Anurag Agrawal: Needing and eating the milkweed

AgrawalU.S. agriculture is based on ideas that make me scratch my head. We typically grow plants that are not native to North America, we grow them as annuals, and we usually only care about one product from the crop, like the tomatoes that give us ketchup and pizza.

And we don’t like weeds. Why would we? They take resources away from our crops, reduce yields more than insect pests or disease, they’re hard to get rid of, and they might give you a rash. But there are few plants more useful, easy to cultivate, and environmentally friendly than the milkweed. The milkweed takes its ill name from the sticky rubbery latex that oozes out when you break the leaves, it’s the monarch butterflies only food, and it is a native meadow plant. Milkweed has sometimes received a bad rep, and perhaps for good reason; they can be poisonous to livestock, they are hard to get rid of, and they do reduce crop yields. But what about milkweed as a crop?

AgrawalThomas Edison showed that milkweed’s milky latex could be used to make rubber. The oil pressed from the seed has industrial applications as a lubricant, and even value in the kitchen and as a skin balm. And as a specialty item, acclaimed for its hypoallergenic fibers, milkweed’s seed fluff that carries milkweed seeds in the wind, is being used to stuff pillows and blankets. Perhaps more surprising, the same fluff is highly absorbent of oils, and is now being sold in kits to clean up oil tanker spills. The fibers from milkweed stems make excellent rope and were used by Native Americans for centuries. More than two hundred years ago, the French were using American milkweed fibers Agrawalto make beautiful cloths, said to be more radiant and velvety than fine silk. And chemically, milkweeds were used medicinally by Native Americans since the dawn of civilization, with a potential for use in modern medicine.  This is a diverse plant with a lot to offer.  Why wouldn’t we cultivate this plant, not only for its stem fibers, seed oils, pillowy fluff, rubbery latex, and medicines, but also in support of the dwindling populations of monarch butterflies?

Ever since the four lowest years of monarch butterfly populations between 2012 and 2015, planting milkweeds for monarchs has been on the tips of a lot of tongues. For most insects that eat plants, however, their populations are not limited by the availability of leaves.  Instead, their predators typically keep them in check, or as in the case of monarchs, there may be constraints Agrawalduring other parts of their annual cycle. Monarchs travel through vast expanses from Mexico to Canada, tasting their way as they go. They tolerate poisons in the milkweed plant; indeed, they are dependent on milkweed as their only food source as a caterpillar. Nearly all mating, egg-laying, and milkweed-eating occurs in the United States and Canada. And each autumn monarchs travel to Mexico, some 3,000 miles, fueled only by water and flower nectar.

All parts of the monarch’s unfathomable annual migratory cycle should be observed and studied. My own research has suggested that habitat destruction in the U.S., lack of flower resources, and logging at the overwintering sites in central Mexico are all contributing to the decline of monarch butterflies. Lack of milkweed does not seem to be causing the decline of monarchs. Nonetheless, planting native milkweeds can only help the cause of conserving monarch butterflies, but it is not the only answer. And of course we humans need our corn and soy, and we love our broccoli and strawberries, so is cultivating milkweed really something to consider?

We humans, with our highly sensitive pallets, do the one thing that monarch butterflies don’t do. We cook. And the invention of cooking foods has been deemed one of the greatest advances in human evolution. Cooking certainly reduces the time spent chewing and digesting, and perhaps more importantly, cooking opens up much of the botanical world for human consumption, because heat can break down plant poisons.

AgrawalEuell Gibbons, the famed proponent of wild plant edibles in the 1970s, was a huge advocate of eating milkweed. The shoots of new stems of the eastern “common milkweed” are my personal favorite. I simply pull them up when they are about 6-8 inches tall and eat them like asparagus. Gibbons recommended pouring boiling water over the vegetables in a pot, then heating only to regain the boil, and pouring off the water before sautéing. You can pick several times and the shoots keep coming. With some preparation, the other parts of the milkweed plant can be eaten too, and enjoyed like spinach, broccoli, and okra.

