Ant Worst Enemy
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The Worst Enemy Of Ants Are Other Ants!
With The Possible Exception Of Homo sapiens
© W.P. Armstrong 23 June 2021
      Index Of Ant Genera On Wayne's Word       Ant Genera Photographed By Alex Wild  

Index Of Topics
  1.  Dead Ant Species Found In Forelius mccooki Midden
  2.  Ant Massacre At Walnut Grove Park, Twin Oaks Valley  
  3.  Gaster Wagging In Native Fire Ants On Owens Peak
  4.  Ant Massacre On The North Side Of Owens Peak
  5.  Two Miscellaneous But Deadly Ant Encounters
  6.  Genetically Different Argentine Ant Colonies
  7.  Army Ants Dedicated To Raiding Other Ant Nests
  8.  Ant Attacks In Cave Creek Canyon, SE Arizona
  9.  Just Outmaneuver Other Colonies Without Fighting

  1. Forelius mccooki in bridle path near my home in Twin Oaks Valley, San Diego County pile dead ants in middens (graveyards) near their nest entrances. In fact, I have found some of my most interesting ant species of Twin Oak Valley in these middens.

Forelius mccooki nest and midden in Bridle Path of Twin Oaks Valley, San Marcos. The midden consists of ant and other arthropod body parts (mostly heads) resembling a pile of pepper grains near their nest entrance. See following image for remarkable number of species found at this site:

14 species in above image found in Forelius mccooki middens and in pitfall traps on bridle path near my home. This is the greatest ant diversity in a relatively small area in all of my ant expeditions since retirement from Palomar College! A: Solenopsis cf. amblychila queen, B: Pheidole cf. californica major & minor workers, C: Solenopsis molesta queen, D. Cyphomyrmex wheeleri, E. Hypoponera opacior, F. Dorymyrmex insanus, G. Strumigenys cf. rogeri, H. Strumigenys membranifera, I. Linepithema humile, J. Forelius mccooki, K. Cardiocondyla mauritanica, L. Solenopsis xyloni, M. Brachymyrmex patagonicus, N. Strumigenys louisianae. A 15th species, Forelius pruinosus (not shown in above image), was discovered 11 June 2020.

  Ants Of Twin Oaks Valley, San Diego County  

The following image shows nest entrance and minute, fast-moving, Forelius pruinosus surrounded by the dead bodies of southern fire ant major & minor workers (Solenopsis xyloni). My hypothesis is that the red & black fire ants were killed by the tiny orange-colored Forelius. Adding proof to my hypothesis are my observations of the Forelius in the blistering heat of summer, dragging the dead fire ant bodies to the graveyard pile (midden).

Minute, fast-moving Forelius pruinosus (upper half of image) and piles of dead fire ants (Solenopsis xyloni). This species of fire ant is native to arid regions of the southern and western United States. It is not nearly as troublesome as the infamous imported fire ant (S. invicta) native to South America. At a nearby bridle path in Twin Oaks Valley, there are middens containing a variety of insect body parts (mostly ants) near the nest entrances of Forelius mccooki.

The following image shows close-up view of massacred southern fire ant major
and minor workers (Solenopsis xyloni) at Walnut Grove Park in Twin Oaks Valley.

3. Clash Between 2 Ant Species Over Crumbs From My Nature Valley Granola Bar

Southern fire ant (Solenopsis xyloni), native to arid regions of the southern and western United States, and close relative of the infamous imported fire ant (S. invicta). The latter species is native to South America and is a serious insect pest in many tropical and temperate countries of the world. Our native fire ant is a polymorphic species with two sizes of workers called majors and minors. The minor workers are only about 3.0 mm long (slightly over 1/8 inch). Major workers are twice as large. Although they are small they have a potent sting, especially if they get you between the fingers. When disturbed the workers exhibit a phenomenon known as "gaster wagging" where they raise and vibrate their abdomen. They are aggressive little ants, but have been annihilated in many urbanized areas of southern California by the Argentine ant (Linepithema humile).

A clash between native southern fire ants (Solenopsis xyloni) and orange desert ants (Forelius pruinosus) at the summit of Owens Peak (3 Aug 2013). The ants were attracted to my Nature Valley granola bar that I pulverized and placed on a metavolcanic boulder. Some of the fire ants have their gasters raised and stingers exerted with drop of venom at tip. Vibrating (flagging) their gasters (gaster wagging) released venom into the air like an aerosol mist and repelled the orange fire ants (Forelius). I watched the fire ants slowly force the Forelius ants away from the food source. The Forelius quickly backed away from the fire ants and retreated to another area of the boulder. See following video: Please wait about 6-7 seconds for video file to load, the wait is worth it!

