Do Ants Release a Chemical When They Die?
WouterUntil recently, scientists thought that when ants die, they release a chemical to signal to other ants that they are dead. However, entomologists at the University of California Riverside found a different mechanism. They studied the necrophoresis of Argentine ants.
The researchers used a method known as coupled GC-MS to analyze the chemical composition of dead ants. They collected aliquots of dolichodial/iridomyrmecin fractions at different post mortem times. These aliquots were then placed on glass coverslips held under ambient conditions. They detected both compounds within an hour after deposition.
The researchers then conducted bioassays to confirm that the solvent-extractable chemicals on dead ants mediate the necrophoric response. During this study, Argentine ants were found to be highly territorial and vicious fighters. They were also found to release a unique smell when threatened.
When ants die, they release a chemical called oleic acid. The chemical smells like olive oil and is used as a defense against predators. Other ants are drawn to the smell and respond by searching for the dying ant.
The researchers then carried out a study to determine how long chemicals remain on dead ants. The chemicals were extracted from small groups of ants and analyzed by coupled GC-MS. The results of the study showed that a subset of cuticular chemicals disappeared within 15 minutes of death. They also found that pupae from 1-h-old dead ant extracts did not travel to a refuse pile.
The researchers explained that their results suggest that the chemicals that signal death dissipate, rather than increase. The study was published in the Proceedings of the National Academy of Sciences.
