The common saltbush species on the north side of the Salton Sea is Atriplex polycarpa (D). The one-seeded fruit (utricle) of this species is collected in great numbers by harvester ants. After extracting the seeds underground, the empty husks are piled up outside the entrance to their nests. See following two images.

Pollen-bearing (male) flowers.

Seed-bearing (female) flowers.

The most common ant in southern California is the Argentine ant (Iridomyrmex humilis). According to Wild (2004), this species was originally described in the genus Linepithema by Mayr in 1866; therefore, the proper binomial should be Linepithema humile. It is a small, dark-colored ant about 3 mm (1/8 inch) long that invades homes in search of food and water. They are especially fond of sweets, but will feed on practically any food. They love the yolks of hard boiled eggs and carry minute yellow clumps of yolk back to their nest in endless ant columns. These ants are extremely well adapted to urbanized areas of the United States with mild climates and well-watered gardens. They pose a serious threat to native wildlife by upsetting delicate food webs. They are especially formidable due to their aggressive behavior and the enormous size of their colonies which can literally "team up" with other colonies.

If you live in southern California, you probably have seen endless single file columns of uninvited six-legged guests walking through your home. They follow a pre-marked pheromone "scent" trail initially laid down by scouts who were searching for goodies in your pantry. Although they prefer the outdoor life style, they primarily enter houses for food and water. They are fond of sweets, tuna, syrups (even cough syrup), juices, eggs, dead spiders and rodents, vomit, feces and just about any other organic matter they can find. They are essentially scavengers and they play a valuable role in the natural ecosystem--but preferably in Argentina. In hot, dry weather they often search your home for water, including bathroom faucets and drains. I once followed an ant safari into my bathroom where they were neatly stacking their precious cargo of tiny eggs inside my toilet tank. They also relish the "honeydew" secretion of aphids, and protect their aphid friends from natural predators. In the fall months as the nights get chilly, they once again seek the warmth and shelter of your cozy home.

The first Argentine ants set foot on U.S. soils in the late 1890's, as coffee ships from Brazil unloaded their cargo in New Orleans. Being prolific breeders and constantly on the go, they moved across the southern half of the United States. A single colony may contain 10,000 female workers, and there may be hundreds of colonies around your home; the total number of ants could easily reach a million. Although they cannot sting, they can bite; however, they are only about 3 mm long and their tiny mandibles are too small to hurt humans. But, in the world of insects, these ants are truly a living terror. They are very aggressive and readily overtake other ant species, even ants that are much larger and with powerful stings. Argentine ants are relentless and simply outnumber their adversaries until the enemy colony is destroyed. They even attack paper wasp nests under the eaves of a house, forcing the huge wasps to flee their nests in terror. Even nests of large carpenter bees are no match for these relentless ants. An Africanized ("killer bee") nest probably could not withstand an invasion of Argentine ants. They will also attack bird nests, driving off the mother bird and killing the helpless young. They occupy practically every square meter of my yard in San Diego County and live inside the walls and under my house. One possible redeeming quality about these little warriors is that they may attack dry-wood (aerial) termite colonies in your home. I have observed this Lilliputian massacre in a termite infested table in the Palomar College greenhouse.

Argentine ants have also invaded Europe, South Africa, New Zealand, Japan, Easter Island, Australia, and the Hawaiian Islands. There are no native ants on the Hawaiian Islands, but there are more than 50 introduced species. Some of these are an ecological disaster, and pose a serious threat to indigenous species. In fact, the Argentine ant locally threatens insects that pollinate the endemic silver sword on Haleakala, on the island of Maui.

Most ant colonies are very territorial, and will fight different colonies of the same species. Since Argentine ants in the United States originated from the original colonizers in Louisiana, they are all closely related with very similar DNA. They will accept ants from different colonies as members of their gigantic family. In fact, Argentine ants from different colonies will actually "team up" and attack together in vast swarms. They simply outnumber and overpower their enemy.

Argentine ants have become a serious threat to the coast horned lizard (Phrynosoma coronatum) in southern California. The primary food source for these endangered lizards are native harvester ants, particularly the California harvester ant (Pogonomyrmex). I spent many years observing this fascinating red ant while growing up in San Gabriel Valley, and I can personally testify that it has a painful sting. As of 2006, this large red ant is seldom seen in urbanized areas of coastal southern California where Argentine ants thrive.

