Some Stenamma Ants Close Nest With Clay Door-Pebble

Posted on April 25, 2013

Scientists have discovered 33 new species of Stenamma, a leaf-litter ant genus that inhabits moderately humid to wet forests throughout the Holarctic region, Central America, and part of northwestern South America (Colombia and Ecuador). A paper on the newly discovered ants was published here in ZooKeys. A worker ant of Stenamma callipygium, one of the newly described species, is pictured above. A clay bank nest of Stenamma diversum is pictured below.

The researchers found that the nests and habits of Stenamma species are quite diverse, and in some cases unique among ants. The Stenamma ant nests have been found in leaf-litter, logs, rotting branches, under bark, under rocks and in steep clay or mud banks. Some of the species making nests in clay were found using a small clay "door-pebble," to block the nest entrance. The door-pebble is used when the ants encounter aggressive ants, such as army ants.

Dr. Michael G. Branstetter, National Museum of Natural History, Smithsonian Institution, said in a statement, "I hypothesize that like cloud forests, the clay bank habitat is less hospitable to the average ant, and thus provides Stenamma species with a more protected and less competitive environment in which to nest and forage."

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