An ant is taking over sacred church forests in Ethiopia

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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.

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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.

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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.

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

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.

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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.

 

References

  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 www.aniek.nyc 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.

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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.

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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?

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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.

References

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: www.rachaelebonoan.com 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.

References

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

Can ants get your pizza delivery faster?

Editor’s note: This is our first guest blogger post for the Insectes Sociaux blog where our blogger chooses an IS article to write about. Previously, bloggers have written about their own research. I hope you enjoy it.

A blog post highlighting the article written by A.A. Yates and P. Nonacs in Insectes Sociaux

Written by Ravindra Palavalli Nettimi

You are hungry. So you order a pizza. *Yummy, yummy, yummy*

But the delivery person is new to the city. What if he or she could use software to find the shortest path with the fewest turns to get you your yummy pizza as fast as possible? Ants could come to your rescue here!

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The pizza delivery problem: how to get to the destination in the most efficient way possible? Illustration: R. Palavalli Nettimi

Many ants face similar maze-like challenge when foraging for honeydew secreted by scale insects in trees. In a recent study published in Insectes Sociaux, A. A. Yates and P. Nonacs from the University of California discovered that ants in a maze take straight line paths with the fewest turns.

To test whether ants can collectively find the shortest paths with the fewest turns, they attached a colony of Linepithema humile ants to a maze consisting of plastic cups connected by plastic tubes and kept some food (mmm… cheese!) in one of the cups as shown below.

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A representation of the experimental array used in the study. Illustration: R. Palavalli Nettimi

Initially, the ants explored all the routes equally and laid pheromone trails as they went. The shortest paths to the food ended up getting more pheromone trails since more ants were likely to have found food sooner than the ants exploring longer paths. (In this case, there are three possible shortest paths, two of them are shown in colour). Each ant laid pheromones and also followed the pheromones trails laid by other ants, creating a positive feedback system leading to the shortest paths getting the most pheromone trails.

This phenomenon is known as the travelling salesman problem. The simple rules that the ants use to find the paths have been coded in software used by companies to find out the optimal paths (shortest distances) to deliver milk across many cities or suburbs.

But often finding the shortest path is not enough. The shortest path could involve more turns and thus a higher chance of getting lost. Or the shortest path could have a traffic jam and lead to reduced speed.

Can the ants come to our rescue again?

The researchers showed that the ants prefer the shortest paths (with fewest turns) when exploring to find the cheese. In the figure above, the green path has two turns, while the orange path has one turn to reach the food. The ants were more likely to follow the orange path than the green one. A path with fewer turns can decrease the chance of foragers getting lost. More turns in the path can make it difficult to learn the path and increase the chances of getting lost and wasting foraging time.

It is likely that the preference for the fewest turns could be a consequence of the ‘wall-following’ tendencies of the ants.

Perhaps all of the rules used by ants could be incorporated into the software to not just find the shortest path, but the most efficient path with fewest turns, or highest speed.

Has your pizza been delivered yet?

 

About the author:
Ravindra Palavalli Nettimi is a PhD student at Macquarie University in Sydney. He writes a blog (https://antists.wordpress.com) and hosts a podcast called Just-questions (https://soundcloud.com/user-951555253 ). Learn more from his website: http://rvndrpn.wixsite.com/ravindra

Interview with a social insect scientist: Lori Lach

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Lori Lach

IS: Who are you and what do you do?

LL:  I am a mother and a wife and a Senior Lecturer (which is in between an Assistant Professor and an Associate Professor in the North American system) in the College of Science and Engineering at James Cook University in Cairns, Australia. I primarily research invasive social insects. In the past few years I’ve also been researching an emerging disease of honey bees and how it affects foraging behavior. I’ve lived in Australia for nearly 11 years and became a dual national (Australian-US) a couple years ago.

IS: How did you end up researching social insects?

LL: I’d been intrigued by ants during an ecology field course as an undergrad, but never really pursued it because at the time I had no idea how that would lead to a job of any kind. By the time I’d started my PhD years later I had become really interested in the consequences of biological invasions. I had the opportunity to do a summer project in Hawai’i while I was still figuring out what I would research, and while I was there I asked every scientist I met which invaders were the most overlooked and likely doing the most damage. Nine out of ten said ants, and the tenth said rats, so ants it was!