Urbanization has certainly been a factor in the demise of California harvester ants, but an even greater factor resulting in the elimination of native ants and coast horned lizards is the aggressive Argentine ant. Apparently the horned lizard is not fond of Argentine ants, and is actually attacked by them in enormous swarms. Colonies of Argentine ants need a damp area to survive, and have not invaded some of the dry habitats where native harvester ants and desert horned lizards (P. platyrhinos) still live. Of course, they can readily colonize urbanized desert areas inhabited by people. Well-watered gardens with stepping stones and concrete slabs provide the ideal living requirements for these ants. In their native Argentina they live under rocks.

Argentine ants are a terrible nuisance in gardens and orchards because they tend and protect scale insects and aphids. They even carry aphids to the tender buds of your prized roses. In return, the ants consume a sweet secretion from the aphids called "honeydew." In addition, swarms of these ants will invade orchard trees, destroying the fruit crop. This is especially serious in figs (Ficus carica) where the symbiotic pollinator wasps are destroyed.

According to entomologist David Faulkner, if you have a 10 x10 foot (3 x 3 m ) patio slab, you could have a million or more individuals and possibly 20 or 30 queens. They get along fine because they're all related to the original colonizers in Lousiana, perhaps from the original gravid (pregnant) female who arrived there. Workers live a month or more as adults, but queens live up to 10 years or more. With other ants, when the queen dies, the one-queen colony dies because no more ants are being produced. With multi-queen Argentine ants, another queen simply moves in and takes over the role of the deceased queen. In fact, a queen from San Diego would be accepted in a colony in San Francisco.

The Argentine ant was introduced into Europe about 80 years ago and has grown into a supercolony that extends more than 3,700 miles (6,000 km). It extends from northern Italy, through the south of France to the Atlantic coast of Spain, with billions of closely-related ants and millions of nests. According to Laurent Keller of the University of Lausanne in Switzerland and his colleagues (Giraud, T., et al. 2002), the European ants are only 28 percent less diverse genetically than those in South America. Keller and his colleagues have proposed that supercolonies developed through a process called "genetic cleansing." In a new territory away from old enemies, Argentine ants prospered. Genetically similar colonies, that could cooperate, wasted less time fighting and were more successful than the others, until a genetically more compatible supercolony emerged.

• Giraud, T., J.S. Pedersen, and L. Keller. 2002. "Evolution of Supercolonies: The Argentine Ants of Southern Europe." Proceedings of the National Academy of Sciences 99 (April 30): 6075-6079. Abstract available at http://dx.doi.org/10.1073/pnas.092694199.

• Torres, C.W., Brandt, M., and N.D. Tsutsui. 2007. "The Role of Cuticular Hydrocarbons As Chemical Cues for Nestmate Recognition in the Invasive Argentine Ant (Linepithema humile)." Insectes Scciaux 54: 363-373. Available online at http://nature.berkeley.edu/tsutsuilab/Torresetal_2007_InsSoc.pdf.

• Tsutsui, N.D., et al. 2000. "Reduced Genetic Variation and the Success of An Invasive Species." Proceedings of the National Academy of Sciences 97 (May 23): 5948-5953. Available at http://dx.doi.org/10.1073/pnas.100110397.

• Van Wilgenburg, E., Symonds, M.R.E., and M.A. Elgar. 2011. "Evolution of Cuticular Hydrocarbon Diversity in Ants." Journal of Evolutionary Biology 24: 1188-1198. Available at http://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2011.02248.x/pdf.

According to Professor Keller and his colleagues, sooner or later, rivalries between colonies in Europe will emerge as genetically distinct groups of ants turn against each other. When encountering another individual, an ant must decide whether this individual belongs to its colony or not. The recognition cues are genetically based odors on the surface of the ant called "cuticular hydrocarbons" (Torres, C.E., et al, 2007; Van Wilgenburg, E., et al., 2011). These contain up to 100 compounds, including n-alkanes, alkenes and methyl branched hydrocarbons. As long as the ants have the same chemical odor they will not fight. Apparently, ants between San Diego and San Franciso "smell alike" because they do not fight. Interestingly enough, a second population in the Catalan region of Spain has a different cuticular hydrocarbon recognition odor because they readily fight with the other European supercolony.

