Many of the fence lines at Southwood Farm, the site of 30 years of my fire ant research, have grown up in bushes and trees, I suppose because the mower can't reach them just outside the fence, making the fence lines a refuge for interesting plants like Erythrina. In the spring, Erythrina pushes up spikes of scarlet flowers and trifoliate leaves, followed much later by bean pods filled with scarlet seeds (hence the name coral bean). There is something mysterious about the geographic distribution of Erythrina, for the approximately 116 species of trees and shrubs are scattered from the Americas to tropical and southern Africa, Asia, Australia, and many islands including the South Pacific and Hawaii. With such a wide distribution, biologists usually argue that the taxon evolved before the breakup of the supercontinent Pangaea, rafting the descendants to all parts of the modern world, but this doesn’t seem plausible, for the genus Erythrina is much younger than this breakup. The current favorite hypothesis is that the seeds float for very long times (over a year), and that ocean dispersal resulted in the wide distribution. That could certainly explain how they got to Hawaii and all those tiny Pacific Islands so far from continental shores.
At Southwood, Erythrina is not particularly common, but several of these plants made their home in the same wooded fence line where Josh and I sought shade during our "death to fire ants" experiment. This experiment came to life because for over 50 years, ant biologists had insisted that the evil commie, foreign-born fire ant was outcompeting and killing our upright, honest, God-fearing native ants. In fact, in Texas (where else), this was the basis of an official fire ant management program--- y’all be nice to y’all’s native ants, they said, and they’ll “level the playing field,” so that the natives will be able to compete with and knock down fire ant populations.
Cranky biologist that I am, I didn't believe any of it. To test this cranky notion, Josh and I needed to remove (a euphemism for "kill") fire ants from one set of experimental plots and compare the subsequent non-fire-ant populations to a set of controls in which we did not kill the fire ants. As is typical in the southeastern US, the pastures of Southwood Farm east of Tallahassee sustained dense fire ant populations, making them ideal for this experiment.
In essence, we wanted to ask, what would happen to the other species of ants in these pastures if we killed all the fire ants? For a start, how would we know how many ants of each species occupied our plots? Fortunately, estimating the abundance of ants isn’t hard. You sink an array of pitfall traps with a little antifreeze so that the lip is even with the ground surface. Ants going about their quotidian tasks occasionally tumble in and get preserved, and the number of ants captured in these pitfalls tells you the approximate relative abundance of each species.
In establishing a baseline before killing fire ants, our pitfall traps in ten 40 by 40 meter Southwood plots captured many thousands of fire ants, but only a few hundred of several other (mostly exotic) species, along with only a handful of truly native ants. This overwhelming dominance of fire ants was ideal for our experiments because if fire ants were suppressing the other ant populations, killing the fire ants should be followed by a great increase of these other ant species, as well as the possible appearance of previously absent species.
For centuries, people have been killing unwanted ants with a variety of poisons, but we couldn't kill fire ants with poison because no poison was specific to fire ants, and killing all ants would make nonsense out of the experiment. We needed to target fire ants, and only fire ants, for certain death. To do this, we used hot water, lots and lots of hot water, heated in an old oil drum lined with clay, with a 60-foot coil of copper tubing, the drum filled with burning charcoal brought to red heat with an air blower. Water from a 250-gallon tank in the back of a pickup ran through the copper coil to come out near boiling-hot at the other end of this Jerry-rigged contraption at the rate of a gallon a minute. Once the bucket was full, we toted it to the next victim fire ant colony, poked a hole in the mound and, taking care not to pour it on our foot, filled the nest with 5 gallons of hot water. The ants were cooked instantly. Another colony blotted out.
Devastation moved with us on our march from one end of each of the five kill-plots to the other. It was a very bad day for fire ants, and my mind conjured up the Spencer Tracy movie, Bad Day at Black Rock. As we waited for each bucket to fill, we relaxed in the shade of the fence row by the Erythrina, passing the time by coming up with several lifetimes-worth of really great research ideas, untroubled by the palpable clash between the desired and the possible. It was fun.
For 3 years, we killed fire ant colonies twice a year in the five kill-plots, sending several hundred colonies to fire ant heaven. We burned bags and bags of charcoal, each bag sending 44 lbs. of carbon dioxide into the atmosphere, and watched bucket after bucket fill with hot water, the shady fence row and Erythrina at our back. Upon every revisit, any sign of survival in treated colonies was met with another bucket of hot water. By all measures, the fire ant populations in the kill plots took a heavy hit, while those in the five control plots continued with their lives, oblivious.
Hot water treatments reduced the number of fire ants in our kill-plot pitfalls by 65% and the number of large colonies from about 25 per plot to about two. Colonies of all sizes combined dropped from about 30 to 10. Killing had been very successful. Control plots remained unchanged.
Were the non-fire ant species grateful because we had saved them from these red hordes? No, they were not. On the contrary, when it was all over, these other ants that had supposedly been suppressed and oppressed by the commie fire ants didn't even notice they were gone. Neither their abundance nor their species diversity changed, sending another half-century of firmly held belief into the rubbish bin.
We had showed that fire ants and co-occurring ants simply do not compete, the Texas gospel notwithstanding. Their abundance results from processes other than competition. True, when fire ants are abundant, native ants are not, but we revealed this to be a spurious correlation. If you believe this correlation is causation, as has been done for well over half a century, then you would also have to accept that hospitals kill people. After all, if you go into a hospital, you have a good chance of coming out with a tag on your toe. It turns out that both hospitals and fire ants have been falsely accused.
Postscript: Josh and the Water Dragon
I (with Dennis Howard) first used hot water to kill fire ant colonies in 1983, and again in the 90s (with Eldridge Adams) heating the water in a large crab pot or a washtub over a propane burner, but the experiments at Southwood showed that hot water at scale was an excellent, targeted way of killing fire ant colonies for research. Josh eventually moved on to a professorship, but he took the lessons of Southwood with him. One of his first actions was to design and have built a portable machine for heating water in large amounts and dispensing it onto unfortunate fire ant colonies. Thus was born The Water Dragon, a trailer-borne fire ant scourge . We continued to collaborate in a series of experiments in which The Water Dragon was our death-dealing monster. The video below gives a brief overview of how it works. Since this time, The Water Dragon has spawned children, and the whole family has been involved in several experiments that tested the effects of fire ants on endangered species such as the grasshopper sparrow and beach-nesting marine turtles. As with the earlier hot-water contraptions, the key to success has always been that it kills fire ant colonies without damage to the creatures with which they share a habitat.
Chlordane to Heptachlor to Dieldrin to Kepone/peanut butter to Mirex to Ferramicide to boiled water-. the course of scientific progress! Readers should know that Dr. Tshinkel in his magisterial Fire Ants book delightfully documents the 'fire ant wars' with all its ups and downs. Also shown are several color photographs of Southwood Plantation. An indispensable book for the shelves of myrme-philes.
A charming story! Beware 0f insubstantiated prejudices.