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Yellow crazy ants up close. Photo: Dave Wilson

IS: What is your favourite social insect and why?

LL: I’ve been fascinated by yellow crazy ants (Anoplolepis gracilipes) since I first encountered them in Hawai’i at the start of my PhD. They’re just such a conundrum—seemingly so flighty, timid, and disorganized, and yet capable of taking down organisms much larger than they are. Attract a few hundred to a lure, take it away, and it is just mass pandemonium, not the ho-hum retreat of Argentine or big-headed ants. I thought I would get a chance to study them more during my post-doc in Mauritius, but they were really kept in check by Technomyrmex albipes (who would’ve guessed?). But now around Cairns they are a big conservation issue, so I’m in the right place at the right time to work on cracking their secrets.

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A mass of yellow crazy ants next to a rainforest creek. Photo: Frank Teodo

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

LL: This is the hardest question. So far, I think discovery-wise it would have to be finding out the dramatic difference just a few invasive ants in flowers could make to the diversity and behavior of floral visitors, and I was able to show that in three different floral systems. When I started this work, most of the literature had been focused on consequences of the extraordinary abundance achieved by invasive ants and their interactions with ground fauna, so I felt like I was breaking new ground. I’ve had a couple people approach me at conferences and tell me they have been inspired by this work in deciding on their own research path. It is the best feeling to know that my discoveries are leading to others.

The best moment so far is right now. I’ve got some really great students working on a variety of really interesting projects, all involving different species of social insects. I also love that my knowledge of ant ecology, and yellow crazy ants in particular, is of direct use in efforts to protect the World Heritage rainforest from this invader. It’s a privilege to work with a really engaged community that supports science, and it’s exciting to have excellent collaborators with diverse sets of complementary skills.

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

LL: I had a research fellowship when I first started at James Cook University, so teaching has only recently become a substantial part of my work. I currently teach second year Ecology and a module of Field Ecology, and the occasional guest lectures in Tropical Entomology and Invertebrate Biology. Social insects figure prominently in the examples I use because they can be used to illustrate so many concepts, and really, they’re just so cool. Moreover, knowledge of social insect biology is really useful here in the tropics and can be an asset for graduates seeking employment.

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

LL: “Dark Places” by Kate Grenville. I love reading, and I’m opportunistically working my way through Miles Franklin nominated authors. I’d recommend it for the writing, which is exquisite, but not so much for the story. It was an apt title.

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

LL: “Ishmael”, by Daniel Quinn is one of several books I read while I was still considering what kind of career path I should follow. “Silent Spring” by Rachel Carson, was another. These books made me take a step back and question what I wanted my priorities to be. My initial plans were to go into medicine, but I ultimately decided that I should pursue a career in which my efforts were not meant to solely benefit humankind.

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

LL: I’m so lucky—I live in between two World Heritage Areas—the Great Barrier Reef and the Wet Tropics rainforest. So snorkelling, hiking, camping, and just spending time outside with my family top the list. On my to-do list for 2017 is to get back into karate. I was once a brown belt, but will now have to work my way up from white again.

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Lori and her family.

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

LL: I make sure that I stick with my exercise routine and spend time with my family. Stargazing provides instant perspective. It’s a reminder that we’re all just specks in space and time.

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

LL: My collecting kit, because islands are usually great places to collect invasive ants. A guide book to the flora and fauna, because islands often have weird and wonderful biota. And my journal, with lots of blank pages to fill.

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

LL: I owe a lot to whomever it was at the Australian Research Council who decided to offer prestigious early career research awards that explicitly allowed for career interruptions (e.g., parenthood or “misadventure”). At the time I applied, I had worked part-time for five years following the birth of my son in 2007. Of course I still published during that time, but was unlikely to be competitive for jobs against others who had worked full-time. If I hadn’t been awarded one of those fellowships, it is highly unlikely that I would still be a scientist today. I recently learned that until 1966, a woman working in the public service in Australia was forced to resign if she married. So Australia has come a long way.

