Rhopalomastix ants feed on diaspidid scale insects inside living trees

A blog post highlighting the article  by Yong, Matile-Ferrero and Peeters in Insectes Sociaux.

By Christian Peeters

Many ant genera obtain honeydew from a variety of scale insects feeding on the sap of tropical trees. However, the most advanced and speciose scale insects – family Diaspididae – do not excrete honeydew, but build a protective shield made of wax and proteins and are known to associate with only one ant genus in Africa and Madagascar. The minute workers of Melissotarsus chew an extensive network of tunnels under living bark, and these are inhabited by vast numbers of diaspidids. Typically, these do not secrete the trademark shield when defended by ants, unlike free-living forms. Melissotarsus workers have extremely modified legs and cannot walk outside host trees, it is therefore assumed that they obtain all their food from the scale insects.

The Asian genus Rhopalomastix is strikingly similar in morphology to Melissotarsus, especially the bullet-shaped head of workers with the antennal sockets touching each other (in all other Myrmicinae, the antennal sockets are widely separated), and silk glands inside the head of adult females. However, the legs are normal, and a sting is retained. Molecular data confirm these are sister genera, sitting together on a separate branch. Rhopalomastix is widely distributed (India to eastern Australia), yet its biology was undocumented until Gordon Yong located it in Singapore. Four species nested in seven genera of living trees, together with five genera (one new) of diaspidids. Large numbers of naked diaspidids occurred in all ant nests, with only few shields.

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Heads of Melissotarsus and Rhopalomastix workers, showing how the antennal sockets meet in the center of the face (SEMs by Roberto Keller). Note that the Melissotarsus mandibles are strikingly abraded, indicating an old individual. The ventral expansion of the head accommodates large opener mandible muscles, a novel adaptation for chewing through healthy wood (Khalife et al. 2018). Image: Roberto A. Keller/AMNH

This mutualism is distinct from others involving ants and scale insects because of striking differences in the biology of diaspidids: (i) they feed on parenchyma cells, not the sap; (ii) adults are strictly sessile. First instars (‘crawlers’) disperse but once they have selected a feeding spot and insert their stylets, the legs and antennae degenerate. Thus, ants cannot regulate the distribution of diaspidids within their tunnels, instead the crawlers decide! Ant eggs are distributed throughout the tunnels and larvae feed autonomously, a character also found in attine ants where larvae feed on the cultivated fungus. We lack direct observations of feeding behaviour because the ants switch to other tasks once we exposed the tunnels. Do they eat the flesh of diaspidids? Or their milk (secretions of wax and proteins normally used to build the shield)? Probably both. Diaspidid exuviae are not found in the tunnels, suggesting that they are also eaten by the ants.

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Naked diaspidids (Andaspis numerata) and a few shields (green arrows) inside Rhopalomastix tunnels.

Trees hosting ants and scale insects generally benefit because the cost incurred from the ingestion of sap is compensated by the protection given by ants against leaf herbivores. This is not so in the mutualisms involving diaspidids with Melissotarsus and Rhopalomastix, because these ants are unsuited to be guards. Indeed, after removing bark and exposing tunnels, we observed that both workers and brood were preyed upon by Pheidole and Crematogaster ants. Field studies need to determine what is the impact on host trees, especially in fruit plantations (mangoes, durians, …) that are often preferred. Because only older trees are infested, we assume that these are more tolerant of the diaspidid exactions. Of special note is the host tree Aquilaria that is harvested commercially to produce an extremely valuable resin used for perfumes.

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Numerous naked diaspidids in galleries of Rhopalomastix from Thailand. Ant larvae are scattered along the tunnels.

Rhopalomastix is likely to be widespread throughout tropical Asia but it is necessary to scrape tree bark with a knife in order to locate nests. Previous collection events were restricted to pyrethroid spraying of tree trunks, and soil pit traps (hence they are often classified as ‘litter ants’). We have recently found their arboreal nests in Thailand, Borneo and the southerly Japanese island of Okinawa.

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Gordon Yong investigating a nest of Rhopalomastix on mango tree (Pulau Tekukor island, off Singapore).

References

Khalife A, Keller R, Billen J, Hita Garcia F, Economo E & Peeters C (2018) Skeletomuscular adaptations of head and legs of Melissotarsus ants for tunnelling through living wood. Frontiers in Zoology 15: 30.

 

Accessing the file drawer of experienced researchers: joint interviews with Bert Hölldobler and Robert Page

Every day, thousands of papers in various research fields are published. Some of them receive lots of attention, while others remain unnoticed. Simultaneously, thousands of studies are not even submitted to journals because the results are insignificant or the authors think the work does not add sufficient new knowledge to their research field. In these joint interviews by Insectes Sociaux and Myrmecological News, Bert Hölldobler and Robert E. Page Jr. share some interesting insight about their own research and why some studies did not result in papers. Here, you will read the interview with Dr. Robert Page. Also, check out the corresponding interview with Dr. Bert Hölldobler!

Founders Day-Robert Page

IS: Dr. Page, as you look back on (and are still proceeding with) a fantastic career in social insect research, roughly how many papers have you published so far?

RP: I have published about 250 papers so far, including reviews and book chapters.

IS: Which of your papers received the most widespread attention? Did you expect this?

RP: The honey bee genome sequence paper in Nature in 2006 is by far the most cited, but I was one of a million authors, and it is basically a resource paper. I expected it to be the most cited.   Next is the Cell paper I published with Martin Beye in 2003.  I also expected it to be cited a lot because it is probably the most important paper I’ve been a part of.  It also represents a long hard struggle in my lab and Martin’s spanning about 7 years, and a question I actually started working on in 1980.  My 4thmost cited paper is one I published in Experimental Gerontology with Christine Peng in 2001.  It was a review article on a subject I knew little about but was picked up and has been cited 300 times.  I never would have figured that.

IS: Have you published any papers that you think received insufficient attention from the scientific community? If so, can you give us an example?