At the end of summer, many insects have enjoyed the benefits of eating milkweed, especially the monarch butterfly. Any boost we could give to the monarch population may help use preserve it in perpetuity. But the real value in cultivating milkweed as a crop is that it has a lot to offer, from medicines to fibers to oils. It is native and perennial, and can be grown locally and abundantly.  Let’s give this weed a chance.

Anurag Agrawal is a professor in the Department of Ecology and Evolutionary Biology and the Department of Entomology at Cornell University. He is the author of Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution.


Andrew Lo on Adaptive Markets: Financial Evolution at the Speed of Thought

Half of all Americans have money in the stock market, yet economists can’t agree on whether investors and markets are rational and efficient, as modern financial theory assumes, or irrational and inefficient, as behavioral economists believe. In this groundbreaking book, Andrew Lo cuts through this debate with a new framework, the Adaptive Markets Hypothesis, in which rationality and irrationality coexist. Adaptive Markets shows that the theory of market efficiency isn’t wrong but merely incomplete. Lo’s new paradigm explains how financial evolution shapes behavior and markets at the speed of thought. An ambitious new answer to fundamental questions in economics, Adaptive Markets is essential reading for anyone who wants to know how markets really work. We asked him to explain the Adaptive Markets Hypothesis, the strengths and limitations on the current theories, and how this new thinking can be practically applied.

What led you to write this book?

AL: Ever since I was a graduate student in economics, I’ve been struggling with the uncomfortable observation that economic theory doesn’t seem to work in practice. As elegant as this theory is, there are so many examples where the data just don’t support the theory that, after a while, I started wondering just how useful our theories were. For example, stock market prices don’t follow random walks, market prices don’t always seem rational, and people often make poor decisions, especially when it comes to financial matters. But it takes a theory to beat a theory. Rather than just criticizing existing theories, I decided to develop an alternative—this book describes the personal journey I took to arrive at that alternative, which I call the Adaptive Markets Hypothesis.

What’s the Adaptive Markets Hypothesis?

AL: The Adaptive Markets Hypothesis is my solution to the longstanding debate in financial economics between two competing camps. One camp consists of the disciples of the Efficient Markets Hypothesis, who believe that investors are rational decision makers and market prices fully reflect all available information. The opposing camp consists of the psychologists and behavioral economists who believe that investors are irrational and market prices are driven by “animal spirits.” It turns out that both camps have correctly captured certain aspects of human behavior, but neither camp offers a complete picture of how investors and markets behave. The Adaptive Markets Hypothesis fills this gap.


AL: By drawing on recent research in psychology, neuroscience, evolutionary biology, and artificial intelligence, I show that human behavior is the result of several different components of the brain, some of which produce rational behavior while others produce more instinctive emotional behavior. These components often work together, but occasionally they compete with each other. And for obvious evolutionary reasons, rationality can be trumped by emotion and instinct when we’re confronted with extreme circumstances like physical threats—we “freak out.” The problem is that these hardwired responses to physical threats are also triggered by financial threats, and freaking out is generally not the best way to deal with such threats. Therefore, investors and markets have a split personality: sometimes they’re quite rational but every so often, they freak out.

Are you suggesting that the Efficient Markets Hypothesis, which dominates financial thinking today, is wrong?

AL: No! On the contrary, the Efficient Markets Hypothesis is one of the most useful, powerful, and beautiful pieces of economic reasoning that economists have ever proposed. Generations of investors and portfolio managers have been saved from bad investment decisions because of the Efficient Markets Hypothesis, which says that if something seems too good to be true, it probably is. The Efficient Markets Hypothesis is not wrong; it’s merely incomplete. Its focus is the behavior of investors and markets in normal business environments, where the “wisdom of crowds” rules the day. What’s missing is the “madness of mobs,” when investors are reacting emotionally and instinctively in response to extreme business environments—good or bad—leading either to irrational exuberance or panic selling. The Adaptive Markets Hypothesis provides a more complete framework in which both types of behaviors are possible. The combination of these behaviors yields a much richer set of implications for price dynamics, investment strategies, risk management, and financial regulation.

Who is the intended audience for this book?

