Sex between species: what happens when invasive honey bees meet the locals?


A blog post highlighting the article by R. Gloag, K. Tan, Y. Wang, W. Song, W. Luo, G. Buchman, M. Beekman, B. P. Oldroyd in Insectes Sociaux

Written by Ros Gloag

Some social insects have proved to be adept invaders. Assisted by the international trade of the modern world, these species have spread far beyond the ocean and mountain barriers that once determined their distributions. In some cases, these range expansions have brought previously isolated sister species back into contact. What happens when such species try to mate?

We were interested in this question of interspecific mating in the case of two honey bees: the Western honey bee Apis mellifera and the Eastern honey (or hive) bee, Apis cerana. These species diverged from a common ancestor at least 6 million years ago, with A. mellifera native to Europe and Africa and A. cerana native to Asia and India. Western honey bees have of course since been transported, in association with agriculture, to every human-inhabited continent on earth. Eastern honey bees meanwhile, have been quietly expanding their range too in recent decades, invading both Papua New Guinea and Australia. Thus what were allopatric (or separate) ranges for millions of years have suddenly become partially sympatric.

A cerana

A swarm of Apis cerana hangs from a branch in its invasive range of Northern Australia, where the species has recently come into contact with A. mellifera. The newly-mated queen will be concealed at the centre of the swarm: but who did she mate with?

The possible outcomes of A. mellifera and A. cerana mating are varied. It may produce high-fitness hybrids, low-fitness hybrids or no viable offspring at all. In the case of honey bees, there is also a more unusual possibility; interspecific mating might cause queens to produce some female diploid offspring asexually via a process called thelytokous parthenogenesis. Thelytoky is not uncommon in Hymenoptera, though the mechanisms controlling it vary between species. In honey bees, it appears to have some genetic basis, but its unclear whether environmental factors – such as interspecific mating – also play a role in determining its incidence. Honey bee queens mate with twenty or more males during a short period early in their lives and store the sperm, so it is unlikely that naturally-mated queens will have mated exclusively with the wrong species. As such, any peculiar effects of interspecific mating could be easily obscured in populations where the two species co-occur.

We decided to perform an experiment to reveal the effects of interspecific mating on the offspring of A. mellifera and A. cerana. We performed reciprocal crosses via artificial insemination (inseminating queens of each species with the sperm of the other species) in China. Artificial insemination is a fairly standard beekeeping procedure for A. mellifera, but a much trickier business for the relatively diminutive A. cerana. Enough inseminated queens survived the procedure though to confirm that theytoky is not a consistent outcome of these matings. We detected only the odd few thelytokous eggs, from both queens and laying workers. Rather, our results confirmed that interspecific mating has fitness costs for both species: cross-inseminated A. mellifera queens produced only males or inviable hybrid females, while cross-inseminated A. cerana queens produced either males only or no eggs at all. Interestingly, A. cerana workers sometimes rebelled against their “wrongly-mated” queen and took control of reproduction themselves by laying unfertilized male-destined eggs.

Of course, understanding what happens if species mate is different to knowing whether they do mate. A previous study confirmed that A. mellifera will sometimes mate naturally with A. cerana males, but whether the reciprocal pairing ever occurs is unknown. We checked the sperm-storage organs of 17 A. cerana queens collected from Australia’s invasive population and failed to detect A. mellifera semen, despite the fact that we have observed A. mellifera males hanging about in areas where Australian A. cerana queens mate. Possibly A. cerana queens simply cannot survive interspecific matings with their larger sister species, which would be a particularly brutal and conclusive form of reproductive interference because its effects could not be diluted by multiple mating.

Wherever interspecific mating does occur between Western and Eastern honey bees, we can expect that natural selection will eventually intervene. After all, there are other honey bee species in the world that naturally coexist without incident, generally by having species-specific mating times and locations. A. mellifera and A. cerana are recent bedfellows, but given that interspecific mating in their case appears to have no redeeming features, selection should act to favour those queens and drones that succeed in keeping sex strictly within the species.

The queen is not dead!

A blog post highlighting the article by M. J. Ferreira-Caliman, J. S. Galaschi-Teixeira and F. S. do Nascimento in Insectes Sociaux

Written by Maria Juliana Ferreira-Caliman

A few species of stingless bees have fooled human observers. The queen, often seen on brood combs and exhibiting active egg laying, ceases her posture and hides herself between the food pots during an event known as reproductive diapause. Diapause is considered an adaptation that allows the queen (and colony’s) survival in adverse environmental conditions. This event is mostly common in temperate zones, but it also occurs in the tropics as an adaptive response to diminishing resources in the cold and dry season.

Reproductive diapause is common among queens in the stingless bee genus Plebeia, occurring as an obligatory condition in some species. Reports on the occurrence of reproductive diapause in other stingless bee genera in Brazil are scarce. In our study, we described for the first time the occurrence of reproductive diapause in Melipona marginata in Southeast region of Brazil, comparing this event with events observed in South Brazil by Borges and Blochtein (2006) in Melipona obscurior, a closely related species. In the study described here, we compared the photoperiod and temperature in both localities to understand the factors that trigger the reproductive diapause in eusocial bees. In addition, we compared the queen’s chemical profile before and during reproductive diapause to verify the occurrence of chemical changes in the signaling of fertility.


Fig1. A Melipona marginata queen in regular egg laying activity. Photo: M. J. Ferreira-Caliman.