RP: I have several, but I know why they didn’t receive the attention I thought they should.  I tend to undersell my work.  I don’t go for high impact journals, just because they are high impact.  I try to publish in the journal that is appropriate for the audience I am trying to reach.  Often that is an audience of specialists.  I also tend to publish places that let me present all of the data and methods.  In the long run, the ability to repeat someone else’s work is the hallmark of science, and you need to provide your data.  And, hypotheses and current trends in what is perceived as exciting science come and go, but bad data stand forever.  So, I try to present all of the data as best I can so they can stand whether my ideas do or not.

IS: What do you think is the main reason well-designed studies go unnoticed by the scientific community?

RP: Science today is like a collection of infomercials.  If you don’t package it right and sell it in the right venue, it goes unnoticed.  I guess I am an old fogey about this, but I believe it.

IS: Have you completed studies of which you have not published the results even though you consider them relevant? To how many projects or datasets does this apply over your career, approximately?

RP: Yes of course. I don’t believe in “do an experiment, write a paper.”  The objective of science in my mind is to contribute to an understanding of something. Sometimes experimental results obfuscate our understanding, not improve it.  Usually, more experimentation will fit the pieces together and lead to an understanding, but sometimes you don’t get back to it, so it sits in the filing cabinet, or in an electronic file on your computer desktop.  I have many incomplete studies sitting there.

IS: Do your unpublished datasets have anything in common? Why did you not publish them? Was it ever due to a lack of statistical significance?

RP: As I said in the previous question, it is usually because I can’t figure out how the results fit into a bigger understanding.

IS: Does the field of social insect research generally suffer from gaps due to data not being published?

RP: No, I think too much is published too soon.  We would be better off with fewer papers that actually resolve something.

IS: What do you think is the general trend over time concerning the amount of unpublished data? Stable, decreasing, increasing?

RP: I really don’t know about other people.  I think mine increased over time because as I got older and had more of a focus on specific questions that I wanted to answer, I became more demanding that each paper contributed to an understanding.

IS: Would you be willing to share any or all of these unpublished data so that others could learn from them or profit in any other way? If so, what might be a good platform for this? Do you think that, for example, a database could be set up for such data?

RP: That is a difficult question.  My idea about bad data lasting forever actually came from Darwin.  Often there are reasons data don’t get published, often it is a lack of confidence in them.  Something peculiar in the methods, or an environmental anomaly when the experiment was conducted.  I don’t think any data should be shared on a public platform that isn’t completely reliable and carefully screened.  If you do that, you should write the paper.

Book Review: The Ants of Central and North Europe

By Heike Feldhaar (University of Bayreuth, Germany)

Seifert Ants of Central and North Europe

Many people are fascinated by ants and their behaviour. Even children will often recognize these little busy-bodies that always seem to be determined to pursue their work. Ants have captured the attention of many hobby entomologists. At least in temperate regions of the world, they are an attractive and manageable group in terms of species number. However, species identification of ants is often difficult; in comparison to other insects, ants have seemingly fewer characters for easy identification, such as colour patterns of butterflies or bumblebees. Several ant genera, such as the Holarctic Lasius, Myrmica, or Formica, contain species that even professional myrmecologists have trouble identifying. Only a few very conspicuous ant species, such as Dolichoderus quadripunctatus or Lasius fuliginosus can be identified easily without magnifying glasses; many require some type of optical equipment. In the field, notes on the structure of nests or habitat features help to narrow down species identity.

A good guidebook should, therefore, include a workable key for species identification as well as an informative natural history section with detailed pictures. Bernhard Seifert’s The Ants of Central and North Europe (2018) provides precisely that. The book is divided into two major parts: a “General Part“ with an overview of ant natural history and ecology, and a “Special Part” with a key to all 180 species (for gynes and workers) occurring outdoors in Central and Northern Europe (and a few more that may expand their range into the region) and detailed natural history information for every species. Here, I describe the contents of these two parts in more detail.

The “General Part” (translated into English by Elva Robinson) comprises short chapters on the general morphology of ants, ecological aspects such as their habitats and nests, colony foundation and life cycles of colonies, social parasitism, natural enemies of ants, and feeding strategies. These feeding strategies include interactions of ants with trophobionts for honeydew consumption and seed dispersal by ants. This general part may be skipped by professional myrmecologists that are familiar with the general biology of ants and the corresponding terminology. For beginners, it lays the foundation for understanding the “Special Part” in which Seifert provides natural history details for every species.

The “Special Part” begins with a short introduction to ant determination and mounting, a list of the covered ant species (with a focus on Germany, Switzerland, Austria and South Tyrolia), a checklist of German ants with information on their distribution within Germany (occurrence in federal states, vulnerability and broad ecological niche), and an overview of their ecological preferences and tolerances. This table covers ~ 90 of the 180 ant species and is based on over 200 plots studied by Seifert in Central Europe during the years 1979–2015. It provides detailed information on temperature and humidity preferences and occurrence patterns with respect to plant cover. Thus, the three tables focus on the area where Seifert was most active himself, and less information is available on other areas of the geographic range covered in the book, such as Fennoscandia, Great Britain or Northern France. However, Seifert lists occurrences and ecology of species in these areas in the detailed species accounts. This part is followed by three short chapters where Seifert discusses methods of taxonomic delimitation of species (morphology vs. genetics), justifies the method used by him, numeric morphology-based alpha-taxonomy (NUMOBAT), and defends Linnean binomial nomenclature. These three chapters are part of an ongoing debate among taxonomists, and amateur myrmecologists will most likely skip these four pages.

Seifert then provides an identification key from subfamily to species level (for gynes and workers) for the 180 ant species with outdoor occurrence and nine Mediterranean species that will likely expand their range into Central and Northern Europe due to climate warming. Tramp species are also included, which are mostly found in warm buildings such as larger greenhouses. The key is illustrated with line drawings for many characters that allow for easy comparison of different character states. These drawings might be challenging for beginners, such as the detailed drawings of antennal scapes viewed from different angles of Myrmica workers, but once the reader has grasped the concept, these drawings are very helpful and allow identification to species level. The key works well for slightly advanced ant enthusiasts for the majority of species. For a few species, optical equipment with a micrometer is required; this will not be available to most amateurs, but this is a hurdle in all insect groups and not a failing of this book.

