Author: Damien Gergonne

Interview with a social insect scientist: Stefano Cavallo

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Stefano is a biologist specializing in animal behavior and currently works as a research fellow in behavioral ecology at the University of Florence. In this interview, he recalls moment he realized that even ants show individual personalities. His lastest research in Insectes Sociaux can be read here.

IS: Who are you, and what do you do?

I’m Stefano Cavallo, a passionate biologist specialized in animal behaviour. I’m living in Pisa and currently work at the University of Florence as a research fellow in behavioural ecology. My interests range from communication and cognitive aspects of animal behaviour in invertebrates and beyond. At the moment, my project focuses on exploring phenotypic plasticity—particularly behavioural plasticity—in marine decapods.

IS: How did you develop an interest in your research?

Since I was a child, I’ve always been passionate about animals. Although I grew up in a city, I had the chance to keep and observe a variety of species—fish, amphibians, reptiles, birds, mammals, and of course, insects. Among them, social insects, and especially ants, have always fascinated me. Their remarkable social organization combined with apparent simplicity sparked both curiosity and deep biological admiration in me. As my studies in biology progressed, I developed a strong interest in behavioral biology. What I find most stimulating is the possibility of identifying similar behavioral patterns in evolutionarily distant species, both human and non-human.

IS: What is your favorite social insect, and why?

It’s hard to choose just one. I’m fascinated by social insects for very different reasons: for instance, the interspecific relationships of Atta ants, the communicative flight and cognitive abilities of Apis mellifera, and the complex social structure of Polistes dominula all capture my interest. What I find most stimulating is not a single species, but rather those organisms capable of challenging the “dogmas” of biology. For example, the recent discovery by Juvé et al. (2025) on Messor ibericus which destroy species definitions.

IS: What is the best moment/discovery in your research so far? What made it so memorable?

One of the best moments in my research was when I first realized that even ants—creatures we often think of as identical and mechanical—show individual personalities. That realization was unforgettable: it felt like discovering a hidden layer of complexity within a familiar world. From that moment on, I stopped seeing colonies as uniform units and started seeing them as societies of individuals.

IS: Do you teach or do outreach/science communication? How do you incorporate your research into these areas?

No, at the moment I don’t deal with these aspects but in the future I hope it can become part of my job as a scientist. I think it is important to disseminate scientific advances to a wide audience and shorten the distances between laboratories, research and the general public.

IS: What do you think are some of the important current questions in social insect research, and what is essential for future research?

As we know, the environment today is subject to strong anthropogenic pressures and global warming is shaping habitats very quickly. The effects on social insects are still poorly understood. I believe it is essential to focus on these aspects and understand how changing conditions act on the biology and behavior of social insects.

IS: Outside of science, what are your favorite activities, hobbies, or sports?

I love being in nature, trekking in the mountains, climbing, swimming and snorkelling

IS: What is the last book you read? Would you recommend it? Why or why not?

The last book I read was Entangled Life: How Fungi Make Our Worlds, Change Our Minds and Shape Our Futures by Merlin Sheldrake. I would definitely recommend it—it’s a fascinating and beautifully written synthesis of what we know about fungi. These organisms are extraordinary in the way they challenge traditional paradigms of biology and reveal how deeply interconnected life really is.

IS: How do you keep going when things get tough?

I practice tai-chi and mindfulness techniques to stay in the present moment and focus on beautiful things.

IS: If you were to go live on an uninhabited island and could only bring three things, what would you bring? Why?

I would bring a knife, a tinderbox and a book on edible plants. These three things would help me get food, be able to cook and warm up and not die of intoxication haha!

IS: Who do you think has had the most considerable influence on your science career?

I believe that the most important role was played by two high school teachers. My chemistry professor and biology professor taught me scientific rigor and wonder at the living world

IS: What advice would you give to someone hoping to be a social insect researcher in the future?

If I had to advise someone to hop to be a social insect researcher, I would tell them to follow the thirst for knowledge and not stop at appearances. I would ask him to always look with a critical eye at those who claim to have absolute certainties in biology.

IS: Has learning from a mistake ever led you to success?

I couldn’t point to a specific mistake, but I believe that in private life and at work we often learn by falling and making mistakes. Trying by trial and error: this is generally just how we manage to grow.

IS: What is your favorite place science has taken you?

My favourite place where science took me is Paris, in the experimental and comparative ethology laboratory of the Sorbonne University in northern Paris. I was lucky enough to work in the group led by Professor Patrizia d’Ettore who with dedicated passion dedicates herself to research in the myrmecological field.

Digging on fast-forward: How heat shapes ant architecture

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In this blog post, the authors of the Insectes Sociaux article title “High environmental temperatures put nest excavation by ants on fast forward: they dig the same nests, faster” (Rathery et al. 2025) talk about their research on the effects of environmental temperature on ant digging activity.

Imagine watching a video of someone doing normal everyday activities. First, at normal speed, then, at double speed: suddenly everyone moves like olympic sprinters, but still appear calm and relaxed. Now slow down the video: every step and gesture becomes painfully sluggish.

Imagine if that could also happen in real life: one day, it’s only noon and you have already wrapped up all the work for the day; the next day, you have barely had breakfast and the day is already getting to an end!

These situations look unrealistic to us, but ants experience them all the time!

Ants are ectotherms – animals that don’t maintain a constant body temperature. As a result, their physiology and behaviour depends heavily on the temperature of the environment. In warmer weather, ants move faster, they likely forage more quickly, and probably they also age faster. In our study, for instance, the walking speed of Lasius flavus ants doubled when the temperature rose by about 12 °C.

Of course, the sped-up video analogy only goes so far. For example, gravity does not change with temperature, so winged ants need to flap their wings at least at a minimum speed in order to fly, and this might become completely impossible in cold weather. At high-temperature, when ants are moving too fast, they might struggle to take in enough oxygen to keep up with their energy consumption. So, while some behaviours might simply speed up with increasing temperature, other behaviours are likely to hit a physical or physiological limit, and could change in unexpected ways. In all cases, the changes of behaviour induced by temperature are likely to be important for colony survival, and may play a role in future adaptations of ants to the changing climate.

IS: How did you choose this research topic, and to explore it with Lasius flavus?

“It was a combination of love for the topic, but also of practical circumstances”, says Alann Rathery, lead author of the study. Originally planning to study termite nests in Australia, his plans were upended by the Covid-19 pandemic. “I had to pivot quickly, soon abandoned the idea of travelling to Australia I began collecting ants from my backyard in London. At some point, I even ran some preliminary experiments in my room!“

The image is just a frame grab from the video linked: laboratory in Alann Rathery’s room where preliminary experiment leading to the present study were conducted during the Covid19 pandemic.