We observed that Melipona marginata queens gradually declined the frequency of oviposition in early May, and in the cold and dry months (to May from July) they ceased egg laying completely. Five out of six colonies we observed entered the reproductive diapause, suggesting that this event is facultative in Melipona bees and that this variation is determined by internal factors of the nests, such as the ratio of adults to brood and food stores.

The environmental factors involved in reproductive diapause are commonly associated with photoperiod and temperature (Derlinger, 2002). The photoperiod and temperature seem to be the triggering factor of reproductive diapause in M. marginata in Southeast Brazil, as well as Melipona obscurior in South Brazil. In these two species, the reproductive diapause period coincided with the months of shorter day length and low temperatures, occurring between the months of March and August, suggesting that the reproductive diapause is a mechanism used by Melipona bees to overcome the diminishing resources in the cold and dry season.

The workers did not stop their activities and all behaviors related to colony maintenance were performed, such as queen feeding and food collection (although cell construction was stopped). However, the queens showed conspicuous behaviors. They walked through the entire colony, including in the food pots. The queens’ enlarged abdomen (a typical morphological aspect of post-mating stingless bee queens), did not disappear during reproductive diapause, but we observed that the posterior portion of abdomen decreased, suggesting oocytes were resorbed.

So, faced with the behavioral and morphological changes, why were queens not replaced by gynes when they stopped oviposition? The answer can be related to the chemical communication between the castes, which allows cohesion in the social insect colonies. The chemical analysis of Melipona marginata queens showed that the cuticular hydrocarbons profile does not change qualitatively during the diapause phase. Probably, this may explain why the workers have not killed the queens in this period, and why the workers did not lay eggs, a common occurrence in Meliponini colonies. Chemical and behavioral evidence suggest that two specific groups of hydrocarbons, the methyl-branched alkanes and alkenes, may act as fertility signals. The cuticular profiles of Melipona marginata before and during reproductive diapause had a greater and similar amount of hentriacontene isomers (alkenes). These results reinforce the idea that the chemical signals are crucial to maintaining the organization in insect societies, even in periods of adversity


Borges FVB, Blochtein B (2006) Variação sazonal das condições internas de colônias de Melipona marginata obscurior Moure, no Rio Grande do Sul, Brasil. Rev Bras Zool 23:711-715

Denlinger DL (2002) Regulation of diapause. Annu Rev Entomol 47:93-122






Interview with a social insect scientist: Neil Tsutsui


Neil Tsutsui in the field. Photo: Roberto Keller-Pérez

IS: Who are you and what do you do?

NT: I’m Neil Tsutsui, Professor of Arthropod Behavior at UC Berkeley, in the Department of Environmental Science, Policy and Management.

IS: How did you end up researching social insects?

NT: Maybe a mix of fate and luck? As a child, the first thing I ever said that I wanted to be when I grew up was an entomologist, so I might have a genetic predisposition for it. My route was circuitous, though. I majored in Marine Biology as an undergrad, then started off in graduate school as a cell biologist, studying the Golgi apparatus. After deciding that I wanted to spend my career studying organisms rather than organelles, I jumped over to the lab of an evolutionary ecologist (Ted Case). There, I started working on a project using microsatellites to quantify gene flow across a hybrid zone of whiptail lizards. Andy Suarez was a graduate student in the same lab, and he was studying the impact of invasive Argentine ants on native ants and horned lizards. David Holway joined as a post-doc soon afterward. Since we were always chatting about Argentine ants, and they had colonies in the lab, it seemed like a good idea for me to do something with them, as well. Once I started seeing the genetic data from Californian populations of Argentine ants, it was obvious that something interesting was going on – they had very, very little genetic variation across long distances. Quite opposite to what I was seeing in my lizard data. I started spending more and more time on the Argentine ant project, and have continued with them ever since. I never finished the lizard project.

IS: What is your favourite social insect and why?

NT: Argentine ants have been like Karl von Frisch’s “magic well” for me, so I have great fondness for them. I’m becoming increasingly fascinated with Polyergus, though.

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

NT: Hard to say. Seeing the first population genetic data from native and introduced Argentine ants is up there: I was pretty surprised by the extreme differences in genetic diversity and spatial genetic structure. Later, our experimental confirmation of colony recognition cues was also fun – it was amazing to see Argentine ant nestmates attack each other when we altered their colony odors with synthetic hydrocarbons.

IS: If teaching is part of your work, what courses do you teach? Has your work on social insects helped to shape your teaching?

NT: I mainly teach Insect Behavior and senior seminars for undergraduates, plus the occasional graduate seminar on chemical ecology or other specialized topics. Social insect examples are very prominently on display throughout my Insect Behavior course.

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

NT: Just finished “The Left Hand of Darkness,” by Ursula Le Guin. Yes, recommended – a nice short read, but quite interesting.

IS: Did any one book have a major influence in shaping your career? What was the book and how did it affect you?

NT: I don’t think that there was a single book, but a cumulative influence of National Geographic and Natural History magazines when younger, books by Stephen Jay Gould and Richard Dawkins in high school, and, of course, E.O. Wilson later.

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

NT: Lots of different things, but none of them with any high level of proficiency: urban farming, birding, saltwater aquarium-keeping, parenting.

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

NT: Well, things are often tough in academia. Eventually you accept that sometimes you’ll be in over your head, it’ll just be too much, and you’ll fail. Reviews won’t get done, you’ll miss meetings, classes will go badly, etc. Over time, I’ve learned to say “no” to avoid having commitments pile up, and I’ve grown accustomed to just grinding through the tough patches and not letting the failures upset me too much.