The key is followed by a detailed description of the life histories and profiles of all ant species covered in the book. Bernhard Seifert provides detailed information on the geographic range, habitat and ecology, abundance and nest structure, colony demography and population structure, as well as nutrition and behavior of all species (if known!). These natural history notes are beneficial to beginners and professionals alike. They contain most of the basic information known for each species and are referenced very well, which allows an interested reader to quickly find more details for each species (the reference section contains more than 1,000 references!). Thus, the book is a great starting point for myrmecologists who want to know about the natural history of a particular ant species. The life history and reference sections are substantially extended in comparison to the German book Die Ameisen Mittel- und Nordeuropas, which appeared in 2007 (Lutra Verlags- und Vertriebsgesellschaft), making it not a mere translation of the former.

Students, amateur myrmecologists, and specialists will appreciate Bernhard Seifert’s The Ants of Central and North Europe. The “General Part” provides an excellent overview of general ant ecology and natural history to enthuse amateur myrmecologists, whereas the keys might be challenging for beginners but are very helpful for specialists as they allow the identification of most ant species occurring in Central and North Europe. The extensive information on each ant species makes it an essential reference about ants in this geographic region for all interested readers – from beginners wanting to know more about ants to professional myrmecologists.

 

SAMSUNG CSC

Heike Feldhaar

 

Reference

Seifert, B. 2018. The Ants of Central and North Europe. – lutra Verlags – und Vertriebsgesellschaft, Tauer, Germany, 408 pp; ISBN 9783936412079 (hardcover), EU € 64.00.

In termites, the evolution of alate body size caught between two opposing selective forces

A blog post highlighting the article by T. Chouvenc in Insectes Sociaux

By Thomas Chouvenc

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Alates of Coptotermes gestroi emerging during a dispersal flight event, with soldiers guarding the exit holes.

Sexual selection and partner choice have been hot topics in behavioral ecology over the past few decades, as scientists have been investigating impressive cases of sexual dimorphism and extreme attributes both in vertebrates and arthropods. In some social Hymenoptera, the males are often reduced in size and function compared their female counterparts. The need for a massive accumulation of metabolic reserves in these males has decreased over evolutionary time as their role has been reduced to simple yet functional sperm missiles. In termites, such extreme reduction of the male size is not present (despite cases of significant sexual dimorphism): both the female and male are essential during colony foundation as they provide exclusive monogamous biparental care within the first few months of the life of the colony. The royal couple will then spend years, sometimes decades together, contributing solely to reproduction. One might argue that such lifestyle should promote the evolution of ‘picky’ mate selection.

However, during the dispersal flight and colony foundation of termites and many other eusocial insects, the potential for partner selection may be minimal due to the chaotic nature of mating swarms, when individuals only have a few minutes to find a partner and create an incipient colony or die. My anthropomorphic self likes to see it as an extreme form of speed dating. This mating behavior implies that being too choosy in mate preference would be counter-selected, especially when predation pressure is high. However, some lines of evidence suggest that ‘high quality’ primary reproductives could experience improved mating success, survival traits, fertility, and ultimately colony foundation success. Hence, despite an overall absence of mate selection, there could still be passive evolutionary selection for alate size or quality.

In termites, two main opposing selective forces may drive the evolution of the overall alate body size during colony foundation events.

The first selective force, as outlined by Nalepa (2011), is inherent to the biology of termites. Both the king and queen are monogamous partners, and each contributes to the biparental care of their first cohort of offspring. However, as the first functional workers emerge, the brood care duties irreversibly shift to the workers, resulting in constant alloparental care as the queen and king lose their ability to provide care for their brood (Chouvenc and Su 2017). Nalepa argued that in incipient termite colonies, the rapid switch from biparental care of the first brood to alloparental care of subsequent brood has resulted in reduced selection for the accumulation of large metabolic reserves in imagoes. As evidence for this, queen and king fecundity is maintained despite a relatively small body size (when compared to their ancestral wood roaches). The directional reduction of body size in termite imagoes may, therefore, have allowed mature termite colonies to increasingly invest into the number of alates to optimize their dispersal success rate.

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Young Coptotermes formosanus colony, where the workers have already taken over parental care duties.

The second selective force is opposite to the first one, as the limited metabolic reserves of relatively small termite alates during colony foundation leaves little room for inefficiency. The quality of the first brood is important for colony foundation success and the initial input from the queen and king are critical to jump-start the colony and improve its long term success within a highly competitive environment. Such pressure might incentivize mature colonies to invest in high-quality alates with enough internal metabolic resources to successfully produce their first cohort of functional workers during the incipient colony phase.

In dispersal fight events, Coptotermes gestroi alates may rapidly be killed by a wide range of predators. In this video, Pheidole megacephala was able to capture most alates that landed on trees or on the ground, which show how luck can be an essential factor on alate survival, independently of the quality of individuals.

In my 2019 study, I was able to take advantage of large dispersal flight events of Coptotermes gestroi (Rhinotermitidae) with high intracolonial and intercolonial variability in size to test the actual role of alate body size in colony foundation success and growth within the first nine months after foundation. I was able to measure 79% colony foundation success (n = 175), and most colonies that failed to establish had relatively small males and females, suggesting that mated pairs with relatively large individuals had a higher chance of surviving the first few months. This data suggests that, although the rapid transition to alloparental care in incipient colonies might reduce the need for accumulation of substantial reserves in alates, the mated pair still requires a bare minimum of initial metabolic resources to initiate efficient colony foundation and provide biparental care. Also, a positive correlation between the initial king and queen weights and colony growth was found despite high colony growth variability. Both the king and the queen initial weights were relevant for colony growth when considered separately, confirming the importance of biparental care, but when combined, only explained 27% of the observed variability despite highly standardized rearing conditions.