AL: My intention was to write this book for the general reader, but only time will tell whether or not I’ve succeeded. In fact, I’m hoping that there’s something for everyone in this book. For example, readers wondering whether or not it’s possible to beat the stock market using mathematical models will want to read Chapter 2, “If You’re So Smart, Why Aren’t You Rich?” For readers already convinced that it’s possible and want to understand the neuroscientific basis of irrational behavior, they’ll want to read Chapter 3, “If You’re So Rich, Why Aren’t You Smart?” No book on finance would be complete without a discussion of how the recent financial crisis could have happened to us—a country with one of the most sophisticated financial systems in the world—and that’s Chapter 9, “Fear, Greed, and Financial Crisis.” And for readers interested in getting a glimpse of the future of the financial industry and the amazing things that can be accomplished with finance if used properly, there’s Chapter 12, “To Boldly Go Where No Financier Has Gone Before.” Although the book is based on my academic research, I’ve worked hard to translate “academic-speak” into plain English, using simple analogies and real-life examples to make the research come alive. In fact, there’s not a single equation or mathematical formula in the book, which is no easy feat for someone from MIT!

In Adaptive Markets you take an interdisciplinary view of financial markets, bringing in cognitive neuroscience, biology, computer science, and engineering. How did you come to bring all of these seemingly disparate fields together and why is that important?

AL: Although I do enjoy learning new things and have broad-ranging interests, when I started my academic career as a financial economist, I had no interest or intention in doing “interdisciplinary” research. I was perfectly happy spending my days and nights working on traditional neoclassical financial economics—portfolio theory, derivatives pricing models, asset pricing models, financial econometrics, and so on. But the more I tried to fit financial theories to data, the more frustrated I became that these theories performed so poorly. So I started trying to understand why the theories broke down and how they could be fixed. I began by studying behavioral economics and finance, which led me to psychology, which then to the cognitive neurosciences, and so on. I was dragged—sometimes kicking and screaming—from one field of study to the next in my quest to understand why financial markets don’t work the way we think (and want them to). This process ultimately led me to the Adaptive Markets Hypothesis, which is a very satisfying (for me, at least) integration of various disciplines that have something to say about human behavior. I’m especially pleased by the fact that Adaptive Markets reconciles the two competing schools of thought in financial economics, both of which are compelling in their own right even though they’re incomplete.

Why do we need to understand the evolution of finance?

AL: Many authors and academics will use evolution as a metaphor when referring to the impact of change. In Adaptive Markets, I use evolution quite literally because financial markets and institutions are nothing short of evolutionary adaptations that Homo sapiens has developed to improve our chances of survival. Therefore, if we really want to understand how the financial system works, how it changes over time and circumstances, and what we can do to improve it, we need to understand the evolution of finance. And unlike animal species, which evolve from one generation to the next, the financial system evolves at the speed of thought.

You argue that economics wishes it were more like the hard science of physics where 99% of all observable phenomena can be explained with three laws. Will we ever have a complete understanding of how financial markets function?

AL: It’s true that most economists—myself included—suffer from a psychological disorder called “physics envy.” We wish we could explain 99% of economic behavior with three laws like the physicists but this is a pipe dream. The great physicist Richard Feynman put it best when he said, “Imagine how much harder physics would be if electrons had feelings!” I tell all my students at the start of the semester that all economic theories are approximations to a much more complex reality, so the key question for investors and portfolio managers is not “is the theory correct?” but rather, “how good is the approximation?” The answer to this question lies largely in the environment, which plays a huge role in evolutionary theories. Whether we’ll ever be able to develop a truly complete theory of human behavior—and, therefore, how financial markets function—is hard to say. But I do believe that we can get much closer to that complete theory through the Adaptive Markets Hypothesis.

How can investors and portfolio managers incorporate the Adaptive Markets Hypothesis into their investment philosophies?

