Arizona Ants

Ants are a critical component of the earth’s terrestrial ecosystems.  They consume and break down large amounts of material, they control the populations of numerous species, and they provide food for many others.  For instance, ants make up 40% of the diet of the Northern Flicker, a common Arizona bird.  Despite being small and not so visible, ants account for 15% to 25% of all animal biomass on our planet’s land surface—far more than any other animal group.

So how much do the ants weigh?  Using guesstimates from the references I made assumptions that the average ant weighs .004 grams, and that there are 1,000,000 ants per human.  Thus, the earth’s ants weigh around 21 billion tons (I didn’t try to use dry weight).

Not to be beaten by little bugs, however, humanity is increasing its weight at a rapid rate.  Issac Asimov once estimated that if our numbers continued to grow at the 1970’s rate of 2% (doubling in 35 years), the mass of humanity would match that of the whole planet in about 1500 years (Asimov 1975).  Probably no ants (or any other animal) could survive that.  Of course, our birth rate is declining, and even though our life expectancy is increasing, doubling our numbers will take longer and longer.  If we assume that the average person weighs 120 pounds, our species currently weighs 420 million tons.  If we double every 100 years, and if we do not destroy any ant habitat (OK, that is not a reasonable assumption.  Nevertheless…), it will take 600 years for us to become heavier than the ants.  After that, we get ahead and stay ahead.

The photo shows Myrmecocystus navajo, a member of the Formicinae subfamily.  This one was collected in Yavapai County, Arizona.  The photo may be by Barry Bolton, but it could be by Stefan Cover or Bob Johnson.  It is from the AntWeb website.

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Arizona has 318 ant species, more than any other U. S. state.  Ants are found from the lowest desert areas to near the tops of the highest mountains.  Harvester Ants (Pogonomyrmex, Messor, and Pheidole) are most abundant in warm desert areas.  Carpenter (Camponotus) and Wood Ants (Formica) are more common in cooler uplands and mountains.

Some ants are quite secretive, and either hide or camouflage their nests.  Many ants have a painful bite or sting, but some use other means of defense.  Once while studying ants near Red Pine Mountain, my friend Ray Turner was using an aspirator to capture ants from a camouflaged Formica nest when he suddenly began gasping and momentarily could not catch his breath.  Ray was nearly overcome by the formic acid odor released by the frightened ants.  Some birds place these ants in their feathers to repel parasites.

According to Stefan Cover and Bob Johnson (www.antweb.org/arizona.jsp), 12 of Arizona’s ant species are introduced, but none of these are considered to be problems.  Fire Ants from South America (Solenopsis invicta) have been found in Arizona, but the only known colony has been eradicated.  Fire Ants are highly destructive.  They form large colonies that displace other ants, alter habitats, and consume native animals and their offspring (Arizona-Sonora Desert Museum).  Edward O. Wilson once stuck his hand in a Fire Ant nest to observe the response.  He was stung more than 1,000 times.

Fire ant stings are reported to be quite painful, but according to Justin O. Schmidt (1990), they are only “mildly alarming” in comparison to some others.  For instance, he describes the Bullet ant sting as “Pure, intense, brilliant pain.  Like fire-walking over flaming charcoal with a 3-inch rusty nail in your heel” (quoted in Wikipedia in the article on the “Schmidt Sting Pain Index”).

The Ants (Holldobler and Wilson 1990), Ant Ecology (see Alonso 2010) and the novel, Ant Hill (Wilson 2010) provide extensive information about ants.  Don’t miss the article by Berenbaum (2003).  It gives an in-depth discussion of the pain caused by ant stings, and it is a delightful example of creative nonfiction.  Antweb provides photographs and field guides for Arizona ants.

Ants, like some wise people, eschew cold weather.  While they are out and about next summer we can discuss collecting, identifying, and photographing them.

Conservation status

There would be enormous costs to our planetary ecosystems if ant habitat continues to be lost to human development.  Some scientists have convincingly argued that ants should be at the center of conservation concerns.  Perhaps because of their vast numbers and ubiquity, ants have, in fact, been given relatively little attention.  In a recent article on ant ecology, Leeanne Alonso (2009) discusses the approaches that need to be taken for effective ant conservation.  As Wilson points out in the forward, however, “We have only begun to explore the full impact of ants on the natural ecosystems of the planet…” (viii).

References

Allred, D.M.  1982.  Ants of Utah.  Great Basin Naturalist 42:  415-511.

Alonso, L.E.  2010.  Ant conservation:  Current status and a call to action.  Chapter 4 in L. Lach, C.L. Parr, and K.L. Abbott.  Ant Ecology.  Forward by E.O. Wilson.  Oxford University Press, New York, NY.  409 p.

Asimov, I.  1975.  Science past–science future.  Doubleday, Garden City, New York, NY.  346 p.

Antweb:  www.antweb.org/arizona.jsp. Principal authors:  Stefan Cover and Bob Johnson.

Arizona-Sonora Desert Museum:  http://www.desertmuseum.org/invaders/invaders_fireant.php.

Berenbaum, M.  2003.  A Stinging Commentary.  American Entomologist 49: 68-69.

Holldobler, B., and E.O. Wilson.  1990.  The ants.  Belknap Press, New York, NY.  746 p.

Johnson, R.A.  1996.  Arizona ants.  Arizona Wildlife Views, June 1996: 3-5.

Schmidt, J. O. 1990. Hymenoptera venoms: striving toward the ultimate defense   against vertebrates, pp. 387–419 in D.L. Evans and J.O. Schmidt, eds., Insect defenses: adaptive mechanisms and strategies of prey and predators.  State University of New York Press, Albany, NY.

Wilson, E. O.  2010.  Ant Hill.  Norton, New York, NY.  382 p.

Checklist

The field guides provided by AntWeb can be used as checklists, but the one below is more compact because it is merely a list—no help with identification.  It does sort species into subfamilies.  Many species occur in the rich southeastern Arizona desert and uplands far from the Agua Fria River Basin.  Probably half the species in the list below do not occur in the Basin, but I could not find any lists for any region smaller than the state.