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

LL: Take advantage of every opportunity to learn skills in a variety of disciplines—ecology, chemistry, biogeography, genetics, genomics, proteomics, bioinformatics—to name a few, because they will probably all enable you to understand these fascinating creatures that little bit more.

 

Sociometry may be exhausting, but it’s important and rewarding

A blog post highlighting the article written by M.L. Smith, M.M. Otswald & T.D. Seeley in Insectes Sociaux

Written by Michael L. Smith


I think Walter Tschinkel (1991) said it best when he wrote: “The list [of sociometric data] is not exhaustive, though collecting the data could be exhausting.” My research into honey bee sociometry is a case study in how right he was.

But let’s start at the beginning: what is sociometry? Sociometry is the description and analysis of the physical and numerical attributes of social insect colonies over their lifetimes (Tschinkel 1991). Sociometric data, therefore, is just about anything that you could measure in a social insect colony throughout its life, such as: the size of the nest, the number of workers, the size of the workers, the size of the food stores, the number of sexuals, etc.

Unfortunately, sociometric data are often not collected, and if they are, they’re rarely reported. It’s probably because collecting these data (plus the analyzing and writing) is tedious work. But it’s rewarding, it’s important information that forms the foundation of future research.

My primary interest is reproductive investment in honey bee colonies. In particular, I wanted to know when workers begin to build the large cells of beeswax comb that they use for rearing reproductive males or “drones.” With this question in mind, I set out to conduct a sociometric study, but not just of drone comb, I’d track the whole colony’s growth and development from birth until death. Surprisingly, this had never been done. Many studies had looked at one or two colony parameters throughout a single season, but only a couple had tracked multiple parameters in concert (Lee & Winston 1985; Pratt 1999). The study that tracked the most parameters simultaneously only did so for the first year (Rangel & Seeley 2012), and so missed out on the production of sexuals that occurs in the second year. It seemed like it was time to conduct a broad sociometric study on honeybee colonies throughout their entire life cycles.

To do this, I built and set up four large observation hives, each one about 1m x 1m. These are larger than standard observation hives, and I chose them because I needed sufficient volume (ca. 40L) for the colony to grow to its full size (Seeley & Morse 1976). I then installed into each observation hive an artificial swarm, and monitored the colonies weekly until they died.

Through the glass of the observation hives, I could observe the colonies without disturbing them. I could monitor the number of inhabitants, the growth of the comb, and the contents of the comb, all traced upon a sheet of plastic placed atop the glass of the observation hive. Together with a keen undergraduate, Maddie Ostwald, we tracked honey bee colonies from birth until death while recording worker population, drone population, comb area, comb use (cells holding brood, pollen, honey, or nothing), swarming and secondary swarming events, and time of death. This began in July 2012 and continued until January 2014, and that doesn’t count the time it took to transcribe the comb areas from the plastic sheets!

What do we get at the end of it all? Well, first and foremost, I think it’s a great way to get extremely familiar with your study organism. I grew fond of my colonies, each one with its own personality. One hive was in my office, so I’d hear them buzzing along throughout the day- the perfect office mate. Second, I’m now able to frame my experimental work within the context of these observational descriptions. For example, I now know that although all four colonies built drone comb in their first year, none of them used the drone comb for rearing drones until the second year. Despite having only four colonies, we observed a diversity of life-history strategies, including one colony that attempted to reproduce by producing queen-laid drones in worker cells (the drones were two-thirds smaller than those produced by the other colonies). We also found that drones tend to stay at home when a swarm departs, presumably because they have higher reproductive success at home, but the workers will quickly cull the drones if food stores are low. These highlights, of course, are biased by my interest in drones, so please check out the paper if you’d like to know more (Smith et al. 2016). Lastly, sociometric data are a valuable resource for all social insect biologists, and we cannot conduct comparative analyses without good descriptions of the natural growth and development of many social insect colonies.

I encourage you to think of your favorite social insect species. Is there a paper out there that describes, in painstaking detail, everything that you could possibly count, measure, and describe, from colony founding to colony death? If not, then maybe this is your chance to make it happen!

