Not quite social - possible cases of gregarious behaviour of immatures of various lineages of Insecta in 100-million-year-old amber


Authors: Hörnig MK, Haug C, Müller P, Haug JT

Published in: Bulletin of Geosciences, volume 97, issue 1; pages: 69 - 87; Received 4 September 2020; Accepted in revised form 11 November 2021; Online 9 January 2022

Keywords: eusociality; sub-sociality; gregarism; fossilised behaviour; Cretaceous,

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The evolution of sociality in insects is a highly discussed topic in biology. Fossil findings are rarely included into the consideration, although they have a great potential to add also behavioural aspects to evolutionary reconstructions and can provide information about the minimum age of specific lifestyles in deep time. We briefly summarise concepts of reconstructing behaviour based on fossils and give a short overview of the concept of eusociality. The focus of this paper is the description of new findings of fossilised cases of aggregations in Cretaceous Myanmar amber. All specimens enclosed in these amber pieces are immatures. These findings come from four different lineages of Insecta: Neuroptera, Dermaptera, Orthoptera and Collembola. Some of these groups are usually not considered as typical examples for social interactions, but several grades of aggregation behaviour can be observed in all of these groups in different species living today. Active aggregation behaviour (or gregarious behaviour) can be seen as part and prerequisite of further social behaviour. Therefore, the investigation of this aspect can add new insights for a more comprehensive understanding of the evolution of complex strategies of social behaviour.


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