Joël MEUNIER

Living in groups is known to protect young animals from environmental dangers like predators and extreme temperatures, but its role in mitigating toxic stressors such as chemical pollution is unclear. We studied European earwig juveniles, rearing them in different social settings and exposing them to cadmium, and found that while social environment affects juvenile development and survival, it does not lessen cadmium's toxic effects. This highlights the need to explore the mechanisms behind the earwig's resistance to cadmium. This study is part of Romain Honorio's project, while he was still a postdoc (ATER) in our group.​​

In this study, we looked at whether Roundup affects the European earwig. We exposed mothers to different doses of Roundup — including doses much lower and higher than what is normally used — and observed how they cared for their eggs and young. We also looked at how Roundup affected the growth, movement, and immune defences of the juveniles. Somehow surprisingly, we found no clear effects of Roundup on the behaviour or development of either mothers or their young. This suggests that earwigs may be more resilient to this herbicide than previously thought. However, it’s still important to understand why this is the case, and whether other species show similar resilience. Overall, our research highlights the need to study a wide variety of insects to fully understand how pesticides influence ecosystems — and to help develop more sustainable farming practices. This study is part of Laura Pasquier's PhD thesis.​​

Not all species raise their young the same way—even when they look nearly identical. In this study, we uncovered key differences between two look-alike species of European earwigs (Forficula auricularia and Forficula dentata), both important in agriculture and known for their invasive success. We raised 153 females from seven populations under the same lab conditions, measuring 24 traits across their lives and focusing on how they cared for their eggs—how often they moved, protected, or inspected them. Each species followed a different strategy. F. dentata mothers delayed egg-laying to improve offspring quality but had lower hatching success. In contrast, F. auricularia mothers laid eggs earlier, increasing hatching success but producing less robust young. Most maternal behaviours were similar, though F. dentata mothers defended their eggs more strongly. These subtle differences in parenting and reproduction may help explain how both species thrive in new environments. Even among look-alikes, nature finds more than one path to success. This study is part of Laura Pasquier's PhD thesis.​​

We are thrilled to see our special issue of the journal "Insectes Sociaux" out, showcasing the amazing diversity of social lives in insects ! The aim of this special volume is to advocate for this broader definition of insect sociality by shedding light on the diverse insect taxa that exhibit social behaviours. This is achieved through a collection of nine papers that explore social behaviours across several insect orders, including Diptera, Hymenoptera, Dermaptera, Coleoptera, and Hemiptera.

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This special issue has been co-edited with my colleagues J. Quezada-Euan and Miriam Richards.

I am delighted to see our research on earwigs featured in the Knowable magazine. There's a nice overview of the fascinating biology of this insect, our recent results, and behind-the-scenes stories from me and colleagues. A very nice piece of work!

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https://knowablemagazine.org/content/article/living-world/2024/social-life-of-earwigs

We tested whether parental care mitigates the impact of cold and heat waves on eggs and juveniles in the European earwig. We exposed mothers and their eggs to three-day thermal waves of 3°C, 10°C (control), 17°C or 24°C, both 15 and 30 days after oviposition. We then measured four maternal care behaviors, maternal weight variation, as well as eggs’ developmental time, survival, and hatching rate. In the resulting juveniles, we measured weight, developmental time, thermal resistance, and the expression of six heat stress and immunity genes. We found that thermal waves reduced maternal care and induced maternal weight gain. High temperatures also decreased egg hatching success, accelerated egg and nymph development, reduced the upper thermal limit of juveniles and decreased the expression of a heat shock protein (Hsp68), while other traits remained unaffected. Overall, this study suggests that species with maternal care do not necessarily have access to effective thermal protection and may not be better adapted to climate change. This study marks the first collaboration with Irene Villalta, more results to come ...

For the environmental week in Veigné, France, I had the pleasure of giving a talk to a large general audience about the secret life of earwigs. It was such a fun and engaging experience, with many familiar faces in the crowd. I truly love sharing this kind of knowledge, and it was a wonderful evening!

We tested whether insect parental care can enhance offspring survival against infections beyond the egg-laying stage. Using European earwigs, we challenged mothers with dead bacteria and later tested the survival of both the mothers and their adult offspring after a new exposure to live bacteria. We found that mothers who were immune-challenged after laying eggs, and their offspring, had higher survival rates. However, this increased survival was due to the physical wounding of the mothers, not their exposure to the dead bacteria. The findings suggest a novel benefit of post-egg-laying parental care in insects, highlighting the role of social immunity in the evolution of family life. This study is based on the work of Manon Boucicot, a Masters student. It is also the first publication from the collaboration with the EBI laboratory in Poitiers. 

We investigated the impact of molting and maternal care on the microbiome of the European earwig. Using 16S rRNA metabarcoding to analyze the prokaryotic fraction of the core microbiome, we showed that microbiome diversity changed non-linearly during earwig development, with notable shifts occurring between developmental stages rather than during molting. Additionally, we found that maternal care influenced the microbiome of both juveniles and adults, even when the last maternal contact occurred two months prior to adulthood. These findings offer new insights into the stability of the prokaryotic microbiome in hemimetabolous insects and challenge the role of maternal care in microbiome acquisition in species with facultative maternal behavior. This study advances our understanding of microbiome dynamics in relation to developmental processes and maternal care. This is the second study of MC Cheutin's postdoctoral project funded by the ANR MicroSoc.

Many of us had the pleasure of attending the IUSSI European meeting in Lausanne this year. It was absolutely brilliant! As well as presenting our latest data on the social life of earwigs to colleagues from all over the world, we were lucky enough to meet former members of the group who now work from Finland, Germany and other French cities. It was fantastic to catch up with them and see what they've all become. It was also an incredible opportunity to meet some brilliant colleagues and think about new projects and collaborations. Hopefully some new earwig research will come out of this meeting. Well done to the organisers!