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

NT: You mean that I’m stuck on the island forever? Then it’s gotta be something along the lines of solar still, fishing gear, and magnesium-flint firestarter.

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

NT: Probably my colleagues Andy Suarez and David Holway. Let’s get together for a reunion tour, guys!

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

NT: Well, there are lots of different ways of doing science, so the same formula won’t work for everyone. But I’d say one thing is to make sure that you’re always learning about things outside of your main field of interest. Even if you end up becoming a hyper-specialist in your own research, you’ll benefit from viewing the world through a broader lens.


Interview with a social insect scientist: Alex Wild


IS: Who are you and what do you do?

AW: I am Alex Wild, Curator of Entomology at The University of Texas at Austin. I also run a small insect photography business. I suppose most people know me for the photos.

IS: How did you end up researching social insects?

AW: I wish I had a logical answer for why I’m so taken by social insects. But I don’t. I started early in life, so early that the infatuation seems to have been an inchoate, primordial fixation from a mis-wiring of my brain stem. I was collecting carpenter ants at five, for example, and many of my early childhood drawings depict crude tunnels of ant nests. I didn’t- and still don’t- know why I like social insects, though I can come up with all manner of post-hoc rationalizations.

True story. At age 8 an older cousin I did not know well inquired about my interests, as way of introductory small talk. I think she was expecting some standard answer like “Hockey” or “Video Games” or “Ice Cream” or whatever the kids liked those days. I announced, instead, “I like colony insects!”.

In college (Bowdoin), my ecology professor Nat Wheelwright explained me that one could actually have a career studying ants. I had no idea! Nat started me down a path that eventually led to taxonomy.

IS: What is your favourite social insect and why?


A turtle ant- Cephalotes multispinosus. Photo credit: Katja Shulz/Flickr

AW: Turtle ants! Or maybe paper wasps? Hard to say. I love Iridomyrmex, in Australia, quietly running the continent while everyone else is distracted by the giant bull ants.

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

AW: I discovered a new genus of ant on Google once, in the early days of the internet. I didn’t do anything with it at the time. A year later, I stopped to watch the sunset in the middle of the Paraguayan Chaco and accidentally happened across a living colony of the same mystery ant. That was exciting- I recognized it right away. I worked with Fabiana Cuezzo to describe it formally as Gracilidris.

IS: If teaching is part of your work, what courses do you teach? Has your work on social insects helped to shape your teaching?

 AW: I teach Introductory Entomology at UT-Austin. It’s a challenging environment for a bug guy, as UT has no Entomology Department, so my little course is the only entomology most students get and few students have an entomological background. Of course, we use a lot of social insect examples in the lectures and labs.

I taught beekeeping at the University of Illinois for a couple years. It was a tremendous class. Universities would do well to invest more in small courses that combine hands-on activities with general biological theory. We covered both honey extraction and the debates over kin selection.

Mostly, though, I teach photography. Social insects occupy a special place for the insect photographer. Normally, the aesthetic challenge is to make alien-looking species appear relatable to the naïve human audience. Social insects anthropomorphize themselves. It’s much easier to take a compelling photograph of an ant- a photograph that non-biologists can relate to- than of a non-social beetle or fly.

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

AW: “Lab Girl” by Hope Jahren. Recommend!

IS: Did any one book have a major influence in shaping your career? What was the book and how did it affect you?

AW: I often return to the concepts in Maynard Smith & Szathmary’s “Major Transitions in Evolution.”

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

AW: I kind of have my hobby for job. So I alternate between sleep, kid care, and hobby.

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

AW: I find point-mounting therapeutic. Doesn’t everyone? But, emotionally, I rely a great deal on my wife and two young children. Having kids has rather mellowed my outlook.

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

AW: Islands can be pretty depauperate. I’m more of a lowland forest guy. Am I allowed a boat with oars?

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

AW: My scientific instincts are moulded on those of my Ph.D. advisor, Phil Ward. But I’d be lying if I didn’t say I am most influenced by my parents, neither of whom are scientists themselves but they knew how to play the long game by encouraging an inquisitive, social-insect obsessed young mind.

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

AW: Normally I’d advise not worrying too much about the particulars of how one enters science- there are many paths to get where you’d like to go, as well as many destinations you may not have thought of. At least, that’s how it’s been in recent decades.

But today? We live in a perilous time, and retreating inward to the lab is capitulation. I advise connecting with local universities, museums, non-profits, and other science organizations to engage aggressively in outreach. You’ll make connections that may prove valuable later in your career, and you’ll help ensure that basic science survives the current mess.



Interview with a social insect scientist: Jennifer Fewell

j-fewellIS: Who are you and what do you do?

JF: I am Jennifer Fewell. I study the organization, evolution, and ecology of insect societies, primarily focusing on ants and honey bees.

IS: How did you end up researching social insects?

JF: I went into grad school to study the relationships between food and social organization (probably because I like to be social and to eat). My original goal was to study canids, but that became too logistically complicated. I had switched to birds as a focal taxon, but found that birds seem to be much smarter than I am. By my second year, I had switched advisors to the wonderful Mike Breed. One day he took me out to a local park that was covered in harvester ant nests (Pogonomyrmex occidentalis). We watched them for a while; then he gave me a paper by Bert Hoelldobler to read and told me to go home and think about them. The next day I had my dissertation project sketched out and I have never looked back. Social insects are so much more elegant and fascinating in their social organization than any other group.

IS: What is your favourite social insect and why?


