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.
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”].
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.
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.
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.
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).
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