“Luckily, the yellow meadow ants (Lasius flavus), which are one of the most abundant ant species in the meadows of South-West London, are very interesting ants. They are important ecological engineers, that shape the local landscape with their mounds, creating ecological niches for many other plant and animal species.”

Image of a meadow disseminated with yellow meadow ant mounds. ©Wikipedia.

IS: Can you tell us a bit about the experiments that you did?

“We have long been curious about how environmental factors – like temperature and humidity – affect the behaviour of social insects” – says Andrea Perna, senior author of the study. – “These environmental cues may help ants and termites figure out things that they cannot measure directly, like how deep inside the nest they are. One of the key functions of nests is to provide the colony with a suitable environment in terms of temperature and humidity: it makes sense that insects respond to these cues. In a related study (Facchini et al. 2024), for instance we found that termites may use water evaporating from damp soil as a signal to coordinate how and where to build their nests.

When it comes to ants, previous studies had indicated that they likely respond to temperature gradients – differences in temperature across space – during nest building. But it wasn’t clear whether temperature alone, without a gradient, could influence how ants dig or build. So we set out to test two things: first, how ant digging speed changes depending on temperature, and second, whether the shape of the nests that they excavated was different at different temperatures.

We followed a somewhat classical approach for the experiments, letting ants excavate in-between two glass plates, so that we could image the growth of the pattern over time while the experimental colonies were housed inside temperature-controlled incubators”.

“The experiments were technically a bit challenging – adds Alann Rathery – we had to image ant colonies continuously over multiple days, and the space inside the incubators was a bit tight, so I had to build a custom imaging system with Raspberry Pi computers and cameras – one inside each incubator. I connected them all to a router outside, and through that I could control the cameras remotely to automatically record photos and videos.” Analyzing the footage wasn’t simple either. “The ant tunnels grow into very complex shapes, and it takes a solid analysis pipeline to automatically extract and quantify the structures. But some of the patterns they create are really beautiful!”

Do you want to see these structures grow? Here is a time-lapse video of the growing galleries.

Screen shots from the time-lapse video of the growing galleries.

IS: What’s next for this type of research?

“There’s still a lot we don’t know about what happens at the individual level when ants dig these intricate underground networks. In our study, we didn’t focus on the detailed behavior of individual ants as they carve out tunnels in the soil. But what they do, how they decide where to dig, how new branches start, are all incredibly interesting questions. Some of this behavior can be seen in action in a real-time video clip from our experiments. Analysing in detail this type of footage is fascinating, but could easily become an heavy research task.

Another promising direction for this research would be looking at the internal structure of natural nests in the wild: how do galleries inside the mound differ, depending if the mound was built in a sunlit area compared to a shady one?Are there shape differences between the northern exposed and the southern side of the mound?

The nests built by social insects are more than just shelters: they are the physical records of the life and activity of a colony. If we learn to better read the information written in these structures, we might uncover new insights into the hidden lives of these wonderful insects”.

References:

Rathery, A., Facchini, G., Halsey, L.G., Perna, A. High environmental temperatures put nest excavation by ants on fast forward: they dig the same nests, faster. Insect. Soc. (2025). https://doi.org/10.1007/s00040-025-01049-7

Facchini, G., Rathery, A., Douady, S., Sillam-Dussès, D., Perna, A. (2024). Substrate evaporation drives collective construction in termites. Elife, 12, RP86843. https://doi.org/10.7554/eLife.86843.4

Pesticides damage bee parenting — and their larvae pay the price

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By Leeah Richardson

Leeah is a graduate student at the University of Texas at Austin with a particular interest in insect behavior and anthropogenic stressors. In this blog, she explains how, although not highly lethal to adults, some pesticides can harm bumblebees in indirect ways. Her latest research on social insects can be read here.

Worldwide we use billions of pounds of pesticides each year agriculturally to control crop pests (FAO 2024) but this negatively impacts many insects that benefit crop production – for example: pollinators. Regulatory agencies do try to minimize the impact pesticides have on pollinators, but this is largely by preventing lethal effects. Pesticides don’t always have to kill bees to harm their populations and the pollination services they provide. By asking how much of a chemical is lethal to adults, we can miss subtle yet important effects on bee behavior and reproduction.

For many animals, including most bee species, offspring receive care from adults in order to survive. For example, in a bumblebee colony, worker bees chew through the wax covering their larval sisters to feed them pollen and nectar, regulate the temperature of the colony, and perform hygienic behaviors, so that these larvae can develop into adult bees. These caretaking behaviors are critical, but can be vulnerable to environmental stressors, like exposure to insecticides.

Bumblebee (Bombus impatiens) workers displaying caretaking behaviors on a brood mass.

The insecticide Flupyradifurone (FPF) is especially interesting to study in the context of how it may influence bee caretaking behaviors FPF is not likely to outright kill adult honeybees or bumblebees at the concentrations present agriculturally – so it can be sprayed on flowering crops, but recent studies have shown that it has negative effects on bumblebee larvae (Fischer et al. 2023, Richardson et al. 2024). This raises the question: are bee larvae themselves sensitive to FPF, or is the problem that exposed adults provide poorer care to developing larvae?

We conducted two experiments to determine whether FPF is directly toxic to larvae through ingestion or if FPF has indirect effects by impairing caretaking behaviors (below).

FPF could influence larvae directly (due to ingestion) or indirectly (by impairing caretaking behaviors provided by the adults).

We first did an experiment where we fed larvae by hand so that parental care was completely standardized for all of the larvae. To do this, we took larvae from an existing colony and kept each larva in an individual well of a 24-well plate, provisioning them with a sugar water/pollen mixture four times per day for three days. This mixture was either untreated (control) or contained FPF at one of four concentrations. If FPF was directly toxic, we expected to see higher mortality or delayed molting with the treated larvae. Instead, we found no differences between our untreated control groups and the treated larvae.

Process of removing all larvae from an existing colony under red light, then sorting them into size categories (instars), then placing them into individual wells in 24-well plates to be hand fed a sugar water/pollen mixture.

We then conducted a cross-fostering experiment to test for both direct and indirect effects to larvae. We created small “microcolonies” with four worker bees each that begin laying eggs and rearing offspring once separated from their queen. Half of these microcolonies were given FPF treated sugar water for two weeks, while the other half got untreated (control) sugar water.

Bumblebee microcolony with three worker bees on the brood mass they produced. Larvae are kept under the wax covering, so at the end of the experiment we peel this back to count and weigh them.

After two weeks, we swapped the adults to new microcolonies so that we now had groups of larvae that had never been exposed to FPF being cared for by FPF-treated adults, and groups of larvae that had been exposed to FPF being cared for by untreated (control) adults for three days (see figure below). This design allowed us to see whether larval outcomes depended on what the larvae themselves had previously ingested or on the status of their caretakers.