This study confirmed that during colony foundation in laboratory conditions, the initial weight of C. gestroi females and males plays a role in colony foundation establishment and initial colony growth rates. However, such laboratory results need to be placed in the perspective of the harsh conditions of field dispersal flights, where the vast majority of alates die rapidly and founding conditions are highly heterogeneous and hazardous. Therefore, the importance of alate weight may be secondary to many other environmental factors and luck. As previously suggested (Hartke and Bear 2011), sexual selection for large alate body size in termites during and after dispersal flights may be extremely weak and secondary to a wide variety of other selective pressures.

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Alates of Coptotermes gestroi emerging from a tree trunk by the thousands and ready to fly out.

Mating flights in C. gestroi termites can comprise hundreds of thousands of alates, and the large number of alates produced may be more relevant to the final number of established incipient colonies than the marginal advantage that relatively large alates may have during colony foundation. Such a reproductive strategy primarily relies on “inundative” dispersal flights, which may also have reduced the importance of alate weights during colony foundation. The trajectory of the reproductive strategy of a given termite species may partially be reflected in the size of their imagoes, an investment into reproduction which reflects the life history of the species. Over evolutionary time, termite colonies have optimized this quality/quantity trade-off in alate production, which varies among species.

In the light of its remarkable invasive abilities and its high colony establishment rate in the laboratory, C. gestroi may be a termite species that is able to efficiently optimize such balanced investment and adapt to various environmental pressures during dispersal flights and colony foundation.

References

Chouvenc, T., & SU, N. Y. (2017). Irreversible transfer of brood care duties and insights into the burden of caregiving in incipient subterranean termite colonies. Ecological entomology, 42(6), 777-784.

Chouvenc, T. (2019). The relative importance of queen and king initial weights in termite colony foundation success. Insectes Sociaux, 1-8.

Hartke, T. R., & Baer, B. (2011). The mating biology of termites: a comparative review. Animal Behaviour, 82(5), 927-936.

Nalepa, C. A. (2011). Body size and termite evolution. Evolutionary Biology, 38(3), 243-257.

Behind-the-scenes of the Insectes Sociaux best paper 2018

A blog post highlighting the article that received the prize for the best paper published in Insectes Sociaux in 2018 by Paul J. Davison and Jeremy Field.

By Paul Davison and Jeremy Field

 

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Jeremy at a Lasioglossum malachurum nest site in Spain

Paul’s Ph.D. focussed on the unusually varied social biology of sweat bees, which include eusocial species, solitary species and also socially polymorphic species. In socially polymorphic sweat bees, some populations have eusocial nests with a queen and workers, while in other populations of the same species all nests are solitary. Solitary populations are always found at cooler latitudes and/or higher altitudes than eusocial populations. Likewise, obligate eusocial species, in which nests always have queens and workers, never occur at the coolest latitudes or higher altitudes alongside solitary species or populations. The main element of the Ph.D. involved performing a field transplant to explore how the environment influences behaviour in a socially polymorphic sweat bee (for the results, see Davison & Field (2018) Behavioral Ecology & Sociobiology 72:56).

 

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A Lasioglossum malachurum foundress resting by the entrance to her new nest in spring

 

We thus became interested in what limits the geographic distribution of eusociality in sweat bees. It has long been thought that once the growing season becomes too short, it is no longer possible to sequentially produce the successive worker and reproductive broods necessary for eusociality and the only option is solitary nesting. Noticing that this had not been tested experimentally, we thought it would be interesting to do just that. The best way would be to conduct another transplant, only this time of an obligate eusocial sweat bee far to the north of its natural range.

 

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Freshly removed buckets containing newly dug nests ready to be packed for transplant

 

We chose to transplant Lasioglossum malachurum, a well-studied obligate eusocial sweat bee that is restricted to the south and east of Britain. We wanted to investigate the reasons for this, and in particular whether it is related to the length of the season. Because of other fieldwork commitments, this project would have to be ‘smash and grab’, or ‘smash and transplant’. Jeremy had the ingenious idea of getting spring foundresses to nest inside plastic buckets and then transplanting them and their nests wholesale. To do this, we spent winter digging trenches adjacent to where the bees nested in southern England, filling buckets with the excavated soil then putting them back into the trench and filling in the gaps. In essence, digging holes and filling them in again! By transplanting buckets after nests had been initiated in spring but crucially before foundresses began provisioning, we could test how being in a northern environment with a shorter season would impact the eusocial lifecycle.

 

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Embedding buckets in the garden of the University of Aberdeen’s Lighthouse Field Station at Cromarty (Photo: Paul Davison)

 

We were generously allowed to embed our transplanted buckets in the garden of the University of Aberdeen’s Lighthouse Field Station at Cromarty in northern Scotland. Cromarty is much further north than where L. malachurum occurs naturally and is a place most people have only heard of thanks to the BBC Radio 4 shipping forecast. Nestled between the 1840s lighthouse and stunning Cromarty Firth, the bees would certainly have a good view if nothing else. Equally generously, since it involves hours of scraping away at a block of soil on a table and is incredibly messy, Paul was able to excavate the buckets in rooms owned by the Cromarty Arts Trust. We transplanted control buckets to the University of Sussex campus, well within the bee’s natural range. All that remained was to see whether driving the length of Great Britain with buckets of nesting sweat bees would pay off.

 

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Digging a hole adjacent to the Lasioglossum malachurum nest aggregation in southern England for embedding buckets (Photo: Paul Davison)

 

The results were unequivocal. When we excavated the nests eight weeks after transplanting them, first brood offspring at Sussex were all nearing the completion of development, whereas in Scotland most offspring were still tiny larvae that had not long hatched. We estimated that this represented a lag of approximately seven weeks behind Sussex and that, had they been left to complete development, the first brood in Scotland would not have emerged as adults until August! This would leave no time for workers to provision a reproductive brood successfully. We found that the time lag corresponded to differences in temperature, which is well known to influence the timing of bee activity and seems to have caused foundresses in Scotland to begin provisioning much later in the spring. Importantly, this reflects environmental constraints on provisioning behaviour rather than the strategic shift between social and solitary nesting seen in some socially polymorphic sweat bees (Field et al. (2010) Current Biology 20:2028-31).