A newly-emerged honey bee. Photo credit: Jon BeesinFrance/Flickr

JF: I can’t answer that. My favorites to watch have been ant queens and solitary bees. For pure attractiveness, I’d have to pick between a harvester ant, a leafcutter ant and a newly emerged honey bee. Honey bees are definitely the cutest, but harvester ants have a sleek but striated look to them that in my mind cannot be matched.

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

JF: My favorite experimental result was showing that normally solitary nest-founding ant queens show an emergent division of labor when forced to be solitary. We repeated and verified the finding in solitary bees. This first experiment tested a then new model of how social interactions affect individual phenotype in the context of division of labor and task organization. It set the stage for most of the work I’ve done since. The original study had fantastic results, but the idea was not well accepted at first. I argue that is okay, because it required a change in how we have to think about social phenotypes and selection. The doubt expressed by the scientific community at the time forced my lab to explore the paradigm in other species, and to test it more rigorously. So, it is a story of initial frustration in how science is discussed and received, but I think with a happy ending…although nothing in science does or should actually have an ending.

IS: If teaching is part of your work, what courses do you teach? Has your work on social insects helped to shape your teaching?

JF: I teach animal behaviour and sociobiology. One of the things I like about teaching the courses is that they force me to be less insect-centric in my thinking about social evolution, and to be more aware of the diversity of social forms out there. So, my teaching has helped to shape my research as much as my research has helped to shape my teaching.

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

JF: Ah no – I read a lot of science fiction for fun, and so don’t have a very worthy suggestion. I am currently also reading Jim Costa’s “The Other Insect Societies”, which I would recommend any social insect student owning – to remind us that ants, bees, wasps (and termites) do not represent the whole social insect world.

IS: Did any one book have a major influence in shaping your career? What was the book and how did it affect you?

JF: The book that most influenced me as an undergrad was Wilson’s book, “Sociobiology: The New Synthesis”. I don’t want to say how far back that was, but I vividly remember reading the book in my advanced animal behaviour class, and I felt that I’d found a new world to explore and a new way to explore it. Wow.

I suppose that now the world has incorporated and moved forward from that text. For the incoming social insect student, Hoelldobler and Wilson’s “The Superorganism” is wonderful. Way back, Hoelldobler’s work set me down my research path, and this book may do the same for some other student.

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

JF: I ride horses.

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

JF: I fuss out and complain a lot to my poor husband. Then I stay up late and get things done.

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

 JF: As a biologist, I would have to say that depends entirely on the ecology of the island.

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

JF: Mike Breed, my grad advisor (as already mentioned) got me started on my research path, and has been a steadying and encouraging presence ever since. My current work traces directly back to the influence of Rob Page, with whom I worked on honey bee division of labor, and whose ideas still shape much of what I do. But my decision to make animal behavior a career started when I took a course in college with Bill Dilger, an ornithologist and ethologist. Bill was the consummate natural historian. We would go for walks in the woods, and Bill would point out songs and behaviors well beyond what I would see…and then explain what was going on around us. I began thinking of the animals around us as a city of arguing, cajoling and romancing individuals, all living interesting lives.

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

JF: Work at it, and learn to design experiments correctly – models and theory are important, but the experiment done well gives you an answer.

Usurping the Queen

Highlighting the article written by T. Saga, M. Kanai, M. Shimada and Y. Okada in Insectes Sociaux

Written by Insectes Sociaux Editor in Chief, Michael Breed

In this issue of Insectes Sociaux Saga et al (2017) present a fascinating long-term study of nest usurpation and social parasitism in Vespula wasps. Reproduction based on usurpation is relatively rare in vespine wasps and outcomes are often only anecdotally reported. Vespula flaviceps and V. shidai can each have colonies with normal reproductive strategies, but some queens in each species usurp nests of either their own species (intraspecific usurpation) or the other species (interspecific usurpation).   Saga et al (2017) focus on interspecific usurpations. In an eight-year study they documented ten cases of interspecific usurpation. In nine of these the resulting colony had a V. shidai queen and in the remaining one the queen was V. flaviceps. The workers in these colonies were predominantly V. flaviceps, but the gynes and males produced were nearly all V. shidai. This suggests that V. shidai has a selective advantage in this relationship and raises the interesting question of whether facultative social parasitism can provide a route to the evolution of obligate parasites.


Vespula flaviceps. Photo by harum.koh from Kobe city, Japan via Wikimedia Commons

Facultative social parasitism differs from obligate relationships in that facultative usurpers exploit the nest as a resource but can also produce their own workers. In facultative parasitic wasps the usurped colony may ultimately contain a blend of host and parasite workers or may consist of only parasite workers. Obligately parasitic social wasps, on the other hand, must always exploit the workers of the host species, as they only produce sexuals, not their own workers.

Based on the observations that V. flaviceps nests usurped by V. shidai produced sexuals of V. shidai, these facultative social parasites present provocative questions in understanding animals’ reproductive choices. Among the social wasps, three types of social parasitism are known: intraspecific facultative nest usurpation, interspecific facultative usurpation, and obligate social parasitism (e.g. sulcopolistes species group of Polistes (Cervo 2006), Dolichovespula arctica (= adulterina)) but whether the former two are evolutionary stops on the road to obligate social parasitism are unknown.