Design of our cross-fostering experiment to decouple adult and larvae exposure during the second phase and we found that whether the adults had been treated during phase 1 most influenced the size of the larvae we recovered from the microcolonies (adapted from Richardson et al. 2025).

We expected that if FPF directly impaired the larvae then whether or not the larvae themselves had been exposed to FPF for the two weeks prior to cross-fostering would strongly influence larval outcomes, but if indirect effects due to impaired parental care was most important then whether or not the adult caretakers had been exposed to FPF would instead be most influential. We found that it was the adult exposure to FPF that had the largest impact on larval outcomes (particularly the size of the larvae). Larvae tended by FPF-exposed adults were consistently smaller than those cared for by untreated adults, regardless of whether the larvae themselves had ingested FPF previously.

Both our hand-feeding and cross-fostering experiments showed that the larvae were surprisingly tolerant to direct FPF exposure via ingestion, but they were highly sensitive to impaired care. Together, these findings suggest that FPF’s harm to bumblebee larvae is driven mainly by changes in adult behavior, not by direct toxicity to the young.

Bee declines are complex, driven by habitat loss, climate change, disease, and pesticides (Goulson et al. 2015). Our study highlights the importance of testing not just whether pesticides kill adults, but also whether they disrupt the social and parental behaviors that larvae depend on. Future work should extend these kinds of experiments across more bee species and under field conditions, where multiple stressors interact.

References:

Fischer, L. R., Ramesh, D., & Weidenmüller, A. (2023). Sub-lethal but potentially devastating—The novel insecticide flupyradifurone impairs collective brood care in bumblebees. Science of The Total Environment, 903, 166097. https://doi.org/10.1016/j.scitotenv.2023.166097


Goulson, D., Nicholls, E., Botías, C., & Rotheray, E. L. (2015). Bee declines driven by combined stress from parasites, pesticides, and lack of flowers. Science, 347(6229), 1255957. https://doi.org/10.1126/science.1255957


Pesticides use and trade. 1990–2022. (2024). Food and Agricultural Organiation of the United Nations. https://www.fao.org/statistics/highlights-archive/highlights-detail/pesticides-use-and-trade-1990-2022/en


Richardson, L. I., DeVore, J., Siviter, H., Jha, S., & Muth, F. (2025). Bumblebees exposed to a novel ‘bee-safe’ insecticide have impaired alloparental care and reproductive output. Insectes Sociaux. https://doi.org/10.1007/s00040-025-01054-w


Richardson, L. I., Siviter, H., Jha, S., & Muth, F. (2024). Field‐realistic exposure to the novel insecticide flupyradifurone reduces reproductive output in a bumblebee (Bombus impatiens). Journal of Applied Ecology, 61(8), 1932–1943. https://doi.org/10.1111/1365-2664.14706

Insect architects: How termites, ants, and bees build without blueprints

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by Paige Caine

Paige Caine is a PhD student in Dr. Michael Goodisman’s lab at Georgia Tech. She study fire ants and yellowjackets wasps. In this blog, she explains how social insects, such as termites, ants, or bees, collectively manage to build complex nests. Her latest research on social insects can be read here.

A builder stands at the foot of her construction, a massive skyscraper towering thousands of times her height. The imposing architectural feat stretches stories underground as well, and is home to thousands of individuals. She can’t see the results of all her hard work though; she’s blind. In fact, the entire team of builders responsible for the structural triumph is blind, and they didn’t have a chief architect or any blueprints to guide them. How did they do it?

To answer this question, let’s meet the construction crew: Cathedral Termites. Native to Australia, this species of termites has blind workers measuring only about 3-4.5 millimeters long, yet they build massive nests to house their queens, kings, and young. 

A Cathedral Termite (Nasutitermes triodiae) mound.

But this feat isn’t unique to Cathedral Termites—most social insects construct some form of nest. These structural marvels range in size and shape, from Cathedral Termite mounds to charismatic honeybee hives to tiny ant homes contained within acorns.  In the absence of realtors, social insects often use collective decision-making to choose a nest location that optimizes temperature, sunlight, precipitation level, predation risk, and proximity to resources (Jeanne and Morgan 1992; London and Jeanne 2000; Suzuki et al. 2007). These strategies typically involve sending a few scouts to locate potential nesting sites. The scouts then recruit colony-mates to “vote” on sites by physically going to that site and contributing to the recruitment effort. Eventually, a quorum is reached, and the losing party packs up from their rejected sites and heads to the winning location (Pratt 2005).

Once the site has been chosen, a range of different construction methods are used to build the nest. Termites and ants tend to excavate their homes, while social bees and wasps tend to build their homes from manipulated biological material—chewed up wood pulp in the case of social wasps or wax in the case of some bees.

A social wasp nest from the yellowjacket Vespula squamosa. While these structures are built underground, this nest has been excavated (left), and then separated into the individual layers of comb (right).

A common problem during collective construction—and one most human commuters are accustomed to—is crowding. To excavate a massive structure composed of tunnels and chambers, ants and termites must navigate narrow spaces containing hundreds or even thousands of individuals. One way termites solve this problem is through something referred to as a “bucket brigade;” like humans passing water towards a fire via a series of buckets, some termite species form a queue and pass excavated material along from individual to individual until it reaches the deposition site (Bardunias and Su 2010). Some ants, on the other hand, utilize “laziness” to avoid crowding, by having certain individuals sit still while a minority actually contributes significantly to construction (Aguilar et al. 2018).

But, if there’s no blueprint and no architect in charge of doling out specific tasks, how are all these individual construction behaviors coordinated?

One common means of coordination is stigmergy, which means communicating across time via the environment. Each time an individual interacts with the incipient construction, they leave behind traces of their behavior, either by shaping the material or leaving behind chemicals. These cues tell individuals who later approach the construction what has been done, and what’s left to do.

A diagram displaying stigmergy at work in honeybee nest construction, based on (Nazzi 2016). Different colored bees indicate distinct individuals A) Bee #1 interacts with cells constructed by her nestmates. B) Cells act as cues for bee #1 to extend the floor of the nest. C) Floor acts as a cue for bee #2 to begin constructing stubs of a wall. D) Third bee detects these wall stubs and responds by adding to the stubs to encircle a cell. E) Fourth bee notices cells constructed by her nestmates and responds by extending the floor further. F) After additional building activity by several bees, the comb of cells hits the edge of the cavity.

Now that we know how social insects build their remarkable nests, another natural question is why?