 

References

Lee, P.C. & Winston, M.L., 1985. The effect of swarm size and date of issue on comb construction in newly founded colonies of honeybees (Apis mellifera L.). Canadian Journal of Zoology, 63(3), pp.524–527.

Pratt, S.C., 1999. Optimal timing of comb construction by honeybee (Apis mellifera) colonies: a dynamic programming model and experimental tests. Behavioral Ecology and Sociobiology, 46(1), pp.30–42.

Rangel, J. & Seeley, T.D., 2012. Colony fissioning in honey bees: size and significance of the swarm fraction. Insectes Sociaux, 59(4), pp.453–462.

Seeley, T.D. & Morse, R.A., 1976. The nest of the honey bee (Apis mellifera L.). Insectes Sociaux, 23(4), pp.495–512.

Smith, M.L., Ostwald, M.M. & Seeley, T.D. 2016. Honey bee sociometry: tracking honey bee colonies and their nest contents from colony founding until death. Insectes Sociaux.

Tschinkel, W.R., 1991. Insect sociometry, a field in search of data. Insectes Sociaux, 38(1), pp.77–82.

The winner takes it all, the loser standing small!

A blog post highlighting the article written by Bang and Gadagkar in Insectes Sociaux

Written by Alok Bang

Remember the song by ABBA, ‘The winner takes it all’? In a nutshell, the fate of the dejected lover ABBA portrays can be extended to any conflict. Winners keep winning, and monopolise resources and opportunities. Losers keep losing and forego everything. Or, do they really?

But before coming to that, let’s discuss conflict in animal societies. Why is conflict of utmost interest and importance? For the simple reason, that it is omnipresent. Think of societies most harmonious and in unison, such as those of paper wasps, honey bees, ants and termites – where tens to hundreds and sometimes millions of individuals live and work together – are strewn with conflict. Individuals in these seemingly cooperative societies fight with each other often, over food, mates, territories and other opportunities. Who wins and who loses, thus, has a direct impact on an individual’s survival and reproduction, thereby affecting its evolutionary fitness.

Classically, researchers have focussed on role of individual characteristics such as age, size, weight, hormones and genes, in making winners and losers. While this approach has been important, it has excluded the role an individual’s social environment might play. Environment may influence fighting behaviour, fighting abilities, strength, and finally self-assessment of one’s strength, but this has been largely ignored.

Take the case of self-assessment of one’s fighting ability. When individuals fight, are they winning or losing merely based on their strengths, or does self-assessment of strength influence the outcome of a contest? Human history is laden with examples of an underdog, who is physically average or even weak, defeating a stronger opponent, because of a heightened perception of her strength. Similarly, a strong individual is known to lose a contest if she has a diminished self-assessment of her strength. Self-assessment can thus be influential – as much if not more – than the actual strength, in deciding the outcome of a fight.

In the past two decades, the phenomenon of winner-loser effects have come to the forefront of such enquiries into external determinants of fighting abilities and contest outcome. Simply put, they refer to an increased probability of winning or losing a contest based on prior experience of winning or losing, respectively, even if everything else is randomised. A prior experience of winning may enhance and a prior experience of losing may diminish an individual’s perception of its own fighting ability; thereby, affecting the contest outcome. Such studies have been mostly performed in vertebrates and research on the role the environment plays in conflict outcome in invertebrates is severely lacking.

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A typical Ropalidia marginata colony. R. marginata is found abundantly in peninsular India. Photo credit: Thresiamma Varghese.

In the first study of its kind that investigated the role of prior experience on current contest outcome in a eusocial species, we chose the primitively eusocial Indian paper wasp, Ropalidia marginata as the model system. To control for a wasp’s environmental experience, the focal individuals to be included in the experiments had to be devoid of any prior fighting related experience. This was achieved by bringing adult-less colonies of R. marginata into a controlled environment, keeping thorough census records of all individuals being born on a colony, and isolating these individuals as soon as they were born.

The other important step was the method of choosing focal individuals for winner and loser effect experiments. We achieved random-selection by giving pre-decided contest outcomes to random focal individuals in the first contest, independent of their intrinsic strengths. We chose this method because these experiments aim to investigate the effect of experience, and not strength, on the contest outcome.

