Managing the risks and rewards of death in eusocial insects

Abstract

Eusocial insects frequently face death of colony members as a consequence of living in large groups where the success of the colony is not dependent on the fate of the individual. Whereas death of conspecifics commonly triggers aversion in many group-living species due to risk of pathogens, eusocial insects perform cooperative corpse management. The causes and social context of the death, as well as feeding and nesting ecology of the species, influence the way that corpses are treated. The corpse itself releases cues that dictate the colony's response. As a result, social insects exhibit behavioural responses that promote disease resistance, colony defence and nutrient recycling. Corpse management represents a unique adaption that enhances colony success, and is another factor that has enabled eusocial insects to be so successful. In this review, we summarize the causes of death, the sensory detection of death and corpse management strategies of social insects. In addition, we provide insights into the evolution of behavioural response to the dead and the ecological relevance of corpse management.This article is part of the theme issue ‘Evolutionary thanatology: impacts of the dead on the living in humans and other animals’.

Death recognition by undertaker bees

“…Along the line of related researches (5), no compound of unique pheromone structure is needed for instant death recognition. Also, the CHCs signal for life in honeybees can be of same as CHCs used by solitary species in stress resistance, parasitism, aggression, competition and/or predation (34).…”

“…Also, the CHCs signal for life in honeybees can be of same as CHCs used by solitary species in stress resistance, parasitism, aggression, competition and/or predation (34). Compared with the ants and termites using specific more volatile life signal (5, 8), the body size may affect the strategies used. The climbing tiny ants and termites are less likely to be warmed up to a much higher temperature than the ambient condition, which limited the chance of using CHCs for multi-purpose.…”

“…However, what mechanisms are available to much more primitive organisms such as insects to assess whether conspecifics are alive or dead? It has been a long time, that carbonic acids derived from corpse decompose are responsible for the death recognition of dead bodies in social insects (2, 5). But this leads to theoretical and empirical conflicts.…”

“…Chemical cues specific to life or death could signal rapidly death in social insects (3, 5). For example, in ants, it has been shown that the decrease in chemical signals is correlated with death.…”

Environmental decomposition of cuticular hydrocarbons generates a volatile pheromone that guides insect social behavior

“…Fatty acids trigger different behavioral responses in different species. Some medium-chain fatty acids, like linoleic and oleic acids, act as necromones for Apis mellifera (37), P. americana (29), termites (38) and isopods (4), repelling them from sites with dead conspecifics to avoid potential risk of predation or pathogenesis. However, short- and long-chain fatty acids from feces of Blattella germanica , some of which were microbial mediated (39), elicited aggregation response (40).…”