Social insect nests offer many advantages to residents. For one, they offer protection from weather, much like a human home. They also protect against infection, with many species actively incorporating antimicrobial bacteria or other antibiotic agents into the walls (Tranter et al. 2013; Madden et al. 2013; Chouvenc et al. 2013). Nests also enable protection against larger threats, functioning as defendable fortresses. In fact, many species employ guards at nest entrances, and often close their doors at night (Bennett and Baudier 2021).  Finally, nests help large insect societies organize their behaviors by physically contributing to division of labor, as well as by influencing the efficiency of collective tasks like foraging.

Termites nesting in paper (left), which they eat as they construct. Ants nesting in soil (right), showcasing some of the many interior tunnels and chambers.

Overall, social insect nest construction is an impressive feat, and the results are both structurally remarkable and highly functional. One day, we may be able to imitate such techniques using swarm robotics. Today, many engineers are already working on bio-inspired robot collectives capable of construction. Robotic models are even being designed to test hypotheses about collective behaviors in social insect groups, an approach recently termed “robophysics.” In the future, robophysical models may unlock some of the principles underlying social insect nest construction, strengthening our understanding of collective behavior in both engineering and biology.

Robots engaged in construction. Left photo credit: Eliza Grinnell/Harvard SEAS. Right photo credit: Daniel Soto, Joonha Hwang

References:

Aguilar J, Monaenkova D, Linevich V, et al (2018) Collective clog control: Optimizing traffic flow in confined biological and robophysical excavation. Science 361:672–677. https://doi.org/10.1126/science.aan3891

Bardunias PM, Su NY (2010) Queue Size Determines the Width of Tunnels in the Formosan Subterranean Termite (Isoptera: Rhinotermitidae). J Insect Behav 23:189–204. https://doi.org/10.1007/s10905-010-9206-z

Bennett MM, Baudier KM (2021) The Night Shift: Nest Closure and Guarding Behaviors in the Stingless Bee, Tetragonisca angustula. J Insect Behav 34:162–172. https://doi.org/10.1007/s10905-021-09779-9

Caine, P.B., Robertson, A.T., Treers, L.K. et al. Architecture of the insect society: comparative analysis of collective construction and social function of nests. Insect. Soc. (2025). https://doi.org/10.1007/s00040-025-01057-7

Chouvenc T, Efstathion CA, Elliott ML, Su N-Y (2013) Extended disease resistance emerging from the faecal nest of a subterranean termite. Proceedings of the Royal Society B: Biological Sciences 280:20131885. https://doi.org/10.1098/rspb.2013.1885

Jeanne RL, Morgan RC (1992) The influence of temperature on nest site choice and reproductive strategy in a temperate zone Polistes wasp. Ecological Entomology 17:135–141. https://doi.org/10.1111/j.1365-2311.1992.tb01170.x

London KB, Jeanne RL (2000) The interaction between mode of colony founding, nest architecture and ant defense in polistine wasps. Ethology Ecology & Evolution https://doi.org/10.1080/03949370.2000.9728440

Madden AA, Grassetti A, Soriano J-AN, Starks PT (2013) Actinomycetes with Antimicrobial Activity Isolated from Paper Wasp (Hymenoptera: Vespidae: Polistinae) Nests. Environ Entomol 42:703–710. https://doi.org/10.1603/EN12159

Nazzi F (2016) The hexagonal shape of the honeycomb cells depends on the construction behavior of bees. Sci Rep 6:28341. https://doi.org/10.1038/srep28341

Pratt SC (2005) Quorum sensing by encounter rates in the ant Temnothorax albipennis. Behav Ecol 16:488–496. https://doi.org/10.1093/beheco/ari020

Suzuki Y, Kawaguchi LG, Toquenaga Y (2007) Estimating nest locations of bumblebee Bombus ardens from flower quality and distribution. Ecol Res 22:220–227. https://doi.org/10.1007/s11284-006-0010-3

Tranter C, Graystock P, Shaw C, et al (2013) Sanitizing the fortress: protection of ant brood and nest material by worker antibiotics | Behavioral Ecology and Sociobiology. Behavioral Ecology and Sociobiology 68:499–507. https://doi.org/10.1007/s00265-013-1664-9

At what point does a male social wasp leave his natal nest to reproduce?

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By Daniela Torres Garcia

In this blog, Daniela Torres Garcia, from the University of São Paulo, describe how she discovered that the number of females in a Mischocyttarus cerberus wasp nest influences the departure of males for mating. This latest research on social insects can be read here.

In social hymenopterans, male reproductive success depends entirely on the timing of reproduction, as males play no role in maintaining the colony—at least in the widely studied species. Males of many species, including social wasps, undergo post-pupal sexual maturation within the natal nest before dispersing to mate, during which time they rely on their nestmates for protection and food.

This leads us to a key question: do all males leave the nest at the same time, or is there something that makes some of them stay longer or shorter in their natal nest?

To answer this, we observed a population in southeastern Brazil of the Neotropical species Mischocyttarus cerberus. We conducted a rigorous monitoring of the nests of this species over several weeks to track male dispersal, and we found that the time a male spends in the nest before leaving varies. Some males leave the day after emerging, while others remain for almost a week.

Nest of M. cerberus with females and males. Photo by Andres Rodrigues De Souza.

Given this variability, we asked what factors might be influencing male dispersal timing. Does the social context affect this variability? That is, does the number of adult females in the nest influence how long the males stay? Do males stay longer when more adult females are present?

We addressed these questions using two approaches: on the one hand, observationally, by monitoring 36 natural nests; on the other hand, experimentally, by manipulating the number of females in 22 nests to see whether this caused a change in male dispersal behavior. And what did we find? Males in nests with more females stayed longer, thereby delaying their dispersal.

On average, males left after 3 days, but some took up to 8 days. We found that in nests with three females, males stayed for about 2.8 days, whereas in nests with only one female, they left after just 1.7 days. This suggests that females modulate male dispersal, which can last up to 8 days—similar to another social wasp, Polistes lanio (up to 7 days) (Southon et al., 2020). Why? Probably because staying in the nest is safer and more comfortable. More females mean better defense against predators and more food available. It is worth remembering that the sting—the primary defense mechanism of this group—is associated with the female reproductive system and thus is absent in males.

Male M. cerberus resting on the underside of a leaf within the study area. Photo by Andres Rodrigues De Souza.

Therefore, it is not surprising that males from nests with more females delay their dispersal to complete their sexual maturation in a safer and more comfortable environment, thereby increasing their survival and future reproductive competitiveness (i.e., by accumulating energy reserves). The accumulation of these reserves could help them avoid having to expose themselves on flowers to obtain food once dispersed.

Taken together, these results highlight the role of social context in shaping male reproductive strategies and suggest that pre-dispersal social life may be an underestimated factor in the physical fitness of males in social insects.

