Crematogaster nigriceps

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Nigriceps Ant

Deciding where to nest is very important to the Nigriceps ant, because it has a symbiotic relationship with the swollen thorn accacia bush.  It was first thought that the ant had a mutualistic relationship with the Swollen Thorn Acacia (Acacia  drepanolo-bium), where both species benefit.  However, recently this ant-plant relationship has been considered to be more parasitic .  This tree has huge bulbous swellings at the base of the thorns. 

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Swollen Thorn Acacia

The ants remove the soft pitch inside the bulbous swellings and this prepares a dry, cool home.  The ants prune the tree so that other enemy ant colonies cannot get to the tree.  This pruning also provides the ants with food.  When the branches are cut back, a sugary substance is secreted and the ants use this as food.  The stinging ants protect the tree by swarming out of the nest to attack enemy intruders.  Even though the ants try to protect their residence, the tree cannot bear fruit and often has a difficult time propagating.  The pruning prevents buds from flowering, which leads many to believe the relationship is more parasitic than mutualistic.  The tree is harmed, while the Nigriceps ant benefits.
    The Nigriceps ant is the weakest and least warlike among war ants in this particular ecosystem.  Their survivability is based upon the swollen thorn acacia.  The African environment is too wet or too dry at times for the ants to nest in the ground, so they have to customize a home within this tree.  Competition is fierce and they must struggle to keep away enemy intruders.  Their social colony system is amazingly organized and efficient.  Like other insects, the Nigriceps ant has evolved to survive in its environment and adapt to its surroundings.


McGrawHill Encyclopedia of Science and Technology.  Vol. I.  McGrawHill, Inc., NY.      pp. 725-726.

Nigriceps Ant.

Preston-Mafham, Ken and Rod.  The Natural World of Bugs and Insects.  PRC Publishing     Ltd., London.          pp. 270-272.

Traves, Bridget. The Gale Encyclopedia of Science.  Vol. I.  International Thomson Co.,     NY.  pp.                     247-249.

By Bethany Broadwell
April 15, 2004