 

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A Lasioglossum malachurum nest entrance with a red marked female sitting just inside the entrance

 

All in all, some intriguing results. Jeremy is planning to take this initial work further with more replicates and a detailed study of what exactly causes the time lag.

Red wood ants stalked by a Trojan horse

Highlighting upcoming research from Thomas Parmentier entitled ‘Host following of an ant associate during nest relocation’, to be published shortly in Insectes Sociaux

Even more fascinating than ants, is the extremely diverse group of arthropods that live strictly in their nests. Gradually, we learn that these creatures, commonly  referred to as myrmecophiles or ‘ant loving’, possess an array of chemical, morphological and behavioural adaptations to by-pass ant aggression and to make a living in the hostile nest environment (Kronauer and Pierce 2011). Many myrmecophiles are parasites that feast on a lavish banquet of brood and other resources found in the nest (Parmentier et al. 2016a).

What is rather unknown so far, is how myrmecophiles move in the landscape and target new nests. It can be expected that myrmecophiles are prompted to colonize new nests, when nest conditions start to deteriorate or when competition with other myrmecophiles becomes too strong. During my current postdoc project, I study the spatial dynamics of myrmecophiles associated with European red wood ants. These ants are famous for their large mound nests and aggression, yet their nests harbour a rich community of myrmecophiles (Parmentier et al. 2014).

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Last spring, I visited a study site in the north of Belgium and to find out whether the wood ant colonies (Formica polyctena) made it through the winter and whether new nests were founded. Then, I observed that one colony was moving to a new nest site a couple of metres away. As I have been curious for a long time how myrmecophiles would respond to the desertion of their home, I carefully inspected the horde of moving workers. To my surprise, I saw that a group of larvae of the beetle Clytra quadripunctata (Chrysomelidae) were crawling among the moving colony towards the new nest site. A bit later, some larvae were also dragged by the workers to the new nest. Luckily, these days, smartphones are equipped with rather decent cameras, so I was able to record this rare event. There are some old and anecdotal notes which suggest that some myrmecophiles are also able to track their host during relocations to a new permanent nest site, but this has not been recorded so far.

The biology of Clytra quadripunctata is rather peculiar. The adults are adorable beetles that feed on plants near the nest. After mating, the female drops her eggs. The larvae enter the nest and remain there probably for 2 years (Donisthorpe 1902). Lab tests demonstrated that the larvae are brood predators and scavengers. They preferentially reside in the heated brood chambers in the centre of the nest (Parmentier et al. 2016b). The larvae of this beetle are protected by a pear-shaped case in which they can retract. After pupation, the adults sneak out of the ant nest.

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My observations suggest that the beetle larvae adaptively respond to rare nest-moving events. Interestingly, they can find the new nest site on their own or be carried by workers unaware of the danger that is hiding in the case. Nonetheless, a significant fraction of the larvae did not find the new nest and remained in the abandoned nest. Wood ants are thought to move occasionally when microclimatic conditions become suboptimal. However, they may also be triggered to relocate to a new nest site in order to reduce parasite load. This could end up in an evolutionary arms race where the host will move more frequently and more distantly, whereas the parasite will develop more advanced strategies to follow or locate its host. This is a tempting hypothesis that deserves further research.

This observation has galvanized me to unravel some more secrets of myrmecophile dispersal the coming years. More information on the progress of my research on myrmecophiles can be found at:

https://www.researchgate.net/profile/Thomas_Parmentier

 

Donisthorpe HSJK (1902) II. The Life History of Clythra quadripunctata, L. Trans R Entomol Soc London 50:11–24.

Kronauer DJC, Pierce NE (2011) Myrmecophiles. Curr Biol 21:208–209.

Parmentier T, Dekoninck W, Wenseleers T (2014) A highly diverse microcosm in a hostile world: a review on the associates of red wood ants (Formica rufa group). Insectes Soc 61:229–237.

Parmentier T, Bouillon S, Dekoninck W, Wenseleers T (2016a) Trophic interactions in an ant nest microcosm: a combined experimental and stable isotope (δ13C/δ15N) approach. Oikos 125:1182–1192

Parmentier T, Dekoninck W, Wenseleers T (2016b) Do well-integrated species of an inquiline community have a lower brood predation tendency? A test using red wood ant myrmecophiles. BMC Evol Biol 16:12.

 

2018 Highlights from Our Community

Hello, social insect community!

2018 was productive for the social insect community, especially for Insectes Sociaux. As the new Social Media Editors, we have been enjoying collaborating with many social insect scientists on blog posts. Thank you for your contributions not only to making our journal great but also our blog, whether that’s through reading or writing! As 2018 came to an end and we were reflecting on the year, we reached out to past blog contributors to see what they’ve been up to. Here are some 2018 highlights from social insect scientists:

Kaitlin BaudierPostdoctoral Research Associate, School of Life Sciences, Arizona State University

You can find Dr. Baudier at kmbaudier.weebly.com and @AntGirl_KB. She also has a YouTube channel.

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IS: What is the most exciting thing you’ve learned about your study species in 2018?

KB: On the army ant front (pun intended) I learned a lot about bivouacs in 2018. It turns out that bivouacs of the most well-studied army ant (Eciton burchellii) do not strictly thermoregulate as was previously thought. At high elevations, we found that bivouacs selected different thermoregulatory strategies dependent on brood developmental stage. When ambient temperatures were low and bivouacs were filled with predominantly larvae, bivouacs would allow energy-conserving cooling. However, bivouacs rich in pupae were always kept warm regardless of ambient temperature. We report on this energy-saving strategy for coping with high elevation cold temperatures in our recent paper in Ecography. This was an interesting turn in our bivouac elevation project which we first published in Insectes Sociaux back in 2016.

