Facultative social insects can provide insights into the reversal of the longevity/fecundity trade-off across the eusocial insects

- Facultative eusocial insects can inform on how eusociality changes lifespan.
- Hormonal pleiotropy may underpin lifespan and fecundity differences between castes.
- Transcriptome changes accompanying lifespan and fecundity differences await study.

In eusocial insects, reversal of the fecundity/longevity trade-off and extreme differences in life histories between castes of the same species garner scientific and public interest. Facultative social species at the threshold of sociality, in which individuals are socially plastic, provide an excellent opportunity to understand the causes and mechanisms underlying this reversal in life history trade-off associated with eusociality. We briefly present the ultimate factors favoring sociality and the association between fecundity and longevity in facultative eusocial insects, including kin selection and disposable soma, as well as proximate mechanisms observed in such species, such as differences in hormone titers and functions. Potential genetic underpinnings of lifespan and fecundity differences between castes are discussed and future research directions are proposed.

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