AL: The Adaptive Markets Hypothesis has a relatively straightforward but sweeping implication for all investment philosophies, and that has to do with change. During normal business environments, the principles of Efficient Markets are an excellent approximation to reality. For example, from the 1930s to the early 2000s, a period where the U.S. stock market had relatively consistent average returns and volatility, a long-only passive investment strategy of 60% stocks and 40% bonds produced pretty decent returns, particularly for those who were investing over a 10- or 20-year horizon. The problem is that this approach doesn’t always work. When market conditions change and we experience large macro shocks like the financial crisis of 2008, then simple heuristics like 60/40 no longer work as well because financial markets have changed in their dynamics. Today’s markets are now much more responsive to intervention by governments and their central banks and punctuated by the irregular cycle of fear and greed. So since 2007 and 2008, we’ve seen a very different market dynamic than over the previous six decades. The point of Adaptive Markets is not simply to be wedded to any static theory, but rather to understand how the nature of markets can change. And once it does change, we need to change with it. John Maynard Keynes put it best when, in responding to criticism that he flip-flopped on the gold standard, he said, “When the facts change, sir, I change my mind. What do you do?”

Can you give an example of how change might impact today’s investors?

AL: One important implication of Adaptive Markets for investors and portfolio managers is that passive investing is changing and we have to adapt. John Bogle—the founder of the Vanguard Group and the father of passive investing and index funds—had an incredibly important insight in the 1970s which he calls the “Cost Matters Hypothesis:” reducing trading costs can have a huge impact on wealth accumulation. Bogle has done more for the individual investor than anyone else I can think of; he democratized the investment process. Thanks to technological innovations like automated trading, electronic market-making, and big data analytics, we’re ready to take the next evolutionary step that builds on Bogle’s legacy. For example, like the trend in healthcare towards personalized medicine, we can now create personalized indexes that are passive portfolios designed to achieve specific goals for a given individual. You might be more risk tolerant than your neighbor so your portfolio will have more equities, but because you work in the financial industry and she works in big pharma, your personalized portfolio will have fewer financial stocks and hers will have fewer biopharma stocks. Also, personalized indexes can manage the risk more actively to suit an individual’s threshold of “pain.” Current financial wisdom criticizes investors who don’t invest for the long run, and I’ve always thought such criticism to be terribly unfair. After all, how easy is it for someone to stick with an investment that’s lost 50% of its value over just a few months? Well, that’s exactly what happened between the fourth quarter of 2008 and the first quarter of 2009. Traditional investment advice is a bit like trying to prevent teenage pregnancies by asking teenagers to abstain—it’s not bad advice, but it’s unrealistic. Why not manage the risk of an individual’s portfolio more actively so as to reduce the chances of freaking out?

Finance has developed a bad reputation in the popular press, particularly in the aftermath of the recent financial crisis. Does the Adaptive Markets Hypothesis have anything to say about this and how things can be improved?

AL: Absolutely. At the heart of all bad behavior, regardless of the industry or context, is human nature. Humans are the Curious George of the animal kingdom, but there’s no “man in the yellow hat” to bail us out when we get into trouble. Homo sapiens has evolved in some remarkable ways and we’re capable of extraordinary things, both good and bad. The same social and cultural forces that give rise to wonderful organizations like the Peace Corps, the Red Cross, and Doctors without Borders can sometimes lead to much darker and destructive organizations. The only way for us to deal more effectively with the negative aspects of society is to acknowledge this dual nature of human behavior. Chapter 11 of Adaptive Markets, titled “Fixing Finance,” is devoted entirely to this objective. We have to be careful not to throw out the baby with the bathwater—the financial system definitely can be improved, but we shouldn’t vilify this critically important industry because of a few bad actors.

What are some specific proposals for how to fix finance?

AL: Well, before we can fix finance, we need to understand where financial crises come from, and the Adaptive Markets Hypothesis has a clear answer: crises are the product of human behavior coupled with free enterprise. If you can eliminate one or both of these two components, you can eliminate financial crises. Otherwise, financial crises are an avoidable fact of modern life. Human misbehavior is a force of Nature, not unlike hurricanes, flash floods, or earthquakes, and it’s not possible to legislate away these natural disasters. But this doesn’t mean we can do anything about it—we may not be able to prevent hurricanes from occurring, but we can do a great deal to prepare for them and reduce the damage they do. We can do a lot to prepare for financial crises and reduce the damage they do to those individuals and institutions least able to withstand their devastating consequences. This perspective is important because it goes against the traditional narrative that financial crises are caused by a few greedy unscrupulous financiers and once we put them in jail, we’ve taken care of the problem. The Adaptive Markets perspective suggests something different: the problem is us. Specific proposals for dealing with crises include: using new technologies in data science to measure economic activity and construct early warning indicators of impending crises; studying crises systematically like the way the National Transportation Safety Board studies airplane crashes so we know how to make the financial system safer; creating adaptive regulations that change with the environment, becoming more restrictive during booms and less restrictive during busts; and systematically measuring individual behavior and corporate culture quantitatively so we can engage in “behavioral risk management.”