2018 also marked my first work on the topic of nest defense in the stingless bee Tetragonisca angustula. This species is famous for having two types of nest entrance guards: hovering and standing guards. In our paper currently in revision at Behavioral Ecology, we report that task allocation between these two guarding jobs is age-dependent, with younger bees hovering guarding and older bees standing guarding. This was an unexpected and exciting finding in our study which had initially set out to collect task allocation data for a bio-inspired design project aimed at improving defensive swarm algorithms in unmanned aerial vehicles (Strickland et al. In Press). We also found that roaming Ectatomma tuberculatum ants use sit-and-wait predation to make a meal of these guard bees. Life for a guard bee can be rough.

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IS: What was your favorite conference and/or fieldwork experience?

KT: IUSSI 2018 in Brazil really blew the top off of my idea of what a great conference could be. Not only did I get a chance to speak with a multitude of established social insect biologists from around the world, but it was an excellent opportunity for me to meet a lot of amazingly dedicated students and to learn about their respective projects. I walked away from Brazil 2018 with more than a few new collaborators. As for fieldwork, I have been having an extremely positive experience working with the Smithsonian Tropical Research Institute in Panama this past year. From my fieldwork in and around BCI and Gamboa to my returning to co-instruct the ASU Tropical Biology course at STRI in the summer, I have enjoyed getting to know the insects, the people, and the environment in Panama. As 2019 begins, I am already packing my field equipment for another trip back. Some days I can’t help but think that it doesn’t get any better than this.

 

Rachael BonoanPost-Doctoral Researcher, Tufts University and Washington State University

You can find Dr. Bonoan at www.rachaelebonoan.com and @RachaelEBee.

IS: What is the most exciting thing you’ve learned about your study species this year?

RB: This year, I started a post-doc studying the natural history of an ant-caterpillar relationship in a Pacific Northwest prairie. When it’s a caterpillar, the Puget blue butterfly, is protected by ants. In return for protection, the caterpillar secretes a sugary snack for the ants. As mentioned in my Interview with a social insect scientist, part of my job is to figure out which ants live on the prairie with my Puget blue caterpillars.

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With the help of two Tufts University undergraduates, Hanna Brush and Max McCarthy, we have identified ten species of ants on our field site! (Many thanks also go out to Stefan Cover at the Harvard Museum of Comparative Zoology and Chad Tillberg at Linfield College for help identifying and pinning specimens.)

So far, there are two dominant ant species on our prairie: Formica obscuripes (the Western thatch ant) and Tapinoma sessile (the odorous house ant). We have seen both tending Puget blue caterpillars, this bodes well for the baby butterflies!

The most exciting species we identified, however, is Ployergus mexicanus, also known as the raider ant or the pirate ant. The raider ant has sickle-shaped mandibles (mouthparts) specialized for kidnapping young from other ant colonies. The ultimate moocher, this ant species cannot feed itself or take care of its own young.

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After mating, a female raider ant infiltrates the colony of another ant species, typically a Formica species. The female raider ant subdues Formica workers with a specialized pheromone and promptly overtakes their queen. With the Formica queen out of the way, the raider ant queen is ready to begin her reign—she lays eggs that the Formica workers raise. With the help of their sickle-shaped mandibles, raider ant workers spend their days raiding other Formica colonies and kidnapping their young. This ensures that there will always be enough Formica workers to raise more raider ant workers.

IS: What was your favorite conference and/or fieldwork experience?

RB: This year, I attended two great conferences: Entomology in Vancouver, B.C. and Social Insects in the North East Regions (SINNERS) in Philadelphia, PA. While I enjoyed both conferences, SINNERS was held at the coolest conference venue: the Natural Academy of Sciences of Drexel University (a museum!). During the meeting, the museum had a fantastic exhibit: Xtreme Bugs! This exhibit celebrated “extreme insects” with giant, animatronic models of the amazing beats. My favorites were, of course, the leafcutter ants and the honey bee!

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Excellent venue aside, SINNERS is one of my favorite conferences. This relatively small conference (~50 speakers this year) gives you the opportunity to get to know social insect scientists! Since it’s a regional conference, SINNERS also a great meeting to find nearby social insect friends and collaborators. I met James Waters at SINNERS 2015, and we have continued to stay in touch! James and his students have visited my honey bees at Tufts (they even lent us a wireless temperature sensor for my research), and I have given a couple guest lectures in James’s classes at Providence College!

 

Tomer CzaczkesACElab Group Leader, University of Regensburg

You can find Dr. Czaczkes at animal-economics.com and @tomerczaczkes.

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IS: What is the most exciting thing you’ve learned about your study species this year?

TC: We started trying to train Drosophila to associate odours with food qualities. Man, those things are thick as glue! It gave me a real appreciation for our study species, Lasius niger – we found that these ants can learn an odour / food quality association reliably after just one exposure. I admit that perhaps the flies could learn that quickly if one used precisely the right method. Perhaps. So maybe rather than being thick, they are fiddly and delicate. Really makes me appreciate how robust and easy to work with our ants are.

 

The Insectes Sociaux editors have also been curious about our social media followers. To learn more about the kinds of scientists in our Twitter community, we recently put out a series of polls. Overall, we’ve learned that most of our followers study behavior and bees, and wish they had more time for fieldwork. Here are the results!

 

“We know all social insects are great, but what is your favorite?”

41% Bees

40% Ants

12% Wasps

7% Termites

 

“What do you predominantly study?”

51% Behavior

18% Ecology

6% Morphology

25% Combination of all of the above

 

“What component of your work do you wish you had more time for?”

49% Fieldwork

35% Publishing/writing

8% Teaching

8% Outreach / science communication

 

What have you been up to recently with your science? Do you have a comment or suggestion for our blog, social media presence, or journal? We would love to hear from you! Follow us and send us a message through Facebook, Instagram, or Twitter.

Happy new year! We hope you have fulfilling scientific endeavors in 2019.

Madison Sankovitz & Bernie WittwerSocial Media Editors, Insectes Sociaux

 

A high-speed camera reveals a new behavior of honey bees

A blog post highlighting the article by S. Łopuch & A. Tofilski in Insectes Sociaux

By Sylwia Łopuch and Adam Tofilski

 

The behavior of honey bees (Apis mellifera) still contains a plethora of mysteries. After many decades of research, bee communication is still not entirely understood. Efficient communication is particularly important for social insects such as honey bees because a single colony consists of tens of thousands of bees that need to cooperate to survive.

