herds” of aphids, which produce a sweet substance called honeydew that ants drink. The aphids are protected from predators and moved by their ant caretakers from one plant to another as the host plants are sucked dry –much as we protect, milk, and pasture dairy cows and goats.
And then there’s ant farming by proxy: The cornfield ant waits for humans to plant that season’s corn crop before moving its flock of aphids from knotweed “corrals” to the roots of growing corn, upon which aphids feed –graze, perhaps– thus ensuring a constant supply of aphid honeydew for the ant colony. Cornfield ants are so successful at this that some entomologists think they are the most abundant of all insects –even more abundant than all other kinds of ants.
Ant Pest Particulars
The imported fire ant is probably the most notorious member of the ant queendom, but so far this variety has not migrated from the southern United States and poses no threat to the Northeast –yet. Nonetheless, plenty of other ant species, recognizable to almost everyone, are more than annual pesky invaders of kitchen countertops and fruit bowls –they can wreak real havoc.
For example, Carpenter ants can cause as much damage to wood structures as termites. They don’t eat the wood as termites do, but excavate nest areas in deteriorating wood that has been exposed to moisture. Once established, the colony may extend itself into adjacent, sound wood.
These large black or red and black ants are commonly found in porch roofs and pillars, window sills, and wood that is in contact with soil, such as telephone poles, and even in foam insulation. While their natural food consists of aphid honeydew, plant juices, and other insects, they enter buildings in spring and summer to forage for water and food scraps. But if you observe them indoors in late winter or early spring, they are most likely living in the house. Look for small piles of sawdust, which Carpenter ants deposit outside their nests. To control this ant, the nest must be found and all the infested wood removed or treated.
The Acrobat ant is named for its habit of raising the tip of its abdomen over its head when threatened. The workers are aggressive if disturbed and can sting or bite. In the outdoors they nest in the cool damp of logs, stumps, hollow trees, and leaf litter. Indoors, they will create cavities where wood has been kept damp by leaks or condensation from plumbing fixtures, and they will also excavate in foam insulation. But unlike Carpenter ants, the Acrobat doesn’t attack sound wood. A colony of Acrobat ants in the house might be a nuisance, but it is more often an indicator of rotting or water-damaged wood than actual structural damage from the ants themselves. Eliminating the moisture source generally sends the Acrobat ant packing.
On the other hand, the Pharaoh ant has become a serious pest in hospitals, rest homes, grocery stores, restaurants, hotels, and other buildings. They aggressively seek out a wide variety of food, including jelly, peanut butter, bottled juices, soft drinks, grease, and even shoe polish, and will gnaw holes in silk, rayon, and rubber to get to their next meal. In hospitals, Pharaoh ants have been found inside surgical wounds, IV glucose solutions, flower vases and water pitchers, and even in sealed packs of surgical dressings. They contaminate food and are capable of physically transmitting disease pathogens on their bodies.
Pharaoh ant nests can be small enough to fit in a thimble, in the folds of stored clothing, even between sheets of paper. Often the nests are found in wall cracks and light fixtures or under paving stones, in trash containers and in linen closets. They prefer dark, warm places near hot water pipes and heating tapes, and are harder to control than other ants because of their remarkable ability to disperse. Hundreds of colonies may be present in any given building; if only a few are missed, the ant population will quickly rebound. Pharaoh ants will avoid certain pesticides and can transfer what they learn to nest mates. Thus control of their numbers requires cooperation from everyone in the building and still may take years to achieve.
The Organic Outlook
Despite this human-abode invasive nature, ants are an inextricable part of the ecology, playing for one thing an important role in controlling more harmful insect pests. Inside the home, ants –and spiders –consume flea and fly larvae as well as bed bugs, moths, young silverfish, and subterranean termites –in fact, leaving ants to their own devices around the borders of your house can actually help keep termites at bay.
Outside, ants prey on all these insect species and more (including other ants) as they patrol their territories and farm their aphid flocks. Carpenter ants help decompose dead trees; nesting ants dig up and loosen the soil, increasing its porosity and making it easier for air, water, and plant roots to penetrate; accumulated organic matter in ant nests adds nutrients and improves soil structure.
Thus, we must consider the ant and the wider world in which it dwells, and plan control strategies accordingly, starting with the simplest effective measures. Otherwise, disaster looms all too near.
A profound lesson in the ultimate futility of blanket chemical approaches to pest control was served up by the hand of nature during the 1950s, when the USDA declared war on the imported fire ant and began spraying the pesticide heptachlor over 27 million acres of Texas cropland. The stuff killed fire ants, all right, as well as birds, reptiles, fish, and mammals– including farm animals and pets. Rachael Carson targeted the program in Silent Spring as one of the worst examples of environmental devastation ever wrought. Its ecological repercussions have yet to be completely understood.
In an unusual policy response, heptachlor was replaced with mirex, which the USDA insisted would eradicate fire ants without harming wildlife or farm crops. For sixteen years, 130 million acres were sprayed with this new chemical until biologists managed to convince the government that mirex is a powerful carcinogen that readily accumulates in human fat tissue.
The mirex program ended and the fire ant, as it turns out, went on. Not only did spraying fail to eradicate it, the fire ant population was given an advantageous boost. Since mirex indiscriminately killed all ants, including varieties that prey on fire ant queens, the USDA had inadvertently cleared the field for the invader species. Fire ant numbers quickly bounced back and colonized all the newly vacant niches in the ecosystem. Ironically, since fire ants consume insect crop pests such as the sugarcane borer and the boll weevil, many farmers in the area had considered them bothersome but beneficial. But that was before the unforeseen consequences of USDA spraying campaigns allowed fire ants to spread in droves across the Texas plains.
The upside, if there is one, of the failed mirex program was a renewed interest in learning how fire ants really live, and in discovering how to control them without destroying everything else. A lesson –sadly, not the last one– writ large for us all, to be sure, in the track of the ant.
F.Y.I. – SOURCES
- Journey to the Ants: A Story of Scientific Exploration, Bert Holldobler and Edward O. Wilson, 1994 Belknap Press of Harvard University, Cambridge, MA.
- Spineless Wonders: Strange Tales from the Invertebrate World, Richard Coniff, 1996 Henry Holt, N.Y.
- Ohio State University online Fact Sheet, “Pharaoh Ant” by William F. Lyon, posted 1991.
- Virginia Cooperative Extension online Fact Sheet, “Acrobat Ant,” by Lois Swoboda, posted 2003
- Virginia Cooperative Extension online Fact Sheet, “Carpenter Ant,” by Eric Day, posted 1999.
- “Antidote” by Holly Prall, from the Wisconsin Natural Resources online magazine, last updated 11/16/2007, http://dnr.wi.gov
- Newspaper article, “When Ants Take Over the Kitchen” from the Elmira Star Gazette’s Homes section, 4/29/07.
- A Golden Guide to Insects, Herbert Zim and Clarence Cottam, 1956, Golden Press, New York.