Now that you’ve written this book, where do you see your research going from here?

AL: Well, this is still early days for the Adaptive Markets Hypothesis. There’s so much left to be done in exploring the implications of the theory and testing the implications empirically and experimentally whenever possible. The Efficient Markets Hypothesis took decades and hundreds of academic studies to get established, and the same will be true of this one. One of my goals in writing this book is to motivate my academic and industry colleagues to start this vetting process. In the same way that Darwin’s theory of evolution had to be tested and challenged from many different perspectives, the Adaptive Markets Hypothesis has to go through the gauntlet of academic scrutiny. One important implication of the Adaptive Markets perspective is that we need to change the way we collect data and test theories in financial economics. For example, traditional tests of financial theories involve collecting stock market prices and analyzing the statistical properties of their risks and returns. Contrast this approach with how an ecologist would study a newly discovered tropical island in an effort to preserve it. He would begin by first cataloguing the flora and fauna, identifying the key species, and measuring their biomasses and behaviors. Next, he would determine the food chain, environmental threats, and predator/prey relationships, and then turn to population dynamics in the context of the changing environment. Ultimately, such a process would lead to a much deeper understanding of the entire ecosystem, allowing ecologists to determine the best way to ensure the long-term health and sustainability of that island. Imagine doing the same thing with the financial industry. We would begin by cataloguing the different types of financial institutions and investors, measuring their financial biomass, and identifying key species—banks, hedge funds, pension funds, retail investors, regulators, etc.—and their behaviors. Then we would determine the various types of business relationships and interdependencies among these species, which are critical for mapping the population dynamics of this financial ecosystem. This approach seems sensible enough, but it’s not yet being done today (except by my collaborators and me!).

How do you continue to evolve your own thinking? What do you do?

AL: Someone very wise once said that the beginning of wisdom is humility, and I’m convinced that this is how we make progress as a civilization. Once we’re convinced that we have all the answers, we stop asking new questions and learning. So I’m continually looking for new ways to understand financial market behavior, and constantly humbled by how little I know compared to how much we have yet to discover. In this respect, I guess I’m an intellectual opportunist—I don’t care where an idea comes from or what academic discipline it belongs to; if it gives me new insight into an existing problem, I’ll use it and build on it. I’m currently working on several applications of the Adaptive Markets Hypothesis to investments, risk management, and financial regulation, and also hoping to test the theory in the context of individual and institutional investment decisions. The initial results are quite promising and show that financial industry participants adapt much more quickly than we thought. These results point to several important unintended consequences that have clear implications for how we should regulate the industry so as to reduce the chances of another financial crisis.

Andrew W. Lo is the Charles E. and Susan T. Harris Professor at the MIT Sloan School of LoManagement and director of the MIT Laboratory for Financial Engineering. He is the author of Hedge Funds and Adaptive Markets: Financial Evolution at the Speed of Thought. He is also the founder of AlphaSimplex Group, a quantitative investment management company based in Cambridge, Massachusetts.

Anurag Agrawal: Monarchs vs. Milkweed

by Anurag Agrawal

Coevolution is a special kind of evolution. And monarchs and milkweeds exemplify this special process. In particular, what makes coevolution special is reciprocity. In other words, coevolution is one species that evolves in response to the other, and the other species evolves in response to the first. Thus, it is a back-and-forth that has the potential to spiral out of control. In some arms races, the two organisms both benefit, such as that between some pollinators and flowering plants. But coevolution is more common among antagonists, like predators and their prey.