Professor Deborah Gordon and her colleagues at Stanford University analyzed DNA from ants in the Jasper Ridge Biological Preserve and found obvious genetic differences among some of them, suggesting that the ants came from different colonies. Gordon's research raises serious doubts about the existence of a single supercolony running through the entire state of California. The Stanford team questions the notion that Los Angeles ants are descended from the same founding population as San Francisco ants, which live 400 miles away. A more likely explanation, they say, is that California has been infested by numerous colonies of genetically distinct Argentine ants during the last 100 years.

• Ingram, K.K., and D.M. Gordon. 2003. "Genetic Analysis Of Dispersal Dynamics In An Invading Population Of Argentine Ants." Ecology 84 (11): 2832-2842.

I have compared Argentine ants with the "Borg" of Star Trek, a fictional cybernetic race controlled by drones. This is probably not an accurate comparison because the Borg apparently have centralized control by the "Borg Queen." Ant colonies exhibit "swarm intelligence" with the collective behavior of a decentralized system. The individual units (workers & soldiers) are sterile females that operate without a power hierarchy or permanent leader. The queen's role is basically an egg machine to reproduce and perpetuate the colony. The indivuals communicate with each other by the release of pheromones. Extreme warfare in ants arises from a social unity similar to cells in an organism. Cells are recognized as "self" by our immune system because of chemicals imbedded in the cell membranes. Some of these are special proteins (glycoproteins) with unique carbohydrate antennae. Just as foreign bacteria and viruses are recognized as "enemies" by our immune system, ants recognize rival colonies by different pheromones. Simplified diagram of cell membrane structure. This model shows large protein (glycoprotein) molecules embedded in the membrane. Membrane proteins may serve as carriers in which molecules and ions pass through channels in the protein. Glycoproteins may also be associated with cell recognition in which patrolling T-cells and antibodies recognize the shape of membrane proteins as "self" or "foreign." These membrane proteins often contain unique carbohydrate chains (antennae) which are involved in the cell recognition process.

In their native homeland of Argentina, different colonies of Argentine ants are not so friendly to each other because their DNA has developed much greater variation. Neighboring colonies may fight each other, even though they are only 200 yards (200 m) apart. Also there are many native predators in Argentina, including fungal parasites and bacteria. The narrow genetic variability that has kept all the California populations on friendly terms may eventually backfire due to excessive inbreeding. Perhaps some day these ants may not have the genetic variability to adapt to a changing environment.

It is is a known fact that genetically different Argentine ant colonies in Argentina will aggressively attack and kill each other. Closely related Argentine ants (i.e. sisters in the same colony) smell alike because of the same cuticular hydrocarbons; therefore, they accept each other and do not fight. This apples to the supercolony that extends 600 miles from San Diego to San Francisco. Ants from different cities along the way can be placed in a cup ("fight cup test") and they get along just fine. According to Melissa Thomas, an Australian entomologist, Argentine ants have invaded every continent except Antarctica. No matter how many thousands of miles separate individual ants, when two of them are placed together--whether they came from Australia, Japan, Hawaii, or Easter Island--they recognize each other as sisters in the same supercolony.

As I stated above, there appears to be some different opinions among authorites as to the giant superpopulation of Argentine ants in California. A team of researchers at Stanford University state that California has been infested by numerous colonies of genetically distinct Argentine ants during the last 100 years! See Above Paragraph.

But according to David Holway, biologist from UC San Diego, there appears to be more than one genetically different population (colony) in San Diego County, perhaps different introductions from Argentina. In fact, in the city of Escondido, near my home in San Marcos, a battle has been raging between two different "families" or colonies separated by the width of a driveway. The battle is so intense that dead ants have been piling up in the driveway and in the gutter.

The Winter Ant (Prenolepis imparis) Subfamily Formicinae Remarkable Native California Ant With A Potent Chemical Defence Against Invading Argentine Ants

Worker ants of Prenolepis imparis may be able to survive the attacks of Argentine ants. I first noticed these shiny black ants on 3 December 2012 near Palomar College, hence the common name of "winter ant." The thorax (mesosoma or alitrunk) is deeply constricted in center and resembles the shape of an hourglass when viewed from above. These ants are slightly larger than Argentine ants (just over 3.0 mm). According to Trevor R. Sorrells, et al., Department of Biology, Stanford University (2011), winter ants secrete a hydrocarbon mixture that is lethal to Argentine ants, thus providing an effective defense against this invasive species from South America. "Prenolepis workers are more likely to deploy their chemical defense in encounters near their nest than in encounters while foraging on trees. This indicates that P. imparis modifies its behavior according to the value of the resource it is defending. This may be because the production of the secretion is metabolically costly." Please refer to following link in peer-reviewed journal PLOS ONE Volume 6 (4) 2011.

