How Ants and Other Insects Handle Their Dead

Ants carry their dead out of the nest. Honeybees do something similar. People have long described this as a funeral or a cemetery. Scientists have found a more practical explanation.

What is necrophoresis?

The removal of dead nestmates from the nest. The word was introduced in 1958 by E. O. Wilson and colleagues, according to a review in the International Journal of Biological Sciences. Early naturalists had already described the behavior in anthropomorphic terms, such as “funerals” and “cemeteries” in honeybees and ants. Serious study of it began with Wilson’s team in 1958, which identified a chemical cue in two ant species.

What triggers it?

Chemistry. Wilson’s team found that oleic acid, a fatty acid that builds up in dead bodies, prompted ants to remove things. In their tests, filter paper treated with oleic acid was carried to the refuse piles. This “fatty acid death cue” idea was widely accepted for decades. It has since been refined. In a 2009 study of Argentine ants, researchers found that freshly killed workers were carried to refuse piles within one to two hours. The authors concluded that removal is triggered by the fading of chemical signals associated with life, not by the buildup of a death cue. Researchers continue to study how these cues work in other species.

Why do they do it?

To stop disease. Corpses carry germs. Ant researchers describe it as protecting the colony. In one experiment on the ant Myrmica rubra, colony survival suffered when workers were prevented from removing their dead, according to a later paper citing the work.

Do all insects do the same thing?

No. Different species use different methods. The Diez team notes that in most ant species corpses are removed from the nest, in some they are buried inside it, and termites bury corpses in the nest. In some ant species, sick ants leave the nest on their own before they die. In honeybees, removing the dead is a task for workers of a particular age, much like guarding the entrance, according to a recent paper from Chinese researchers. Earlier work had identified oleic acid as a death cue in the Western honeybee. But that paper found oleic acid did not trigger corpse removal in the Asian honeybee Apis cerana, and it tested a gland pheromone as another possible cue. That suggests the cues differ between species.

Is it mourning?

No evidence suggests so. This is a hygiene system run by chemical signals, and the old words “funeral” and “cemetery” are metaphors. For animals whose responses to death may involve more than chemistry, see Do Animals Understand Death?, How Primates Respond to Their Dead Infants, and Do Crows Hold Funerals for Their Dead?.

Where can I learn more?

See What Happens to a Dead Animal in Nature? and Why Do Humans Bury Their Dead?.