When biologists first described coevolution, they likened it to an arms race. An arms race, such as that between political entities, occurs when two nations reciprocally increase their armament in response to each other. So how does an arms race between monarchs and milkweeds, or between cats and mice, or between lions and wildebeest, or between plants and their pathogenic fungi, proceed? When coevolution occurs, it proceeds with “defense” and “counter defense.” And one of the few rules of coevolution is that for every defense that a plant or prey mounts, the predator mounts a counter defense, or an exploitative strategy to overcome the defense.

Once a monarch butterfly lays an egg on a milkweed plant, the natural history of coevolution unfolds. For every defense that the plant mounts, milkweed mounts a counter defense. Once the caterpillar hatches, it must contend with a bed of dense hairs that are a barrier to consumption of the leaf. But monarchs are patient, and have coevolved with the milkweed. So their first strategy is to shave that bed of hairs such that the caterpillar has access to the leaves that lie beneath.


For every defense there’s a counter defense. But next, when the monarch caterpillar sinks its mandibles into the milkweed leaf, it encounters a sticky, poisonous liquid called latex. In this video we will see how the monarch caterpillar deactivates the latex bomb that the milkweed puts forward.

And so the arms race continues, with reciprocal natural selection resulting in coevolution between monarchs and milkweeds. In my book, Monarchs and Milkweed, I outline the third level of defense and counter defense between these two enemies. Milkweed next mounts a remarkable and highly toxic defense chemical called a cardiac glycoside. But, yes, again the Monarch has evolved the means to not only not be poisoned by the cardiac glycoside, but to sequester it away and put it to work in defense of the Monarch itself from its enemies, such as predatory birds. For more on the Monarch – Milkweed arms race see this video, filmed in Ithaca, New York outside of Cornell University where we conduct our research.

AgrawalAnurag Agrawal is a professor in the Department of Ecology and Evolutionary Biology and the Department of Entomology at Cornell University. He is the author of Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution.

Anurag Agrawal: The oldest butterflies?

by Anurag Agrawal

It’s unclear when humans became humans. Presumably it was a gradual growth of our consciousness over the eons. There are some things, however, that appear to distinguish us from most other animals. For example, our artistic depictions. From the deepest, darkest caves have emerged pictures of humanity from thousands of years ago. And in an Egyptian tomb, that of Nebamun, on a painting called “Fowling in the marshes” (from around 1350 BCE) comes one of the oldest human depictions of butterflies. It happens to be of the African Monarch, Danaus chrysippus, sometimes called the plain tiger, a close relative of our beloved North American Monarch butterfly, Danaus plexippus.

I stumbled on this lovely scrap of history when a friend and colleague, Harry Greene, gifted me a book: Nabokov’s Butterflies (2000), a collection of unpublished and uncollected writings. Some explanation is in order. Harry is an extraordinary naturalist and big thinker in ecology and evolution. Like many senior scholars, his predicament was the lack of shelf-space in his office. And so I was the beneficiary of Nabokov’s Butterflies. Vladimir Nabokov, a Russian-American author, and noted entomologist, was most famous for his writings, for example, Lolita, and his celebrated translation of Pushkin’s novel in verse, Eugene Onegin. His ideas about biology were diverse, he was a passionate lepidopterist, and he often intermixed his literary writing and entomological excursions. Lolita is said to have been written primarily on butterfly collecting trips in the American west. Nonetheless, Nabokov also clung on to other ideas that held little merit in the scientific sphere. Most prominently, Nabokov rejected evolution by natural selection as a driver of certain organismal traits that he deemed ‘coincidental, miraculous, or too luxurious.’


Nabokov was a professor at my own Cornell University in the decade following WWII. Although he taught literature and had well-known students at Cornell (including U.S. supreme court justice, Ruth Bader Ginsburg), his entomological interests continued. In fact, after he retired from Cornell in the mid-1960s, Nabokov had sketched out an outline of a book: The Butterflies of Europe. And although the book never came to be, the outline was recapitulated in Nabokov’s Butterflies. Flipping through the book, I stumbled on his entry for Danaus in which he wrote, “This butterfly has the distinction of being the oldest known to have been represented by man. Seven specimens of it (with typical white-dotted Danaus body but somewhat Vanessa cardui like wingtips) are shown flitting over the papyrus swamp…” (page 603).