Facultative social parasites seem to make a reproductive choice to usurp a nest, rather than establish one on their own. The choice of host species usually follows Emery’s rule- that a socially parasitic species exploits its taxonomic sister species. However, this is not always true, and relatively closely related species, with similar social behavior and communication, are pre-adapted to exploit each other by virtue of possessing the “keys to the kingdom”, a repeated theme in the discussion of the evolution of social parasitism (Breed 2016). Thus social parasites often belong to the same genus as their hosts.

But little is known about the genetics that underlies social parasitism in wasps, and possibly differing reproductive strategies reflect underlying genetic divergences within populations. Within-species sympatric divergence—Emery’s rule strictly applied- is very rare and seems an unlikely route to obligate parasitism. Facultative social parasitism can be an evolutionarily stable strategy, rather than a step towards obligate parasitism (Lowe 2002). However, in relationships such as the one described by Saga et al (2017) one species could gain the upper hand in competition among free-standing nests while the other could evolve superior parasitic strategies. In that case the outcome could be the evolution of obligate parasitism by the species that is the superior parasite but inferior independent competitor.

Vespula flaviceps and V. shidai are already distinct species. Saga et al (2017) fill out a more complete picture of the outcomes of facultative social parasitism among similar species; their work has high value in adding to our understanding of these intriguing relationships.


Breed M D (2016) Social parasitism: the keys to the kingdom. Insect. Soc. 63:3–4
DOI 10.1007/s00040-015-0458-7

Cervo R (2006) Polistes wasps and their social parasites: an overview. Ann. Zool. Fennici 43: 531–549

Lowe RM, Ward SA, Crozier RH (2002) The evolution of parasites from their hosts: intra- and interspecific parasitism and Emery’s rule. Proc R Soc B 269:1301–1305

Saga T, Kanai M, Shimada M, Okada Y (2017) Mutual intra- and interspecific social parasitism between parapatric sister species of Vespula wasps. Insect. Soc.
 DOI 10.1007/s00040-016-0519-6

An ant is taking over sacred church forests in Ethiopia


Fighting Lepisota ants.

A blog post highlighting the article by D. M. Sorger, W. Booth, A. Wassie Eshete, M. Lowman and M. W. Moffett in Insectes Sociaux

Written by Magdalena Sorger

When I was asked to join a team to conduct a biodiversity survey of ancient church forests in Ethiopia, I was pretty excited. There were plant experts, beetle experts, fly experts and two ant experts – myself and Mark Moffett. However, our first big ant discovery was unexpected and frankly a bit alarming (yet I won’t deny that it was also exciting): We found a single ant species – everywhere. Well, almost everywhere.

The species, later identified as Lepisiota canescens, exhibited characteristics common in invasive species such as Argentine ants (Linepithema humile) including supercolony formation. Argentine ants are worldwide invasives and pose a significant threat to local biodiversity wherever they go. If the ant we found in Ethiopia was capable of anything like Argentine ants are capable of, then that was a very good reason to worry – and to pay attention.


Magdalena on the ant hunt. Photo credit: Mark Moffett

Church forests surround Orthodox churches some of which are over 1,500 years old. The forests range in size from only a few hectares to more than 400 ha and are considered relictual oases within largely barren land and agricultural fields. We discovered Lepisiota canescens to be numerous, first in the most degraded church forest (Zhara Church forest = 8 ha) but then also around the church forest, in agricultural fields, along the paved road and in a more urban setting in the city of Bahir Dar. The species exhibited many characteristics reminiscent of invasive species, such as ecological dominance, general nesting and diet, and, most interestingly supercolony-formation.

Supercolonies are colonies that extend beyond just a single nest. The colony spans many nests and can sometimes cover many thousands of kilometers (see Argentine ants for the most famous example). The strongest basis for describing a large colony as a supercolony is its capacity to expand its range without constraints.

In this study we conducted behavioral experiments to show the extent of supercolonies. And we found several supercolonies, the largest one spanning a mighty 38 km.  We also conducted molecular analyses to test whether 1) the species showed the genetic signature of an invasive species and 2) if supercolonies corresponded to genetic identity (i.e. more closely related ants were part of the same supercolony). And – surprisingly – we found that the species shows the genetic signature of a native species and that genetic identity does not correspond to supercolony identity.

These results are significant for a two main reasons: 1) supercolony formation in ants is a rare trait, there are only about 20 species with documented supercolonies, even fewer with really large supercolonies, and 2) other species in the Lepisiota genus have recently made headlines as worrisome invasive species, one in Kruger National Park and another one was reason for shutting down Darwin port (Australia) for several days.


Lepisota killing a termite.

The species we found in Ethiopia may have a high potential of becoming a (globally) invasive species, especially with tourism to this region in Ethiopia on the rise. It is important to have a record of what a species does in its native habitat because rarely do we know anything about the biology of a species BEFORE it becomes invasive.

We believe this species, while native to the general region, is moving into disturbed habitat locally like the degraded forest, feeding on honeydew excreted by insects that occur on a locally invasive plant which only appeared with the construction of the road and other urban structures. Maybe a native species invading disturbed habitat locally is a first step before it “goes international” and it’s worth keeping an eye on.

Trouble at the farm: a new case of thief ants stealing the gardens of fungus-growing ants

A blog post highlighting the article written by D.C. Cardoso, M.P. Cristiano, C.B. da Costa-Milanez and  J. Heinze in Insectes Sociaux

Written by Aniek Ivens

Sometimes a chance encounter leads to a new scientific discovery. Let me tell you the story of four biologists in Brazil who were looking for fungus-growing ants and then discovered that these ants’ fungus gardens got stolen by other ants: thief ants. This discovery is more than just a fun fact; below you’ll find how it may contribute to a better understanding of the farming practices of ants, which are cases of mutualism and how these mutualisms persist despite the threat of parasites.