The reproductive biology of male social insects has often been studied at mating sites, such as leks and swarms (Beani et al., 1992; Beani et al., 2014). However, less attention has been given to male behavior prior to reaching these sites (e.g., Southon et al., 2020), despite its potential to influence male competitive ability. Therefore, pre-dispersal social life may be an overlooked aspect of male paper wasps’ reproductive strategies.

Left: Researcher tagging M. cerberus males for tracking, under an air conditioning unit. Right: M. cerberus nest under study, with several workers visible on the cells

References

Beani L, Dessì-Fulgheri F, Cappa F, Toth A (2014) The trap of sex in social insects: from the female to the male perspective. Neurosci Biobehav Rev 46:519–533. https://doi.org/10.1016/j.neubiorev.2014.09.014

Beani L, Cervo R, Lorenzi CM, Turillazzi S (1992) Landmark-based mating systems in four Polistes species (Hymenoptera: Vespidae). J Kansas Entomol Soc 8:211–217 https://www.jstor.org/stable/25085358

Garcia, D. T., Santos, E. F., Santos, S. A., do Nascimento, F. S., Krams, I., Rantala, M. J., & de Souza, A. R. (2025). Social context predicts male dispersal in nests of a paper wasp. Insectes Sociaux, 1-4. https://doi.org/10.1007/s00040-025-01050-0

Southon, R. J., Radford, A. N., & Sumner, S. (2020). Hormone-mediated dispersal and sexual maturation in males of the social paper wasp Polistes lanio. Journal of Experimental Biology, 223(23), jeb226472.

Sunning clusters, the remarkable phenomenon in red wood ants: What causes their occurrence?

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By Peter Chanas

Peter recently completed his Ph.D. at Charles University in Prague. During his doctoral study, he focused on the formation of sunning clusters, the phenomenon in red wood ants as a part of their nest thermoregulation. Currently, he is looking for a research position on ants. Read his latest article in Insectes Sociaux here.

While walking in the European coniferous forest during early spring, some large hills are covered by needles; these are the anthills. If you get closer and look at one of them closely, you will notice a black spot on the nest surface. These are red wood ants, Formica polyctena. They often form huge and dense clusters on the nest surface, in which many ant workers (even queens!) are involved throughout the whole spring.

A close-up view of densely overlapping ant workers of Formica polyctena forming a sunning cluster. How many ant queens can you find here? © Peter Chanas

You may be asking intuitively: Why are they doing this on the nest surface? A long time ago, Zahn (1958) suggested that when ants return to their nest after sun basking, they could transfer heat and thus contribute to the increase in nest temperature. It has been confirmed that sun-basking behavior contributes to the spring nest heating (Chanas and Frouz 2025b). Although the effect on the nest temperature is low, there are other factors which can contribute to the spring nest heating within overall nest thermoregulation. And that is what our research questions were: What factors cause the ants to form clusters on the nest surface? How often do clusters occur?

Sunning clusters, the remarkable phenomenon, occurred in all nests we studied. We were surprised that there was no significant relationship between the occurrence of sunning clusters and nest volume and nest shading, even though such nest properties were shown as crucial in ant nest thermoregulation (see references in our article). Our results suggest that there is a high variation of workers performing sun-basking behavior among individual nests, as similarly shown by Kadochová et al. (2017). It also means that each nest has slightly different microclimatic conditions. Each nest inhabits many ant individuals, which can behave according to it and then ensure optimal temperature conditions in the given nest.

  • Why do we call clusters “sunning?” Because when the sun shines, ants form clusters on the nest surface, and the main heat source is the sun, so they form “sunning clusters.” This is their distinctive and conspicuous behavior, and it has attracted the attention of several scientists interested in ant nest thermoregulation.

The frequency of clusters strongly depends on the nest temperature and the duration of daylight, unlike the air temperature, which has a lower effect. Thus, at lower nest temperature, ant workers tend to form sunning clusters during warm periods of the day, with a higher outside temperature. At higher nest temperature, clusters are formed during the cold period of the day. We found that the breaking point of the nest temperature where clusters peaked was 4.68°C and of the daylight was 12 h and 40 min. After that, sunning clusters declined very slowly, which you can see only by the statistics. The low nest temperature is very interesting; we expected a different breaking point of nest temperature. Why such a low nest temperature? But sun-basking behavior is just one of several mechanisms within nest thermoregulation. The fact that you do not know something is even more interesting because you can still further ask, think, and feed your curiosity by trying and setting up new experiments and expanding knowledge and contributing to the science and then the whole society to moving on.

Sunning clusters did not completely disappear at the nest temperature above 20ºC, where the opposite was shown by Kadochová et al. (2019). There was rather a gradual decline of clusters. Higher nest temperature accelerates reproduction and is crucial for their proper brood development (Rosengren et al. 1987, Porter 1988). At such high nest temperature, they do not need to further form sunning clusters. Although some workers can still perform sun-basking behavior by their individual need.

If you look at the daily dynamic of occurrence of clusters, you can see that the pattern is different in early spring and different in late spring. Thus, the daily dynamic changed significantly in early and late spring (Fig. 2). In early spring, when the nest temperature is low, sunning clusters peaked in late morning and then decreased. In late spring, however, we found that once a nest heated up, the clusters became much less frequent and occurred without a clear diurnal pattern but in obvious association with colder weather.

Based on Chanas and Frouz 2025.

We had a huge dataset. A large dataset was generated, including nineteen cameras (Fig. 3). By using the cameras, we were able to notice something that the ordinary eye would not notice in the field. When you have “more eyes” looking at something, you are more likely to notice things you had not considered—because the mind tends to only see what it is prepared to see. In this case, we noticed clusters in association with colder weather that occurred sometime even in late spring. Such clusters we called “non-sunning clusters” (Fig. 4). This was a surprising finding, prompting the question: Why do they occur there under a cloudy sky or in cold weather for most of the day in early spring—and sometimes even during brief periods in late spring? These clusters likely have no significant effect on the regulation of nest temperature. But it can bring new insight into the organisation of ant colonies, but it needs further investigation. Currently, we are working on further findings based on another dataset that will expand our knowledge of ant nest thermoregulation.

One scouting camera from nineteen cameras installed on a tree used to record the occurrence of sunning clusters on the nest surface during spring. Peter would like to thank the field assistants: Jaroslav Kukla, Veronika Jílková and Štěpánka Kadochová, for their help with the installation of scouting cameras on trees. © Peter Chanas
Example of “non-sunning clusters” recorded by the scouting camera. Such clusters only occasionally occurred during the day in early spring. © Peter Chanas

Since ants are ectothermic animals, the formation of clusters can be quite “mechanical”. Due to their reaction to change the nest temperature and environmental conditions. A simple and plausible algorithm for cluster formation could be based on environmental conditions and social cues: in cold weather and in the presence of other workers on the nest surface, individuals tend to cluster together. When the nest surface is cold, they seek sunlight when available; when it becomes hot, they move into shaded areas to avoid overheating (Kadochová et al. 2019). Similar to how people enjoy basking in the sun during early spring but more avoid it during the peak of summer, red wood ants adjust their behavior based on nest and air temperature. However, unlike humans, they form clusters—an adaptive strategy that reduces their surface-to-volume ratio, helping to minimize heat loss compared to individual ant workers.