Young workers (repletes) are "overfed" and swell with fat, from which a nutritious glandular secretion is produced that is the main food upon which the year's single brood of workers and alates is reared. After this corpulent stage, the storage workers lose weight and become foragers. The name "false honey ants" comes from the subterranean replete caste, although the stored food is apparently not a sugary (honeylike) solution.

This shiny black ant on Owens Peak superficially resembles the winter ant (Prenolepis) except its first antennal segment (scape) is shorter than Prenolepis (not longer than the head). In addition, it has a distinctive heart-shaped gaster, pedicel with two nodes, 3-segmented club, and a pair of dorsal spines on the propodeum. The name "acrobat" refers to the flexible way that a worker holds its abdomen (gaster) up over the rest of its body.

Although Biosphere 2 was protected from the outside air with a closed air-lock system, it apparently was not impervious to small ants. By 1993 populations of the invasive crazy ant (Paratrechina longicornis) were discovered inside the supposedly closed ecosystems. The crazy ant is named for its peculiar erratic movements. By the late 1990s, virtually all the ants in Biosphere II were Paratrechina longicornis, feeding exclusively on honeydew secretions from scale insects and mealybugs on many of the plants.   See More Images Of The Crazy Ant

Biosphere 2 is a three acre complex of glass pyramids and geodesic domes with self-contained biomes, including tropical rain forest, grassland savannah, and marine ecosystems. Described as a "planet in a bottle," it was originally constructed in the late 1980s and early 1990s. By 1993 populations of the invasive long-horned crazy ant (Paratrechina longicornis) were discovered inside the supposedly closed ecosystems.

The crazy ant is named for its peculiar erratic movements. It is easy to identify with its long legs and very long antennal scape (basal segment of antenna). By the late 1990s, virtually all the ants in Biosphere 2 were Paratrechina longicornis, feeding exclusively on honeydew secretions from scale insects and mealybugs (Order Homoptera) on many of the indoor plants. Biospere 1 is the planet Earth, and its terrestrial ecosystems are impacted by introduced ants. One case in point is the ubiquitous Argentine ant invasion of southern California.

Even with all the safety precautions, including sealed doors and elaborate air-lock system, the Biosphere 2 complex has been invaded by this small, long-legged ant from tropical Asia. It can survive in highly disturbed and artificial areas, including ships at sea. Since it can live indoors with humans, there is no limit to the latitude where it can exist. In fact, it has been reported in human habitats from Sweden to New Zealand, and may be the most widely distributed ant species on earth!

Another South American species of crazy ant in the subfamily Formicinae (Nylanderia fulva), is an aggressive exotic species introduced into the southern and southeastern United States. It is called the "tawny crazy ant" or "Rasberry crazy ant," and is named after the exterminator who discovered it in Texas, Tom Rasberry. Like Paratrehcina longicornis it is called a "crazy ant" because of its random (erratic), non-linear movements. Preliminary studies indicate that supercolonies of this species may be displacing the troublesome fire ant (Solenopsis invicta) and may even be a worse pest. Unlike the fire ant, they don't sting; however, they readily invade homes and even damage electrical equipment.

Because of their reduced or nonexistent eyes, army ants are blind and follow closely behind the ant in front of them. Imagine the following scenario: You are running as fast as you can, following a pheromone scent trail behind your sisters. For some reason your group becomes separated from the main foraging trail. You are blind and must rely on the recognition scent of the sisters in front of you. Eventually a new pheromone trail is laid down, but you are running in a continuously rotating circle. Your situation is critical because you are in an endless loop and will eventually die of exhaustion. This is precisely what happens to army ants in tropical America. See following image and video: See YouTube Video Of "Ant Mill" In Costa Rica.

Return To WAYNE'S WORD Home Page Return To NOTEWORTHY PLANTS Page Go To Biology GEE WHIZ TRIVIA Page Go To The LEMNACEAE ON-LINE Page