A high-speed camera may be beneficial to the study of social insect communication because it can record thousands of frames per second. As a result, high-speed video recording lets us see details that are undetectable to a human eye.

Observations of a few colonies of honey bees with the use of a high-speed camera revealed that the bees moved their wings in temporal and behavioral patterns within the nest. We housed colonies in observation hives (which consisted of two frames with bees placed behind glass walls) and recorded the bees’ behavior. The wings remained motionless most of the time. However, occasionally bees with folded wings performed a few wing beats. Interestingly, this behavior was observed not only in workers but also in queens and drones. The wing movements were detected most often during the swarming season (the reproduction period for honey bees). The queens performed this wing behavior only at that time. Similarly, drones vibrated their wings only during preparation for mating flights and when they were evicted from the nest by workers. The wing movements were observed most often in workers, which moved them both during the swarming season and outside of it (video). Workers moved their wings when they were in contact with a queen or another worker, including workers returning to the nest with food (pollen or nectar) and those guarding the nest entrance.

Our observation that the honey bees moved their wings when they were in contact with other bees led us to assume that the function of the wing movements is related to communication. We also recorded wing movements of dancing bees. Workers perform the waggle dance when they find an attractive source of food. After they return to the nest after foraging, they dance to transfer information to other nestmates about the location of the food source. It is possible that frequency of wing beats (the number of wing beats per second) and duration of episodes of wing beating transfer some information because these metrics significantly differed in queens, drones, and workers. The characteristics of the wing movements also depended on temporal context, differing in the swarming and non-swarming seasons. Therefore, wing movements may support communication based on vibrations in the darkness of nests where visual cues are ineffective.

In conclusion, high-speed video recording allows us to observe unknown behaviors of honey bees like wing movements and help us better understand their meaning.

Interview with a social insect scientist: Jan Šobotník

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IS: Who are you and what do you do?

JS: My name is Jan Šobotník, and I am an Associate Professor at the Faculty of Forestry and Wood Sciences, Czech University of Life Sciences in Prague (Czech Republic). I am the head of the Termite Research Team (see https://termiti.fld.czu.cz/en/or https://www.facebook.com/TermiteResearchTeam/), a group of researchers and students working on the ecology of termites at the global scale.

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

JS: I began my research by studying the physiology and chemical ecology of termites, and gradually shifted into field research. I am always amazed by the incredible intricacy of tropical ecosystems and the role of termites as key players in these ecosystems.

IS: What is your favorite social insect and why?

JS: I am truly fascinated by the contrast between the vulnerability of termites and their dominance in tropical ecosystems – at our plot in Cameroon, there are about 5,000 termites per square meter! They function as ecosystem engineers, moving tons of material per hectare and year and fundamentally influencing not only terrestrial biomes but, through the release of greenhouse gases, the temperature at the global scale. However, when their environment becomes less controlled, they quickly become prey or die in a Petri dish within tens of minutes!

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

JS: I really enjoyed the work we did on Neocapritermes taracua. It is a common soil-feeding termite in French Guiana, and we described incredibly complex defensive mechanisms in workers. At the beginning of this work we didn’t know much about them, but we knew that we were dealing with a fascinating system. We have continued working with N. taracua in order to reveal as much as we can about their colonies.

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

JS: I participate in all these activities to a variable extent during the year, and, among others, I helped to create a documentary movie, “The World According to Termites”, which has been successful at documentary movie festivals such as Life Science Film Festival 2017 (major award) and Wildlife Vaasa Festival (winner of the science category).

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

JS: I think it is important to understand the evolution of eusociality. This research has been furthered by the rapid development of new sequencing tools, allowing us to study proximate developmental mechanisms and also infer new phylogenies of unprecedented resolution. Another important research question concerns the ecological performance of particular species: What makes some species more ecologically successful and others? These questions are fundamental and will help us understand which species are the most endangered by ongoing global changes!

Concerning future research, it is critical to reduce the negative impact of the human population on natural resources. Social insect habitats are being decimated by anthropogenic effects, which means that future scientists will not be able to study social insects in the same ways we do today.

IS: What research questions generate the biggest debate in social insect research at the moment?

JS: There is a little doubt that the modern sequencing approaches are changing science more than any other methods implemented in the past. So, in my opinion, the hot topic (beyond just social insect science) is how to deal with large datasets produced by new sequencing platforms.

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

JS: I recently finished reading Sapiens: A Brief History of Humankind by Yuval Noah Harari. I think it provides an excellent survey of anthropogenic impact on the Earth. It is a distressing read, but I highly recommend it for people who are able to change their lifestyle.

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

JS: I like photography, especially insect macro photography, although I do not have much time to play with insects outside of field work. Additionally, I recently moved to a house in a village close to Prague, so I am trying to create an enjoyable garden for my family and me along with a small biodiversity hotspot with plants blossoming throughout the year, a water source, dead wood, open soil, etc.

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

JS: I try to stay on top of things, not take the challenges too seriously, and not consider myself too important. Also, of course, I take comfort in my family, kids, and friends.

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

JS: Professors from my studies and colleagues from universities and research centres have had the most considerable influence. Surely my ex-supervisor, late Prof. Pavel Štys, to name at least one.

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

JS: Never give up! It might be hard, but if you work hard, read a lot, and follow your dream, you will be successful!

Interview with social insect scientists: Kaleigh Fisher and Mari​ West

Kaleigh and Mari are authors of the recently published review article, ‘Are societies resilient? Challenges faced by social insects in a changing world’.

 

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Kaleigh Fisher doing fieldwork in Chiapas, Mexico

 

 

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Mari West

 

IS: Who are you and what do you do?

KF: I am a graduate student in the Woodard lab at the University of California, Riverside. I am using methods from insect behaviour, evolution, and sensory ecology to understand how taste operates in bumble bees.

MW: I am a 3rd-year graduate student in the Purcell Lab in the Entomology Department at the University of California, Riverside. I study non-reproductive division of labor in ants, with the goal of understanding how continuous size variation and differences in chemical cues among workers affect how tasks are partitioned in social insect colonies.