In conclusion, red wood ants tend to form clusters on the nest surface in early spring when nest temperatures are low or when workers are exposed to cold conditions. This behavior likely persists into late spring during chilly mornings, evenings, or periods of cold weather. In essence, the formation of sunning clusters is closely tied to nest temperature, air temperature, and daylight availability. Red wood ants appear to integrate cues from both inside the nest (internal temperature) and the external environment (sunlight or cold) to decide whether or not to form sunning clusters on the nest surface.

References

Chanas P., Frouz J. 2025b. Sunning clusters of ants contribute significantly, but weakly to spring heating in the nests of the red wood ants, Formica polyctena. Eur. J. Environ. Sci. 15: 28–33. https://doi.org/10.14712/23361964.2025.4

Kadochová Š., Frouz J., Roces F. 2017. Sun basking in red wood ants Formica polyctena (Hymenoptera, Formicidae): Individual behaviour and temperature-dependent respiration rates. PLoS ONE 12(1): e0170570. https://doi.org/10.1371/journal.pone.0170570

Kadochová Š., Frouz J., Tószögyová A. 2019. Factors influencing sun basking in red wood ants (Formica polyctena): a field experiment on clustering and phototaxis. J. Insect Behav. 32: 164–179. https://doi.org/10.1007/s10905-019-09713-0

Rosengren R., Fortelius W., Lindström K., Luther A. 1987. Phenology and causation of nest heating and thermoregulation in red wood ants of the Formica rufa group studied in coniferous forest habitats in southern Finland. Ann. Zool. Fennici 24: 147–155.

Porter S.D. 1988. Impact of temperature on colony growth and developmental rates of the ant, Solenopsis invicta. Journal of Insect Physiology 34: 1127–1133. https://doi.org10.1016/0022-1910(88)90215-6

Zahn M. 1958. Temperatursinn, Wärmehaushalt und Bauweise der Roten Waldameisen (Formica rufa L.). Zoologische Beiträge 3: 127–194.

What makes a queen successful?

/ Damien Gergonne / Leave a comment

By Luisa M. Jaimes-Nino

Luisa is a researcher at Johannes Gutenberg University Mainz. She specializes in studying the life-history traits of ants, their senescence, and the genetic and non-genetic mechanisms influencing queen fitness. Read her latest article in Insectes Sociaux here.

Queens, and kings in termites, are highly fertile and long lived insects. But certainly there is variation to which extent they are fertile. We were intrigued to understand what causes variation in fitness traits?

A Cardiocondyla obscurior queen (right), and brood and workers (left). ©Laure-Anne Poissonier.

We wondered if very fertile queens were also more successful by producing very fertile daughters. Is this caused by a genetic factor or perhaps the maternal status, such as maternal age? Old mothers might produce less fit queens and workers, and this can have a detrimental effect for the future of the whole colony. The negative effect of parental age, known as Lansing effect, has been documented across a wide range of taxa but not yet investigated in social insects.

We used Cardiocondyla obscurior ants as model given their high variability in fertility and  longevity. We investigated how fertility varies by selecting mothers that produced a low and high number of eggs after 15 weeks. We profited from a study in which we monitored a batch of queens in controlled conditions for their entire life (Jaimes-Nino et al., 2022), and monitored their daugthers too, to test if they presented a similar fertility and longevity.

In this experimental study, each daughter queen was mated to her wingless brother, kept in a single-queen colony on a plaster nest, and monitored monthly for productivity (i.e., number of eggs and pupae produced). ©LM Jaimes-Nino.

Our model species is polygynous, meaning that a large number of queens cohabit within a single colony. However, it is known that those queens that live longer, produce also more eggs (Kramer et al., 2015) and more queen daugthers (Jaimes-Nino et al., 2022). Previous studies have shown that queens remain heathly for a long portion of their lives because their mortality rate and gene expression pattern remain stable until old age (Harrison et al., 2021; Jaimes-Nino et al., 2022). Therefore, it is important to test whether old queens produce daugthers that are equally fit compared to those of younger queens, given that they produce the majority of them within the colony!

A) Wingless male and queen, B) three chambered plexiglas insert covered by plastic foil served as nest, and C) queen (right) and (worker) with brood inside the artificial nest chamber. ©Photo LM Jaimes-Nino.

Our results showed that mothers and daugthers do not “look” alike —  they do not have a similar fertility or longevity. This could indicate that their genetic background does not account for the observed variation. This can be expected from C. obscurior, as it exhibits extreme inbreeding.

Furthermore, contrary to the Lansing effect reported in other taxa, we found that daugthers produced by old mothers were just as fit as those produced by young mothers. This aligns with the hypothesis that, since the majority of sexuals are produced later in life, there must be mechanisms in place to maintain the health of these queens as they age! We believe that selection against aging remains strong in older queens. The specific mechanisms by which C. obscurior queens are able to produce equally fit daugthers at such advanced ages awaits further investigation.

Wingless (ergatoid) males with long mandibles mate in the nest with closely related gynes. ©Laure-Anne Poissonier.

Strikingly, the maternal lines differed in productivity suggesting background variation influenced by the maternal environment or male quality. In this species, ergatoid males (worker-like males) figth against rivals to monopolize queen access. Our study offers new avenues of research, to disentangle the effect of mother, father and developmental environment, on the final reproductive success of queens.

References

Harrison, M.C., Jaimes Niño, L.M., Rodrigues, M.A., Ryll, J., Flatt, T., Oettler, J., et al. 2021. Gene Coexpression Network reveals highly conserved, well-regulated anti-ageing mechanisms in old ant queens. Genome Biology and Evolution 13: 1–13. https://doi.org/10.1093/gbe/evab093

Jaimes-Nino, L.M., Heinze, J. & Oettler, J. 2022. Late-life fitness gains and reproductive death in Cardiocondyla obscurior ants. eLife 11: 1–17. https://doi.org/10.7554/eLife.74695

Kramer, B.H., Schrempf, A., Scheuerlein, A. & Heinze, J. 2015. Ant colonies do not trade-off reproduction against maintenance. PLoS ONE 10: 1–13. https://doi.org/10.1371/journal.pone.0137969

What does a stingless bee eat?