  Southern Fire Ants Vibrating Their Gasters Uploaded To YouTube (22 MB)  

Note: Shortly after the above video was taken, the smaller, orange Forelius ants came in droves to the boulder and eventually overwhelmed the fire ants, forcing them to retreat into their crevice entrance. Apparently gaster wagging on this day just wasn't enough to repel the foraging Forelius. I did not observe any ants making physical contact or biting each other. The fire ants were simply forced to retreat by the sheer numbers of faster moving Forelius. I guess the Forelius were more interested in the abundant food source than fighting with the fire ants.

Deby Cassill and her colleagues have published a fascinating article about gaster wagging in the fire ant Solenopsis invicta. They even compare the movements and positions of ants with dog and human gestures: "Postures displayed by fire ant workers are equivalent to those displayed by canines and humans. (a) Alerting family members of an invasion (respectively, emitting a chemical pheromone; vocalizing in the form of barking; vocalizing in the form of yelling, bugles or sirens). (b) Aggression in the form of a physical attack (respectively, stinging; biting; punching). (c) Call for help when buried or injured (respectively stridulating; whimpering; calling for help). (d) Expression of pleasure when interacting with young family members (respectively, abdominal wagging; tail wagging, arm rocking)."

Deby Cassill, Krista Ford, Lieu Huynh, Daniel Shiffman, and S. Bradleigh Vinson. 2016. "A Study On Abdominal Wagging in the Fire Ant, Solenopsis invicta, With Speculation On Its Meaning". Journal Of Bioeconomics Vol. 18, Iss 2: 159-167. Click Here To Read and/or Download Article

4. Ant Massacre On Owens Peak

Pheidole vistana worker carrying dead field ant (Formica moki) into its nest entrance. The debris near nest entrance was littered with insect body parts, mostly the heads and gasters of F. moki, a common ant on Owens Peak (see next image).

Above image shows a sample of ant body parts collected near a big-headed ant (Pheidole vistana) nest on Owens Peak. There was apparently a battle with nearby field ants (Formica moki). Some Pheidole lost their heads, but based on the ratio of body parts, presumably the Pheidole colony was victorious. Undoubtedly, the big-headed major workers (soldiers) played a valuable role in this victory!

5. Two Miscellaneous Ant Encounters

Resistance is futile when fighting Argentine ants. In the above image, an unfortunate fire ant major worker (Solenopsis invicta) is hopelessly overwhelmed by three Argentine ant workers. I was attempting to carefully photograph some imported fire ants (S. invicta) at my home, being very careful not to let any escape; however, they were quickly discovered and annihilated by my resident Argentine ants (Linepithema humile).

  Imported Fire Ants In San Diego County  
Many Imported Fire Ants In Indio, CA

6. Genetically Different Argentine Ant Colonies Found In San Diego County

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 applies 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; however, not everyone agrees with this conclusion, particularly in California.

As I stated above, there appears to be some different opinions among authorities 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!

New Studies At Stanford University Dispute The Single Supercolony Theory

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.

According to David Holway, biologist from Univ. of California, 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 a battle has been raging between two different "families" or colonies separated by the width of a driveway. According to some reports, the battle was so intense that dead ants were piling up in the driveway and in the gutter!

The following article about an Escondido Argentine ant battle by Dave Downey appeared in The San Diego Union Tribune< Dec. 10, 2006: "UCSD Study Says Argentine Ants Very Territorial."

ESCONDIDO -- It wasn’t hard for scientists to find the border separating two ant colonies. “You’d drive up and, before getting out of the car, you’d see the piles of dead ants,” said UC San Diego ecologist David Holway, lead author on a new study of Southern California’s Argentine ants, in a recent interview.

Melissa Thomas, a teammate of Holway’s on the field work and now a postdoctoral fellow at the University of Western Australia, said in a statement that 15 million ants died during a six-month observation period in 2004, along a battlefront that meanders through Escondido neighborhoods west of Interstate 15 and along the western edge of Lake Hodges. Melissa Thomas set out to find the border between the two colonies, and was able to trace it to the driveway of a home in Escondido, CA. The border of the supercolony’s empire lay on the left side of a driveway—clearly defined by a pile of dead ants which spilled out onto the curb, drawing a distinct boundary between the two sides of the driveway. Despite the carnage, the colonial boundary remained largely intact, Holway said. “It was sort of akin to a World War I battlefield -- trench warfare, with a lot of mortality and not much movement,” he said. Escondido is the border between an enormous colony of the non-native dark brown ants that runs the length of the California coast and a smaller one concentrated in the Lake Hodges-Rancho Bernardo-Escondido area, he said. The two are among five colonies known to exist in Southern California, including a small one that occupies a campground at Lake Skinner east of Temecula. Holway said the Southwest Riverside County colony is 100 yards across and confined to a stand of sycamore, pepper and eucalyptus trees.