Our historical transition from a hunter-gatherer to a farming-based lifestyle contributed significantly to our success as a species.

We humans weren’t the only beneficiaries when we transitioned to farming. The crops and animals that we keep and farm also benefited from this interaction. For example, in some countries there are at the moment more pigs than humans. It is hard to imagine that such vast numbers of pigs could be maintained in the wild without human assistance4. These reciprocally beneficial cooperative relationships between the farmers and the farmed species are called ‘mutualisms.’

Given the mutual benefits to farmers and the species they farm, it is not surprising that we are not the only organisms that practice agriculture or husbandry. Nature provides many examples of such non-human farming: there are ants that farm aphids as we do cattle, damselfish that grow little gardens of algae in the sea, and even amoebae that farm bacteria. Perhaps the most frequently grown crop out there is fungus: we find ‘mushroom growers’ among termites, beetles, sloths, snails, and, of course, ants.


Figure 1: A worker of fungus-growing ant Trachymyrmex intermedius carries a leaf to the nest as substrate for its fungus. Photo: Alex Wild (

Fungus-growing ants are sophisticated farmers. They build subterranean nests in which they grow gardens of fungi, for food. To grow the fungus they bring in substrate from outside the nest, often flowers or cut leaves (Fig. 1). They also maintain the garden by applying their excrement as manure and planting new tufts of fungus.

The ants and fungi together form thriving little communities from which they both profit. Unfortunately, their success also puts them at risk: any thriving mutualism will attract parasites that reap the benefits without paying the costs. Yet, many mutualisms persist and how they defend themselves against these parasites is a major question in biology. Studying the interactions between mutualists and their parasites can shed light on this question.

It is no surprise that the ants’ fungus-garden risks parasite invasion. We’ve long known that ants need to actively weed out and even apply pesticide to parasitic fungi, which try to profit from the ants’ care without providing food. In recent years, it has become clear that the fungus-gardens also risk ‘agro-predation’, in which other ants come in and steal the entire garden5. This is of course a major loss – imagine you have carefully planted a patch of strawberries and once they are ripe, somebody comes in and steals all of them!

In the study highlighted here, the biologists discovered by chance that this is exactly what happens to Mycetophylax (My) fungus-growing ants. The biologists set out to collect some colonies of My ants from sand dunes near Ilhéus, Brazil. However, in one case, they found that the fungus-garden was inhabited by a different ant, Megalomyrmex incisus (Me) (Fig. 2). No Mycetophylax ants were in sight. Knowing that other Me can be agro-predators5, or ‘thief ants’, they hypothesized that this nest indeed had been usurped by the Me ants and brought it to the lab to test this hypothesis.


Figure 2: Thief ant Megalomyrmex incises seen from the front (‘frontal view’, a) and its left side (‘lateral view’, b). Photo: Cardoso et al. 2016

The researchers first confirmed that the found Me ants were parasitic ants, by testing whether these ants were able to rear the fungus garden themselves. As it turns out, the Me ants could not. Although they ate the fungus, they did not provide the fungus with substrate and did not weed it. As a result, the fungus died within three weeks.

Next, the scientists gave the thief Me ants the opportunity to steal a fungus, by providing the colony with a piece of fungus garden including about 20 workers of its original farmers, the My ants. Turns out that raiding a fungus garden is indeed what the Me ants are very good at: within an hour, they had taken possession of the garden and expelled all My ants by employing an arsenal of aggressive weaponry. The thieves bite, sting and pull the My ants (see video below). Presumably in response to the venom the Me ants produce6, the My ants mostly play dead – and the thief ants just carry them off their garden.

Why didn’t the My ants, the mutualists, evolve to protect their garden better? The reason is probably the same as the reason why nobody observed this case of agro-predation before: the chance of these Me ants encountering a My colony is just extremely low. This is because Me ants are rare and the habitats of these two different types of ants hardly overlap. Evolution is only able to shape better defenses when an attack happens often enough.

Even though it only happens rarely, this case of agro-predation by Me ants can still be very valuable for science. Combined with other known cases of garden-stealing by Me ants5,7,8, it will allow us to study the strategies of parasites – and their victims’ defenses against them – in more detail. Ultimately this will contribute to a better understanding of the fragile balance between mutualists and parasites and how best to protect mutualist crops (and maybe even our own) from being stolen by other species.



  1. Cardoso, D. C., Cristiano, M. P., Costa-Milanez, C. B. da & Heinze, J. Agro-predation by Megalomyrmex ants on Mycetophylax fungus-growing ants. Insectes Sociaux 63, 483–486 (2016).
  2. Larsen, C. S. Biological changes in human populations with agriculture. Annu. Rev. Anthropol. 24, 185–213 (1995).
  3. Diamond, J. Evolution, consequences and future of plant and animal domestication. Nature 418, 700–707 (2002).
  4. Aanen, D. K. As you weed, so shall you reap: on the origin of algaculture in damselfish. BMC Biol. 8, 81 (2010).
  5. Adams, R. M. M., Norden, B., Mueller, U. G. & Schultz, T. R. Agro-predation: usurpation of attine fungus gardens by Megalomyrmex ants. Naturwissenschaften 87, 549–554 (2000).
  6. Adams, R. M. M., Jones, T. H., Longino, J. T., Weatherford, R. G. & Mueller, U. G. Alkaloid venom weaponry of three Megalomyrmex thief ants and the behavioral response of Cyphomyrmex costatus host ants. J. Chem. Ecol. 41, 373–385 (2015).
  7. Adams, R. M. M. et al. Chemically armed mercenary ants protect fungus-farming societies. Proc. Natl. Acad. Sci. 110, 15752–15757 (2013).
  8. Adams, R. M. M., Shah, K., Antonov, L. D. & Mueller, U. G. Fitness consequences of nest infiltration by the mutualist-exploiter Megalomyrmex adamsae. Ecol. Entomol. 37, 453–462 (2012).