/ Damien Gergonne / Leave a comment

By Elyrice Alim

Elyrice, a researcher specialising in stingless bees in Malaysia, shares her observations on their diet, their favourite plants and the secrets of their unique honey. Read her latest article in Insectes Sociaux here.

During one of my honey sampling trips, I noticed that the farm does not keep the Antigonon leptopus plant. It is strange, because I was informed this is a popular stingless bee food plant and I have not seen one without any insects on a good weather. Locally called air mata pengantin (bride’s tears), I have seen this plant everywhere because it is a beautiful creeper with pink flowers. It brings vibrant colours to fences and even planted in oil palm plantations to attract insects away from the prized commodity. It is not difficult to maintain, so why not? I posed the question to the kind beekeeper, and the answer was simple: “ I did, but the stingless bees did not seem to be attracted to them so I got rid of the plant to make space for my crops”.

Stingless bee on Antigonon leptopus plant © Elyrice Alim

Stingless bees forage plants for food in the form of nectar (carbohydrate source), and pollen (protein source).  Between these two, nectar- which is later transformed into honey, is more important as this is the energy source while pollen is more crucial for breeding.

In Malaysia where I live, local stingless bee honey is at least three times more expensive than honey from honey bees. This is mostly due to the limited volume of production. Despite its lower productivity, meliponiculture or stingless beekeeping has its advantage here because it does not sting, it is native, and there is a common belief that it offers more therapeutical benefits than other type of honeys. This belief is not just a marketing strategy. There is a recent finding that proves an abundance of trehalulose in the stingless bee honey (Fletcher et al., 2020), which is lower in glycaemic index. Although there is few studies linking the plant sources to honey quality, past research from the Neotropics have shown that the therapeutic quality of stingless bee honey is indeed influenced by the botanical origin of the nectar, as well the species of stingless bees producing them (Camou-Guerrero et al., 2020).

What first piqued my interest on stingless bees was the honey, which is very distinct from honey bees’ honey. It is sour, watery and after taking into consideration the cost, it is not my first choice of spread over a breakfast toast. I was told this distinct taste is owed to the stingless bees’ smaller size, enabling them to reach special reserve of nectar where the bigger bees could not. If this is true, which plant could it be?

I started compiling a list of bee plants two years ago as a reference to start my master’s research on stingless bee plant preference. I quickly became aware that stingless bees are considered polylectic, or generalist when it comes to plant preference, much like the honey bees. Perhaps I was a bit disappointed on this, as I expect to discover something…more unique. Bee plant list from books and open sources inclined towards honey bee forage. Useful reference for stingless bees usually came from the Neotropics. Upon further searches, I found that most studies on stingless bee plant foraging in the Southeast Asian countries are site-specific. I thought, I could really use a compiled dataset, but no one seems to have done this specifically for this region. This has led to our latest article- A Review of Stingless Bee Plant Sources in the Indo-Malayan Region.

A typical setup of small-scale stingless bee farm taken at Sepanggar, Kota Kinabalu, Sabah. The area needs to be kept clean from rotten materials, kept cool (under shade or insulating material) and the entrance must not be facing another hive box entrance. © Elyrice Alim

In this review, we compiled stingless bee plant list from twenty-six studies in the Indo Malayan region. In terms of bee species, researchers seemed to incline towards the commercial stingless bee species, for example, the species of choice in Malaysia is Heterotrigona itama. We noticed that the top two plant families, Fabaceae and Asteraceae correspond to findings from other eco-regions (Bueno et al., 2023) but the subsequent or ‘secondary’ plant families of choice are different. We also did not expect Orchidaceae, the second most- specious plant family in this region to be less prominent. It is interesting to find that the most popular plant species does not come from the Fabaceae or Asteraceae family (clue: the flowers are clustered, which saves the stingless bees’ energy).

Stingless bees (Heterotrigona itama) at the entrance of a box hive. © Elyrice Alim

The result of our review reminds one to be prepared for the unpredictable nature of- well, the natural environment. For instance, the Antigonon leptopus did not appear in our top ten plant species list. Perhaps, many beekeepers, like the one I encountered, observed the same situation. It is more than probable that a polylectic bee can still be choosy when there are choices.

References

Alim, E., Yek, S.H. A review of stingless bee plant sources in the Indo-Malayan region. Insectes Sociaux (2025). https://doi.org/10.1007/s00040-025-01033-1

Bueno, F. G. B., Kendall, L., Alves, D. A., Tamara, M. L., Heard, T., Latty, T., & Gloag, R. (2023). Stingless bee floral visitation in the global tropics and subtropics. Global Ecology and Conservation, 43, e02454. https://doi.org/10.1016/j.gecco.2023.e02454

Camou-Guerrero, A., Reyes-González, A., Reyes Salas, O., Ramírez-Arriaga, E., Vicente Vega Peña, E., Martínez, J., Lucero Romero-Martínez, D., & Lilia Torres-Juárez, A. (2020). Pot-Pollen and Pot-Honey from Stingless Bees of the Alto Balsas, Michoacán, Mexico: Botanical and Physicochemical Characteristics. In V. De Alencar Arnaut De Toledo & E. Dechechi Chambó (Eds.), Honey Analysis—New Advances and Challenges. IntechOpen. https://doi.org/10.5772/intechopen.86927

Fletcher, M. T., Hungerford, N. L., Webber, D., Carpinelli de Jesus, M., Zhang, J., Stone, I. S. J., Blanchfield, J. T., & Zawawi, N. (2020). Stingless bee honey, a novel source of trehalulose: A biologically active disaccharide with health benefits. Scientific Reports, 10(1), 12128. https://doi.org/10.1038/s41598-020-68940-0

Ant engineers: how team transport inspires tomorrow’s robotics

/ Damien Gergonne / Leave a comment

By Carmen Gil-Hoed

In this blog, Carmen, a biology student at the Autonomous University of Madrid, describes how ants team up to carry food that’s too big for one ant alone. She reveals how they coordinate their efforts—and sometimes struggle—to get the job done. Their teamwork is so impressive it even inspires robotics research! Read her latest article in Insectes Sociaux here.

While foraging, ants often encounter food items too large for a single worker to carry. To overcome this challenge and optimize food intake by the colony, some species have evolved cooperative transport, a behaviour in which multiple individuals work together to move an object that is too large for a single ant to carry. Aside from humans, ants are the only animals known to regularly engage in large-scale cooperative transport (Czaczkes & Ratnieks, 2013).

The study species, Anoplolepies gracilipes. ©Sarnat (2008)

Why not all ant species engage in cooperative transport? And why do we see such a wide range of abilities? From species where the transported objects seem to fly directly to their goal, to others where there is no coordination and movement is slow and inefficient. By describing the well-coordinated cooperative transport in the invasive ant Anoplolepies gracilipes, we hope our work brings us closer to answering these questions soon.

