How ants identify dead nestmates

Washington, May 6 (ANI): A dead ant is usually identified by its nestmates and removed from the colony, thus limiting the risk of colony infection by pathogens from the corpse. But how the news of a resident's death is communicated among the nestmates has not been clearly known to date.

For a long time, entomologists have thought that dead ants release chemicals created by decomposition (such as fatty acids) that signal their death to the colony's living ants.

But, now, UC Riverside entomologists working on Argentine ants provide evidence for a different mechanism for how necrophoresis - the removal of dead nestmates from colonies - works.

They have said that all ants, both living and dead, have the "death chemicals" continually, but living ants have them along with other chemicals associated with life - the "life chemicals."

When an ant dies, its life chemicals dissipate or are degraded, and only the death chemicals remain.

"It's because the dead ant no longer smells like a living ant that it gets carried to the graveyard, not because its body releases new, unique chemicals after death," said Dong-Hwan Choe, the lead author of the research paper.

"There is no mistaking that it is the dissipation of chemical signals associated with life rather than the increase of a decomposition product 'death cue' that triggers necrophoric behaviour by Argentine ants," he said.

The researchers used analytical chemistry techniques to identify the "signals of life" in the Argentine ant: the chemicals dolichodial and iridomyrmecin.

"These chemicals, or compounds similar to them, are found in numerous ant species that display necrophoresis. Therefore, these ant species also are likely to have necrophoric behavior triggered by the decrease or absence of chemical signs of life, rather than by cues associated with death. We plan to research this next," said Choe.

He added that dolichodal, iridomyrmecin, or similar compounds are found also in other insects, such as thrips, stick insects, aphids and rove beetles.

"Understanding the exact mechanism of ant necrophoresis will help researchers develop a more environmentally friendly pest management strategy by which we can achieve results with smaller amounts of insecticide," Choe said.

The study has been published online in the early edition of the Proceedings of the National Academy of Sciences. (ANI)