 

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Kaleigh Fisher doing fieldwork in Chiapas, Mexico

 

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

KF: I was interested in agroecology and started working in a lab that studies insects in shade coffee farms in Mexico. I became interested in the ants and the stingless bees in this system. The research was super exciting; it was my first introduction to social insects, and I have been working with them ever since.

MW: I first became interested in social insects as an undergraduate at Cornell University, where I worked in Dr. Linda Rayor’s lab, studying behavioral dynamics between reproductive females in social spider colonies. These spiders are usually very tolerant of each other but can become quite aggressive (to the point of being cannibalistic) when vying for reproductive opportunity. Later, while working with an invasive ant species that is highly polygyne and super-colonial, I realized that there was a vast spectrum of cooperative behaviors within social groups. Since this realization, I have been interested in how social insects can coordinate these collective behaviors without any central control.

IS: What is your favorite social insect and why?

KF: My favorite social insects are the stingless bees. They are so interesting both biologically (eusocial, ~500 species) and culturally (long history of stingless beekeeping in Mexico). I worked with them briefly before starting to work with bumblebees and hope to have the opportunity to work with them in the future.

MW: Why do I have to have a favorite? They’re all awesome in their own ways.

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

KF: I think the best moment in my research so far happened a few weeks into my first field season on a shade coffee farm in Mexico for my master’s research. I stopped and thought, “wow this is awesome, I can’t believe this is my job!” It’s easy to get overwhelmed by all of the components involved with being in academia; I think it’s important to remind myself from time to time how exciting it is to ask a question about why or how insects are doing something, especially in the field, and then figure out a way to answer it. I realized how awesome that is in this moment. 

MW: Before I started my graduate work, I volunteered for a research project with the US Fish and Wildlife Service’s Crazy Ant Strike Team, whose goal is to eradicate the invasive yellow crazy ant from a Pacific island. The island serves as important nesting habitat for ground-nesting seabirds, which the ants significantly disrupt. My crew’s goal was to test a few different control/eradication strategies so that the next team could implement the most effective one. The project has been very successful, leading to almost complete eradication of the ants and a significant recovery in seabird reproduction on this island! It feels incredible to have been involved in a conservation project that has made a positive and lasting impact!

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

KF: Yes, to both; I enjoy teaching (I have only had the opportunity to be a teaching assistant so far) and doing outreach. Depending on what I am teaching, I try to use relevant examples from social insects, especially bumblebees. I also really enjoy outreach. Depending on the group, I will introduce my specific research and why I do it or discuss the importance of pollinators and insects in general.

MW: Both as an undergraduate and graduate student researcher, I have been lucky to be part of entomology departments with strong focuses on outreach and I have been involved in many large-scale insect fairs throughout my academic career. Additionally, I have made it into many K-12 classrooms through these programs. I always try to incorporate my research into outreach events by introducing the basics of the colonial lifestyle and cooperative behavior of social insects. For more advanced audiences, I will also explain my experimental designs and findings.

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

KF: A question that I am interested in is how environmental context shapes social behaviour. A lot of super informative research about insect sociality has come out of laboratory studies. I think building on those findings to capture how variable they are across different populations and species is essential.

MW: If you read our paper, Fisher & West et al. 2018, then you already know. 🙂

IS: What research questions generate the biggest debate in social insect research at the moment?

MW: My general feeling is that a lot of debate surrounds honeybees – whether or not they are good/necessary for ecosystem functioning and whether their long history of being farmed makes them a useful model system for studying social insects.

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

KF: The last book I read was the Ministry of Utmost Happiness by Arundhati Roy. It is fiction, but it has powerful social and political commentaries about current events in India and globally. I enjoyed it, so I would recommend it to those who enjoy novels with strong social commentaries.

MW: The Jungle, by Upton Sinclair. It’s certainly not very upbeat, but I do think it is relevant to some social and economic issues that our world faces today.  It was a thought-provoking read.

 

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Kaleigh Fisher and family in Chiapas, Mexico

 

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

KF: Outside of science, I like to spend time with my family (hiking, gardening, cooking together).

MW: Hiking and baking. I like exploring the outdoors, mainly to observe wild animals in their natural environment, and working with my hands to make something tasty to share with others.

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

KF: Whenever I feel overwhelmed, I try to step away from everything for a moment, even if that means just going for a walk, so that I can get a better perspective on everything.

MW: I usually remind myself how lucky I am that my job brings me outdoors on a regular basis and keeps me intellectually engaged. I try to give myself some time to relax outside, to reflect and refresh my outlook on life.

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

KF: I would bring my partner because he is an expert field biologist and awesome human, and a notebook and a pen (to help organize my thoughts/ideas).

MW: Having previously lived on an uninhabited island to which I was able to bring pretty much everything I ever wanted, this is a tough question to answer. However, if I had to choose, I would bring a snorkel for exploring the coral reefs (and maybe making fishing a little easier), some sunblock, and someone with whom to share the experience. In my experience, you don’t need much more.

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

KF: I think my master’s thesis advisors have had the most significant influence on my scientific career. They have inspired me to be inherently curious about insects while simultaneously instilling in me the importance of doing science consciously and with a moral compass.

MW: Without Dr. Linda Rayor’s influence, I probably wouldn’t be studying social insects today. She was an incredible mentor, and her enthusiasm for and ability to communicate about her science caught my attention immediately. In addition to getting me interested in social insect behavior, she has inspired me to share my science with others around me.

 

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A bumblebee foraging experiment conducted by Kaleigh Fisher

 

 

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Ant abdomen painted by Mari West during a mark-recapture experiment

 

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

KF: Give yourself time to explore what kind of research you are passionate about. Being excited about the questions you are asking and the research you are doing is what it is all about.

MW: I would encourage them to spend some time working on different projects so that they can identify the questions that they are most excited about and learn about what kinds of experimental design work well for those questions. I would also encourage them to spend many hours watching their study organisms, for fun and inspiration.