Marauding Ants May Have Had Aid

Not long after Christopher Columbus’ arrival in the New World, hordes of viciously stinging ants assailed the island of Hispaniola, pouring into homes and ravaging the Spanish colonists’ newly planted crops of oranges, pomegranates and cassia trees. People had to place the legs of their beds in containers of water to avoid being covered in ants during the night.

Two centuries later, a different plague of ants laid waste sugar plantations in the islands of Martinique, Barbados and Grenada.

But which ants? And why did they strike when they did?

After centuries of mystery, ant aficionado Edward O. Wilson, emeritus research professor of Harvard University, believes he has found the culprits behind these two devastating plagues.

Wilson, renowned for his research and writings on natural history and evolutionary theory, pored through historical documents for physical descriptions of the insects and their habits, then matched them against his knowledge of the region’s ants.

Key clues for the Hispaniola ant emerged from the writings of colonist Bartolome de Las Casas, who described the ants as swarming around the root systems of trees and shrubs, leaving above-ground vegetation undamaged. He also stressed how painful their bite was.

Wilson reported in this week’s issue of Nature that this ant was most likely a tropical fire ant, Solenopsis geminate, which has a sting like the touch of a fine, hot needle. The second was probably the so-called African big-headed ant, Pheidole megacephala.

Since neither of these ants chews up crops, the likely trigger for the ant plagues was the inadvertent introduction of a sap-sucking insect carried into the islands on some crop like a plantain, Wilson said.

The ants protected the sap-sucking insects as they devastated the crops. The ants, in turn, feasted on the other insects’ sugar-rich excrement and expanded to huge numbers. The plagues probably subsided when local predators evolved to eat the sap-sucking insects.

Wilson described the ant plague on Hispaniola as the first environmental disaster of the New World.