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A lone R. marginata female. R. marginata females, like in many other paper wasp societies, can found new colonies individually as well as in a group. Photo credit: Alok Bang

In experiments performed to investigate winner effects, a pre-decided winning experience was given to a random focal individual by pairing it with an extremely weak individual (termed habitual loser) of the population. This ensured that the pool of focal individuals used for testing winner effects did not include only strong individuals, but included individuals with a wide range of intrinsic strengths. Similarly, in experiments to investigate loser effects, a pre-decided losing experience was given to a random focal individual by pairing it with an extremely strong individual (termed habitual winner) of the population. This, in turn, ensured that the pool of focal individuals used for testing loser effects did not have only weak individuals, but included individuals with a wide range of intrinsic strengths. The focal individuals with such pre-decided contests were then paired with a random naive individual in the second contest.

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R. marginata females engaged in a dominance-subordinate interaction. The behaviour displayed here is called ‘sit over’, where the dominant individual sits over the subordinate individual and renders her immobile. Fights such as these are quite common in R. marginata. This helps to establish a dominance hierarchy between individuals, and has important implication on survival and reproduction of individuals, and work regulation in the colony. Photo credit: Alok Bang.

Each experiment thus consisted of a first contest between a focal individual and a habitual loser/winner, giving it a pre-decided contest that occurred for one hour, followed by a 45-minute gap, which then was followed by a second contest of one-hour between the focal individual with a random naïve opponent. In such an experimental set-up, a second successive win (or loss), in significantly more than half the cases, would indicate that the individuals’ self-perception was impacted due to their prior experience. During all these contests, dominance-subordinate interactions between individuals were observed, and winners and losers of the contests were declared. All experiments were carried out  blind.

We indeed found that there was a significantly high number of pairs in which a win was followed by a second win, and a significantly high number of pairs in which a loss was followed by a second loss, indicating that both winner and loser effects are present in the Indian paper wasp, R. marginata.

Winner effects may evolve due to advantages associated with winning, but why would a species evolve loser effects? Moreover, how do two such apparently opposing phenomena concurrently exist in a species? Winner and loser effects are most likely independent or even interdependent effects. If self-assessment of winners and losers are independently advantageous, these effects would exert independent feedback loops on individuals and co-exist. For example, winning a contest may allow winners a higher access to resources and mates, thus developing and reinforcing winner effects. Losing a contest on the other hand, though seemingly disadvantageous, may allow individuals to forego costs associated with fighting such as injuries, exhaustion and death. If the benefits of avoiding these costs are much higher than the benefits acquired from winning, loser effects will simultaneously develop in the population.

Here we show that wasp behaviour is not only governed by their own internal constitution, but to a considerable extent by their surroundings. The role of external and social determinants of behaviour balances the hitherto unduly skewed importance given to individual characteristics.

Finally, is the Indian paper wasp R. marginata a unique and only eusocial species that displays winner-loser effects? It is definitely the first eusocial species, but we believe it will not be the last. The uniqueness of R. marginata in this regard may have less to do with ecology of the species, and more due to lack of such investigations in other social insects. This study should steer efforts towards finding the presence, extent and longevity of winner-loser effects in other social species. A comparative approach to studying proximate and ultimate factors governing winner and loser effects in social species will be key to understanding sociobiology of group living animals.

Facultative slave-making ants tolerate alien slaves but not their masters

A blog post highlighting the article written by Włodarczyk in Insectes Sociaux

Written by Tomasz Włodarczyk

Many ant species in nature are closely associated with other ant species. The closest form of such an association is called a mixed colony where ants of both species inhabit common nest, share food and raise their brood side by side. Mixed colonies arise as a result of social parasitism when one species exploits the labor of the other, such as in slave-making ant species. Slave-maker ants raid the nests of the host species, steal the pupae and bring them back to their home nests. Newly-emerged individuals integrate into the parasite’s society and perform all domestic duties.