About the author:
Aniek Ivens is a postdoctoral fellow in the “ant lab” (Laboratory of Social Evolution and Behavior) at The Rockefeller University, New York, NY, USA. Check out her website for more information on her research on subterranean ant-aphid farming. You can also follow and tweet to her at Twitter @AniekIvens.



Decisive dancing in honey bees

A blog post highlighting the article written by J. C. Makinson, T. M. Schaerf, A. Rattanawannee, B. P. Oldroyd and M. Beekman in Insectes Sociaux


Written by Rachael Bonoan

Decision making is hard. Decision making in a group is even harder. The vultures from Disney’s The Jungle Book come to mind. What we gonna do? I don’t know, whatcha wanna do? And so it goes.

Honey bees are an example of a superorganism. Not only do they work together to run their large and complex societies, they also work together to decide on a new home.

When honey bees decide it’s getting too cozy in their hive, half of the bees will leave with the old queen and swarm to an intermediate location. The remaining bees will stay home with a newly raised queen.


Rachael Bonoan with a swarm outside a hive entrance. Photo: Salvatore Daddario

While the bees are clustered in their swarm, special members of the colony, aptly named scout bees, check out possible new homes in the area and report back to each other via dancing. In their dances, the scout bees encode the location and quality of each potential new home. Eventually, the scout bees decide on a new home and, after a consensus is reached, the swarm takes off. Before the swarm takes off, it is vital that all the bees agree on where they are going. In European honey bees, we know a lot about this process. Until recently however, we didn’t know how Asian honey bees (Apis dorsata) make this important decision.

Unlike European honey bees, Asian honey bees nest out in the open and their colony’s population size is not constrained by a nest cavity. As such, Asian honey bees tend to swarm to find a home with more food rather than to find a home with more room for all those bees.


Asian honey bees nesting on a tree branch. Photo: Wikimedia Commons

Asian honey bees are much quicker at making decisions about a new home than European honey bees (hours vs. days respectively). How do Asian honey bees make a group decision so quickly? Recently, James C. Makinson and colleagues asked the question, how does group decision-making in Asian honey bees differ from group decision-making in European honey bees?


Swarm board and video camera set up. Photo: Makinson et al. 2014.

To investigate this question, the research team first created Asian honey bee swarms which were released onto a swarm board. Equipped with a video camera, the researchers filmed the scout bees as they searched for new home sites and made their decision. The researchers measured dance and flight activity, and to get an idea of individual behavior, they labeled the scout bees with colored paint.

Like European honey bees, individual Asian honey bee scouts take flight in between dances, and before lift-off, dances converge in a similar direction. Also, in both species, the duration of a scout’s dance is directly related to the quality of the new home site.

Unlike European honey bees however, Asian honey bee scouts do not exhibit a phenomenon called dance decay when narrowing down their choice. In European honey bees, a scout visits a potential new home multiple times and each time, the duration of her dance shortens. Another scout follows the dancer’s directions to check out the site herself. This recruited scout will also visit the site multiple times; she too will shorten the duration of her dance with each visit. Since scouts do longer dances for more favorable homes from the start, scouts dancing for higher quality homes will continue dancing even after dances for lower quality homes have ceased. Eventually, dance decay results in only dances for the most favorable home site. This is when the bees take off.

Asian honey bees use a different means of coming to a consensus. Makinson and colleagues found that scouts dancing for a “non-chosen” location change their dance direction after observing the dance of a “chosen” location. Thus, Asian honey bee scouts switch their dances—or change their minds—without visiting the potential new home themselves. These “switchers” simply trust what the other scout bees are telling them. This is likely how Asian honey bees make their decision so much faster than European honey bees. It also suggests that checking out the site themselves isn’t as important to Asian honey bees as it is to European honey bees. Based on their nesting behavior, this makes sense. Since European honey bees nest in cavities, the bees check out the cavity to make sure it’s the right shape, size, height, etc. Since Asian honey bees nest in the open, they have less factors to debate about when making their decision.

It seems that Asian honey bees are efficient at group decision-making because they pay attention to only the pertinent information. They don’t let irrelevant factors (in their case, shape, size, height, etc. of the home site) get in the way. They stay focused on the specific task at hand: find a new home.


Makinson JC, Schaerf TM, Rattanawanne A, Oldroyd BP, Beekeman M. 2016. How does a swarm of the gian Asian honeybee Apis dorsata reach consensus? A study of the invidual behavior of scout bees. Insectes Sociaux 63: 395-406.

Makinson JC, Schaerf TM, Rattanawanne A, Oldroyd BP, Beekeman M. 2014. Consensus building in giant Asian honeybee, Apis dorsata, swarms on the move. Animal Behavior 93: 191-199.

Seeley TD, Visscher KP, Passino KM. 2006. Group decision making in honey bee swarms. American Scientist 94: 220-229.


