Barry’s Gleanings: “Ants In Your Plants”

“Should someone point out a “bull’s horn acacia” to you, stop and have a close look at this thorny shrub.  Between 4 and 10 feet tall, this acacia has branches along which are pairs of reddish spines that look like miniature replicas of a Texas steer’s horns.  Hence its name.


The Bull-Horn Acacia

Image from: <,_the_Bull_Horn_Acacia_(10078435473).jpg>

Of the many relationships which have evolved between tropical ants and plants, that of the bull’s horn acacia and its stinging ants is one of the most curious.  It is also one of the most dramatic examples of tropical co-evolution between species.

With some caution, shake the end of a branch.  Ants burrow into the end of the spines (sot ice the tiny hole), excavate the inside of the branch, and set up a colony where they rear their young and go about the business of being ants.  When the plant is disturbed, as in the case of your shaking the branch, the pugnacious ants charge aggressively from the spines, stingers armed and ready to defend their acacia host.  It would only take one nasty sting to convince you that this unusual defense system works. [The sting feels like a “staple to the cheek”].


Bull-horn acacia stinging ant

Image from: <;

In addition to repelling would-be grazers, ranging in size from caterpillars to cattle, the ants manicure the ground around the acacia, keeping it clear of sprouts from other plants which might deprive their host for living space in a tropical forest containing 1,200 species of trees and countless other plants.


Stinging ants on a bull-horn acacia

Image from: <;

And the acacia is appreciative.  Not only does it shelter its guardian ants, it also feeds them.  Tiny, sausage-shaped bodies hang from the ends of the leaflets.  Loaded with sugar and protein, they are harvested by the ants.

[You’ll see other ants in a tropical jungle]

On the forest floor you’re almost sure to spot trails carved by leaf cutter ants as they march throughout he jungle in search of tender leaves to attack.  Their trails are veritable highways of activity.  Imagine thousands of people walking home on the highway, each rushing along, carrying a 4 foot by 8 foot sheet of green plywood overhead, and you have the concept of these ants.  Leafcutters are amazingly industrious insects.  They can completely denude a full-grown mango tree overnight, carving circular slabs of leaf about half an inch in diameter, hoisting them overhead and marching down the tree trunk back to the hive, which may be perhaps a half mile away or more.


Leaf-cutter ants

Image from: <;

Several highways lead to their hive – often around the buttress roots of a large tree.  Hives of over 100 square meters, 2 meters deep in the forest floor are not uncommon.  In these hives, millions, perhaps billions, of ants chew the leaf fragments, mixing them with nutrient-rich saliva, into a gruel.  From this gruel the ants grow and harvest mushrooms which provide their food source.


Leaf-cutter ants – on the move

Image from: <;

Large ant colonies can cut and process nearly one hundred pounds of leaves per day.  During the decades long life span of an ant colony, tons of vegetation decompose and are worked back into the forest floor.  Constant rain and heat rapidly degrade tropical soils, and so the vast storehouse of nutrients and compost from the ant mounds create a rich oasis in the soil, who, without the busy ants would be nearly sterile” (257).


Leaf-cutter Ant mound

Image from: <;

Essay from: Insight Guides Costa Rica, ed. Dona & Harvey Haber, London: Houghton Mifflin.

Nature is amazing!  What are ants doing where you live?   Aloha, Amor y Luz, Renée


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About reneeriley

Our blog was begun as a way to share our experiences in China. From August 2010 to July 2011, my husband, Barry Kristel, and I were at our University of Hawaii Maui College sister school, Zhejiang Agriculture and Forestry University in Lin'an, China, a city considered rural because it has only 500,000 people! We had a wonderful time. Then in February 2012, we returned to teach this time at our other sister school, Shanghai Normal University, in a city of over 21 million people. We've made many discoveries. Did you know that now Chinese girls, at least the ones who go to university, for the most part feel they are luckier than the Chinese boys? Did you know that Shanghai saved over 20,000 European Jews during WWII? Do you know how Chinese university students would deal with problems that come up in Dear Abby letters? What's it like to be on the Great Wall of China? Do you know how many Chinese girls had their feet bound and why? And we have recipes from many of the places we've visited. Among others, you can find instructions on how to fry cicadas from one of my ZAFU students and how to make chocolate-Kahlua waffles from my brother Mike in Gainesville. You can also look back to our earliest entry to see what we experienced in Oaxaca, Mexico, in 2006 during the mainly peaceful six months of protest until the Mexican government sent in the troops. Between our stays in China, Barry and I have been on the Mainland U.S. visiting family, friends and Servas hosts as we traveled home to Maui. We share those experiences too. Welcome to our blog! Aloha and Zài Jiàn, Renée and Barry

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