In the lab, we can also create mixed colonies using species that would never form such an association in nature. The species don’t even have to co-exist geographically. This is because ants learn (imprint) colony odor after eclosion from pupae and use it as a template for subsequent nestmate recognition. Thus, by putting together callow ants of different species we can create a mixed colony of individuals that have imprinted on the odor of each other.

As a part of my PhD project I investigated the recognition behavior of ants using a colony of the facultative slave-making ant species, Formica sanguinea. By supplying them with pupae of Formica polyctena or F. rufa -which soon emerged- I formed mixed colonies (Włodarczyk 2012, Włodarczyk and Szczepaniak 2014). These experiments were inspired by the studies conducted by Wojciech Czechowski (1994) whose results suggested that F. sanguinea ants acquire their recognition signature form their slaves, as in the obligate slave-making species Polyergus samurai (Yamaoka 1990).

Excavation

Formica sanguinea is a facultative slave-making species enslaving ants from the subgenus Serviformica. Here, a colony with black F. fusca slaves has been excavated.

Later I became curious about how things look in the case of F. sanguinea colonies containing the most frequently used slave species, F. fusca. Results of chemical studies revealed that odor of F. sanguinea ants is quite different from that of its host species (Martin et al. 2008, Włodarczyk and Szczepaniak in prep.). Moreover, we found that enslaved F. fusca ants develop a chemical recognition signature which is intermediate between that of their parasite and ants from free-living colonies (Włodarczyk and Szczepaniak in prep.). This raised the question about how recognition cue diversity in F. sanguinea colonies affect the recognition abilities of ants. Even more interesting was whether there are differences in the recognition abilities between F. sanguinea and F. fusca ants given that the parasite is the only party to be under selective pressure to live in such a condition.

I collected eight queenright F. sanguinea colonies containing F. fusca slaves and maintained in the the laboratory. The slave-making F. sanguinea ants and their slaves were exposed on a Petri dish to anesthetized ants from alien colonies. I measured the number of aggressive behaviors in various encounter combinations. I showed that F. sanguinea ants are able to discriminate other individuals from the same species from alien colonies towards which they exhibit aggressive behavior. However, slaves from alien colonies were generally tolerated. This result supports the hypothesis that F. sanguinea ants are intrinsically tolerant to individuals whose odor indicates that they are slaves. Otherwise slave-making ants might accidentally attack their own slaves, which possess a recognition signature that deviates from that of the other slaves. This situation would arise when slaves from new source colony appear in the slave-maker’s society.

The other result was that slaves (F. fusca) are poor at discriminating slave-making ants and slaves from alien colonies and do not exhibit an overt aggression toward them. This could be explained by the high within-colony recognition cue diversity that hampers formation of an accurate template during colony’s odor learning phase. This is intuitive explanation since it might be hard to recognize an object of a given class when this class is relatively heterogeneous. Thus, there is no recognition barrier for F. sanguinea ants to take over slaves from alien colonies. However, such a phenomenon has not been recorded for F. sanguinea ants. Therefore we can hypothesize that intraspecific raids play at best very limited role as a way of slave gaining.

Formica

Formica fusca slaves showing aggressive behavior towards an anesthetized conspecific ant.

Moreover, I conducted an experiment in which slaves and slave-makers were reared separately. After about 2-month period, ex-slaves elicited aggression in ants from stock colonies (both in slave-makers and in slaves). Conversely, slave-makers separated from slaves were still treated as nestmates. This result suggests that F. sanguinea exert a strong impact on the odor of F. fusca ants, possibly by the transfer of recognition cues during food exchange.

The results of my study highlight that selective pressures associated with different life histories can lead to differences in recognition systems between social insect species.

 

References

Czechowski W (1994) Impact of atypical slaves on intraspecific relations in Formica sanguinea Latr. (Hymenoptera, Formicidae). Bull Pol Acad Sci 42(4):345–350

Martin SJ, Helantera H, Drijfhout FP (2008) Evolution of species-specific cuticular hydrocarbon patterns in Formica ants. Biol J Linn Soc 95:131–140

Włodarczyk, T (2012) Recognition of individuals from mixed colony by Formica sanguinea and Formica polyctena ants. J Insect Behav 25: 105–113

Włodarczyk T, Szczepaniak L (2014) Incomplete homogenization of chemical recognition labels between Formica sanguinea and Formica rufa ants living in a mixed colony. J Insect Sci 14:214

Yamaoka R (1990) Chemical approach to understanding interactions among organisms. Physiol Ecol Japan 27:31–52

Interview with a social insect scientist: Mark Brown

IS: Who are you and what do you do?