We studied whether A. gracilipes ants visit a foraging area with Diacamma rugosum footprints and how the presence of these footprints affected their decision to cooperatively transport food by using a Y-maze. We tested three experiments: D. rugosum footprints Vs. nest matesfootprints, D. rugosum footprints Vs. No footprints and nest mates footprints Vs. No footprints. During the test runs we recorded the retrieval time for each item, its weight, the number of ants involved in transport and their positions.

The experimental set-up. Three arm combinations were tested using a Y-maze. ©Carmen Gil.
Here is an example of Crazy Yellow Ant engaging in the cooperative transport of a 0,11g cockroach. ©Carmen Gil.

96 times out of 144 (66.7%) the cockroaches were successfully transported to the nest through a tight (3 cm) paper branch. This indicates a high level of coordination among the ants. When the ants failed, they mostly did it by falling out of the paper branch. This shows that while the ants seem strong enough to carry the load, navigation errors can occur. Suggesting that the biggest challenge during the transport is the coordination of forces.

One thing we observed was that the number of workers involved in cooperative transport increased with the load’s weight. This pattern is consistent with findings in other ant species like: Eciton burchellii and Dorylus wilverthi (Franks et al., 2001). It demonstrates that ants can assess transport difficulty and determine the necessary number of individuals for the task. However, the underlying mechanism behind this decision-making process remains unclear and needs further investigation. Another interesting finding is that the probability of successfully carrying an item to the nest increased with the number of ants involved in the transport and decreased with the weight of the prey item. Further, we observed that while A. gracilipes ants adjusted the number of carriers during transport, they appeared to reach a saturation point beyond which no additional ants joined. These results suggest that having more workers in the transport group than necessary may lead to wasted effort (McCreery and Breed, 2014).

The cooperative transport in Anoplolepis gracilipes. The number of ants engaged in cooperative transport increased with the weight of the transported item.

Cooperative transport is an intriguing behaviour as it requires coordination of movements and efforts among multiple individuals. Further research should investigate the mechanisms underlying the stability of transport groups, focusing on the rules that determine when ants join or leave and how they overcome navigation failures. Cooperative transport has multiple applications such as in the field of robotics. A recent trend in Artificial Intelligence and Operations Research takes inspiration from social insects, using them as a model for developing problem-solving techniques and optimization algorithms. This same idea fuels swarm-based or collective robotics. Researchers design distributed control systems that let groups of robots work together efficiently, taking as an example the cooperative transport done by ants (paper de robotics) so robots can reach a form of decentralized decision-making.

References:

Czaczkes T, Ratnieks F. 2013. Cooperative Transport in Ants (Hymenoptera: Formicidae) and elsewhere. Myrmecological News 18:1–11.

Kube, C. R., & Bonabeau, E. 2000. Cooperative transport by ants and robots. Robotics and Autonomous Systems, 30: 85–101. doi:10.1016/S0921-8890(99)00066-4

McCreery HF, Breed MD. 2014. Cooperative transport in ants: a review of proximate mechanisms. Insect Soc 61:99–110. doi:10.1007/s00040-013-0333-3

Franks NR, Sendova-Franks AB, Anderson C. 2001. Division of labour within teams of New World and Old World army ants. Animal Behaviour 62:635–642. doi:10.1006/anbe.2001.1794

How does a caterpillar use its tentacles to get the attention of ants?

/ Damien Gergonne / Leave a comment

By Amalia Ceballos-González

In this blog, Amalia from the University of São Paulo tells the story of how she and her colleagues studied a strange functional behaviour in a myrmecophilous riodinid caterpillar. Read her latest article in Insectes Sociaux here.

Caterpillars that establish close interactions with ants have developed various adaptations to maintain the ants’ attention. These adaptations involves specialized organs that produce nutritional rewards or chemical signals to attract ants. The butterfly families Lycaenidae and Riodinidae provide many examples of myrmecophilous caterpillars, including species with these organs. In our recent study, published in Insectes Sociaux, we explored the impact of these specialized organs on ants by focusing on a species from the less-studied family Riodinidae, Synargis calyce, which interacts with various ant species. In our study area, the most frequent interaction involved the ant species Camponotus crassus.

Caterpillars of Synargis calyce interacting with different ant species. (a) With Camponotus crassus, (b) with Camponotus renggeri, (c) with Wasmannia auropunctata, and (d) with Paratrechina longicornis. ©Amalia V. Ceballos-González.

Caterpillars of this species possess two pairs of tentacular organs. The first pair, known as ATOs (Anterior Tentacle Organs), likely release volatiles that influence ant behavior, although there is insufficient evidence to confirm this. The second pair, known as TNOs (Tentacle Nectary Organs), secrete a nutritive substance (primarily composed by sugars and amino acids) that ants consume. Whether these organs work synergically or if one is more relevant than the other was still unclear for our study species and it is also the case for many other species of the family Riodinidae.

Illustration showing the position of the tentacular organs (TNOs and ATOs)  in a caterpillar of the Riodinidae family. Below, a photograph of Synargis calyce indicates the two pairs of tentacular organs with arrows (Yellow = ATOs, Blue = TNOs). Drawing adapted from DeVries (1991). ©Amalia V. Ceballos-González.

To uncover those aspects, we aimed to explore this pair of tentacular organs by checking ants’ reaction. Our research was conducted at the University of São Paulo, Ribeirão Preto campus. Our first objective was to create an ethogram documenting the behavioral interactions between caterpillars and ants. During these observations, we identified a striking behavior. The ethogram revealed that after the eversion of ATOs, ants exhibited stereotyped “jumping” behavior. This behavior involved ants rapidly lifting their legs and jumping towards the caterpillar’s head.

 Synargis calyce caterpillar interacting with a Camponotus ant.

Next, we conducted experiments in which we experimentally manipulated – by allowing or preventing them to evert – the two types of caterpillar organs (TNOs and ATOs), to determine their role in maintaining ant attendance. Our findings demonstrated that TNOs are more effective in maintaining the attention of attendant ants, likely due to the rewards these organs provide. However, we also found that caterpillars with only functional ATOs received more attention compared to those with neither organ functioning. This indicates that TNOs play a central role in sustaining ant-caterpillar interactions, while ATOs serve a complementary function.

Three caterpillars (possibly third instar) interacting with Camponotus ants.

In conclusion, the interactions between S. calyce caterpillars and attendant ants are primarily driven by the rewards produced by TNOs, with ATOs playing a smaller, supportive role. These findings are consistent with observations in Lycaenidae species, which exhibit similar mutually beneficial relationships with ants. The evolution of these organs may represent a case of convergent adaptation to environmental pressures experienced by caterpillars in both families.