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Necrophoresis

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Necrophoresis is the removal of dead members of a colony from the hive or nest. The term comes from the Greek nekros, meaning corpse, and phoreo, meaning to bear constantly.

Necrophoresis is a behavior observed in the eusocial insects – certain bees, all ants, and all termites – in which workers carry the corpses of dead colony members away from the nest or hive. The removal of carcasses is essential to maintaining a sanitary environment and to keeping the remaining colony members healthy. Scientists studying necrophoretic behavior in ants note that dead colony members may be removed just minutes after death. In some social insects, this job is carried out by a special subclass of workers dubbed "undertakers." The undertakers will either haul the dead a good distance away from the nest, or in some cases will throw the carcasses on a refuse pile, which may be near the colony.

Most behaviors in social insects are guided by chemical signals or pheromones. Ants, bees, and termites use their sense of smell (or chemoreception) to sniff out threats to their colony, including sick or dead members of the community. Scientists hypothesized that dead insects must smell different than living, healthy ones, and that this is how workers are able to identify and remove deceased comrades. The working theory held that decomposing insect bodies released a new chemical signal, probably a fatty acid, which announced their death to the colony. But a recent study1 of Argentine ants showed that all ants, living or dead, actually produce these death chemicals throughout their lives. Living ants simply mask the death odor with other "life" chemicals, odors that are associated with life. Immediately upon an ant's death, these life chemicals dissipate, allowing other members of the community to detect the death odor.

Some predatory insects take advantage of this behavior by using the carcasses to lure unsuspecting workers closer. Certain termite-feeding assassin bugs, for example, will wave the remains of a dead termite just outside the entrance to the nest. When workers emerge to dispose of the carcass, the assassin bug pounces and enjoys an easy meal.

1 - How Social Insects Recognize Dead Nestmates, University of California-Riverside, May 6, 2009 (via ScienceDaily).

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