MB: Mark Brown. I’m a Professor at Royal Holloway University of London, where I lead a research group that seeks to understand host-pathogen interactions in bumblebees, as well as aiding in the conservation of bumblebees. We also enjoy investigating other aspects of social insect biology.

IS: How did you end up researching social insects?

MB: In my 2nd year at university, I was lucky to have Deborah Gordon – ant biologist – as one of my tutors. After teaching me for a term, she asked me if I’d like to come and work for her as a field assistant in the desert in Arizona for the summer. I said yes, to a large degree because I thought it was an opportunity to combine biology with travel. But then I met the ants and fell in love (with the ants, I should add!), and since then it’s been social insects all the way!

IS: What is your favourite social insect and why?

MB: Can I ask for two? The first – Messor andrei – was the subject of my PhD research. They’re beautiful black ants, who make a habit of carrying seeds like parasols back to their nest. The second – Bombus lapidarius – I have yet to work on, but they’re a beautifully smart bumblebee that make the most elegant nests.

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Bombus lapidarius, one of Mark’s favourite species. Photo credit: Jürgen Mangelsdorf / flickr

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

MB: That’s a tough one. Discovering that the parasite Crithidia bombi had a major impact on bumblebee fitness has to be up there, as before then it was seemingly a parasite without virulence. However, I think that work with Matthias Fürst, Dino McMahon, Juliet Osborne, and Robert Paxton, where we showed that honey bee pathogens spill over into wild bumblebee populations, is at the top. Understanding the dynamics of viral diseases in the field has important practical implications, as well as being exciting from a pure research perspective, and so our finding has had a real impact on the field.

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

MB: I teach courses in invertebrate biology, conservation biology, and a field course in ecology and conservation on the island of Samos, Greece. It’s surprising how often my examples involve social insects of one kind or another. 😉

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

MB: “A Place of Greater Safety” by Hilary Mantel. A character-focused history of the firestorm that was the French Revolution, this is definitely worth reading! Mantel writes incredibly incisively about people and their motivations, and how this shapes history. For anyone who wants to understand the politics of science, and how this can impact careers and the trajectory of science itself, this is a great primer.

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

MB: I read “The Trouble with Lichen” by John Wyndham when I was a teenager. This inspired me to become a research scientist (in particular, a biochemist, which lasted only until I realised that the ‘bio’ aspect was rather limited), and also to recognise that gender has a significant impact on recognition and career advancement in science (this was long before I’d heard of Rosalind Franklin). We still have a long way to go to make science a level-playing field for all genders and orientations, but it’s a goal we have to reach.

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

MB: Reading fantasy novels, and spending time with my nieces. It would be walking safaris through the Zambian bush, but I can’t afford to do it often enough to call it a hobby!

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

MB: I remember that I’m a very lucky man – I have a family, friends, and a job I love – and try to focus on the day-to-day until I get my perspective back.

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

MB: My husband, good Swiss chocolate, and an endless supply of paperback books (none of these need explanation!).

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

MB: My PhD supervisor, Deborah Gordon, taught me how to look at ants, and how to think and write like a scientist. Paul Schmid-Hempel, my post-doc boss, introduced me to the intriguing world of host-parasite interactions, and also taught me how to play the scientific game. I owe them both a huge debt.

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

MB: Get outside and watch the animals. If you can spend hours watching ants or bees (apologies to my termite and wasp colleagues!), and still come away fascinated, then you’ve got a good foundation to build on. If you decide it’s not for you, get another job, earn loads of money, and set up a charitable foundation to fund the research you’d like to see done.

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Messor andrei, Mark’s first ant love. Photo credit: photographer (unknown) and http://www.antweb.org / Wikimedia commons