About the author:
Rachael Bonoan
is a PhD student at Tufts University in Medford, Massachusetts, U.S.A. You can tweet to her at @RachaelEBee or check out her website: where she writes her own blog.

The paraphyly controversy

Highlighting the articles written by Ward et al. and  Seifert et al. in Insectes Sociaux

Written by Insectes Sociaux Editor in Chief, Michael Breed

Should we change a commonly used and widely understood name when bringing classification into alignment with phylogeny? This is not a new question; it has plagued generations of systematists (e.g., Michener 1964). The Linnean system of classifying and naming organisms is a foundational tool in biological sciences. Yet not all scientists agree about how and when information about phylogeny should be embedded into classification. A particularly sticky point comes when well-accepted names for organisms conflict with newly understood phylogenetic information. The second of a pair of commentaries dealing with phylogeny, classification and scientific names appears in this month’s issue of Insectes Sociaux (Ward et al. 2016; Seifert et al. 2016).

Particularly vexsome in the social insect world have been classifications involving social parasites. Are there clear synapomorphies-traits that distinguish the social parasite from its hosts? Alternatively, is each socially parasitic species within a clade an evolutionary offshoot from shared ancestors with its host species? Or is it a distinct clade within a clade? Are parasitic characteristics, which often involve loss of foraging morphology, arrived at by convergence? The answers to these questions often affect a species’ name, in particular its placement in a genus.

The two commentaries address the question of whether, when new data reveals that genera are paraphyletic, should their naming reflect the current phylogeny. In ants, there are several examples of groups of parasitic species for which new data has caused placement within a host genus, when previously the parasites had generic status. The renaming of species has been controversial and lies at the core of the disagreement between the two groups of authors.

The much-studied relationship between bumblebees, Bombus, and their social parasites, Psithyrus, exemplifies the fascinating difficulties posed by social parasites. Psithyrus differ substantially in morphology and behavior from their hosts so much that the early literature (e.g., Plath 1922) considers Psithyrus as a distinct genus. At points in the past, Psithyrus species have also been argued to have evolved pairwise from their hosts. The contemporary understanding (Cameron et al. 2007) is that Psithyrus comprises a single clade within Bombus, and it is recognized as a subgenus. Thus, in this case the name reflects the currently supported phylogenetic hypothesis, and most bee biologists have come to accept Psithyrus as a part of Bombus.

The readers of Insectes Sociaux are very much affected by controversies over naming social parasites, as many non- taxonomic studies focus on the behavior, ecology and evolution of these insects. It is possible that a student, new to the field, might find that changed names make it difficult to connect older literature with newer work. Importantly, though, to the extent that the naming system is a hypothesis about evolutionary relationships, names that do not embody current phylogenetic knowledge could also mislead a student about evolution. Knowing that new hypotheses about phylogeny will appear in the future and, perhaps affect names, adds tension to the situation.

Name changes make things inconvenient and awkward at times; in my own work on halictid bees I have seen that the shifts between Dialictus and Lasioglossum as the genus name for the same bee¹ have been confusing to biologists outside the inner circle of halictid biologists. On the other hand, the removal of the ant genus Paraponera from the tribe Ectatommini as well as from the subfamily Ponerinae greatly informed my thinking about the evolution of Paraponera behavior, a definite positive outcome of the current reworking of ant systematics.

Why should a journal publish commentaries on an issue like this? The role of scientific journals is to document an extended conversation about theory, hypotheses and facts. My view is that it is far better for scientists to have open, and one would hope civil exchanges about controversial topics. This ensures scientific progress and helps workers outside the immediate field understand seeming contradictions. My personal agreement, or disagreement, with the point of view of either Ward et al. (2016) or Seifert et al. (2016) is much less important than the discussion of the issue within the scientific community. Additionally, one constant concern of journal editors is that the peer review system can be used to suppress work in ways that are difficult to ferret out in the editorial process. Having the conversation in a transparent way should help to advance science and maintain the integrity of editorial processes.

¹ Thus, Lasioglussum zephyrum = Dialictus zephyrus, because the Latin ending of the species epithet changes to match the ending of the genus name. I think this name mismatch inhibits non-specialists from accessing the comparative value of the literature on halictid bee behavior, but the present usage, L. zephyrum, is well justified on systematic grounds. This is a different naming issue than the question about social parasites, but it has many of the same potential outcomes and conflicts in terms of utility.


Cameron SA, Hines HM, Williams PH (2007) A comprehensive phylogeny of the bumble bees (Bombus). Biol J Linn Soc 91:161–188

Michener CD (1964) The possible use of uninominal nomenclature to increase the stability of names in biology. Syst Zool 13:182–190 Plath OE (1922) Notes on Psithyrus, with records of two new American hosts. Biol Bull 43:23–44

Seifert B, Buschinger A, Aldawood A, Antonova V, Bharti H, Borowiec L, Dekoninck W, Dubovikoff D, Espadaler X, Flegr J, Georgiadis C, Heinze J, Neumeyer R, Ødegaard F, Oettler J, Radchenko A, Schultz R, Sharaf M, Trager J, Vesnic A, Wiezik M, Zettel H (2016) Banning paraphylies and executing Linnaean taxonomy is discordant and reduces the evolutionary and semantic information content of biological nomenclature. Insect Soc 63:237–242. doi:10.1007/s00040-016-0467-1

Ward PS, Brady SG, Fisher BL, Schultz TR (2016) Phylogenetic classifications are informative, stable, and pragmatic: the case for monophyletic taxa. Insect Soc doi:10.1007/s00040-016-0516-9