In contrast, the coastal colony extends for 600 miles. “We think there is a single supercolony that extends all the way from the Bay Area to San Diego,” Holway said. “If you take ants from San Francisco and put them with ants from Los Angeles, they probably won’t fight.” But expect a fight to the death if you put ants from that enormous coastal colony together with ants from Lake Hodges in the laboratory. Holway said the study, published in the December issue of the journal Molecular Ecology, was the first to document through field observations the Argentine ant’s intense territorial aggression. He said the study revealed a strong tendency to fight genetic strangers and a strong resistance to interbreeding, which explains why colonies have maintained different genetic personalities despite continuous confrontation along borders for decades.

The newly emigrated colony of ants poses the biggest threat to the supercolony thus far. Researchers from UCSD are continuing to study the growth of these opposing Argentine ant colonies and the future of the supercolony. Is the reign of the supercolony coming to an end? The newly emigrated colony of ants poses the biggest threat to the supercolony thus far, putting the future of the world’s most powerful colony of super ants at stake. Only time will tell whether the ants will learn to get along or whether they will destroy one another. Or will the clashes between genetically different colonies reduce the dominance of Argentine ants in southern California over other ant species like observations by mymecologists in Argentina.

This remarkable Argentine ant battle between genetically different colonies between Lake Hodges and Escondido (San Diego County) is described in more detail in chapter 16 of Adventures Among Ants: A Global Safari With A Cast Of Trillions by Mark W. Moffett (2010), University of California. Press, 280 p.

7. Eyeless Army Ants (Neivamyrmex) Dedicated To Raiding Other Ant Nests!

For the past 4 years I have searched for this genus near my home in San Marcos, California. They have been collected in traps In San Diego and Orange Counties and throughout Arizona. On January 30, 2016, I looked under a rock on the west slope of Superstition Mountain, Arizona and noticed some minute yellowish or amber-colored ants without eyes. The smallest workers were about 1.5 mm and the largest were about 2.4 mm. I was expecting larger ants for this genus. Army ants typically form temporary camps (bivouacs) instead of permanent nests.

The army ants were bivouacked under the rock in foreground (white arrow) on 30 January 2016. Two days later there was no sign of them at this location.

Army ant worker (Neivamyrmex) from under a rock on Superstition Mountain. According to Neivamyrmex authority Gordon Snelling (Personal Communication, 26 Jan. 2017), it is N. leonardi!

  Army Ants In The Superstitions Of Arizona  

8. Ant Attacks In Cave Creek Canyon: Extreme Southwestern Arizona

Acrobat ants Crematogaster attacking a bombardier beetle (Brachinus).

Honeypot ants (Myrmecocystus) and a solpugid in a fight to the finish. I found them in this position in Cave Creek Canyon. This battle was not staged!

9. Sometimes Ants Just Outmaneuver Other Colonies Without Fighting!

A group of long-legged ants (Aphaenogaster cockerelli = Novomessor cockerelli) have entered a swarming mass of harvester ants (Pogonomyrmex) and are carrying away their piece of Nature Valley granola. The fast-moving Aphaenogaster are taking the granola to their nearby nest. Although I have seen these long-legged ants described as the "cowardly lions of the ant kingdom," I'm not sure this description is appropriate. The Pogonomyrmex are very powerful ants with a painful sting. The Aphaenogaster appear to easily outmaneuver the Pogonomyrmex with their long legs. They are able to lift up the granola chunk and run using teamwork and precision coordination. They can even run over the dorsal side of the Pogonomyrmex.

This group of long-legged ants (Aphaenogaster cockerelli = Novomessor cockerelli) are running away with a large chunk of Nature Valley granola placed near the entrance to a Pogonomyrmex nest. The Pogonomyrmex (red x's) appear to be outmaneuvered by the fast-moving Aphaenogaster. The Aphaenogaster use precision teamwork and coordination to carry the granola chunk. They rotate in clockwise motion as the travel back to their nest. In fact, they are used in robotics research at Arizona State University.

  Aphaenogaster (Novomessor) At Superstitions In Feb 2013  

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