I later asked another friend, Harvard’s Lepidopterist, Naomi Pierce: did Nabokov have it right? On the money, she independently pointed to the similarity of Danaus chrysippus and the painted lady, Vanessa cardui, wondering if the butterflies on this three thousand year old tomb painting were Danaus or Vanessa. She concluded, as did Nabokov, that the African Monarch ruled. Detailed assessment of the color patterns on the wings were informative to both entomologists. The oldest human depiction of a butterfly? Perhaps not. Naomi mentioned some evidence of butterflies in Minoan artifacts from Crete, a thousand years earlier than Nebamun, and likely in Pyrenees cave paintings, some 10-30 thousand years earlier!

Of course, there is nothing special about being the oldest depiction of a butterfly by Homo sapiens. But suffice it to say, butterflies, metamorphosis, wing patterning, and the beauty of nature have been on our minds for a very long time. Thanks Harry and Naomi! And thanks Nabokov. Who knows what becomes of those side hobbies and obsessions we all hold.


AgrawalAnurag Agrawal is a professor in the Department of Ecology and Evolutionary Biology and the Department of Entomology at Cornell University. He is the author of Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution.

Anurag Agrawal: The migration patterns of the monarch butterfly

by Anurag Agrawal

The plight of monarch butterflies if often in the news: many scientists around the world are working hard to understand their annual migratory cycle. How do the monarchs produced during summer in the northern reaches of America contribute to the overwintering population in Mexico? The origin of monarch butterflies that make it to Mexico has been hotly debated because it has profound consequences for how we approach monarch conservation.

A new study is remarkable in its use of historical collections over the past 40 years and modern isotopic analysis. The scientists address the most important regions in the U.S. for producing monarch butterflies that actually make it to Mexico. This sort of data has been very difficult to come by and there has been a lot of speculation. As outlined in my new book from Princeton, the midwest has dominated discussions as being the most important region in the U.S. for monarchs. In the study, the authors find that the Midwest contributes a whopping 38% of the butterflies that make it to Mexico.


The regions studied by Flockhart et al. separated to highlight their relative areas

I would add two points for discussion. The first is that the areas of land that the authors designated as Midwest, Northeast, etc., seemed totally reasonable, but also somewhat arbitrary. In particular, an issue arises when you consider that, as designated in the paper, the Midwest is about 2.5 times as big as the Northeast. It is therefore not surprising that the Midwest produces about 2.5 times as many butterflies that make it to Mexico (38% vs 15%). In other words, the butterflies that make it to Mexico have about an equal probability of coming from the Midwest and the Northeast when land area is considered. Yet another way to think about this is that two states that are about equal sizes in the two regions (for example, Indiana and Maine) will on average produce about the same number of butterflies that make it to Mexico.


The annual migratory cycle of the monarch butterfly from Monarchs and Milkweed. In my past research, we have opted for a three simple regions defined by the butterfly generations.

Quite interestingly, the North Central area (including my home in the Finger Lakes region of NY) is slightly more important for butterfly production given its size. When you factor out the area of the Great Lakes (where there are no monarch caterpillars), the area of North Central is small (36% of the size of the Midwest). Thus, about 20% more butterflies per square mile come out of the North Central than the Midwest or Northeast. Where does this leave us?  The agricultural Midwest is certainly important, but perhaps not as important as previously thought.

The other point worth thinking about is that the Southwest (read: Texas) comes out as big in terms of area (equal to the Midwest) and relatively less important in terms of contributing butterflies (11% of the total).  The critical importance of the Gulf States including Texas, however, is not in the last generation of butterflies produced in fall that migrate south, but rather in the first generation of butterflies that are produced in spring and that migrate north to the Midwest and Northeast.  In other words, the Gulf States are absolutely critical for the annual migratory cycle, even if that is not where fall migrants are produced.  Without a spring generation there, the Midwest and Northeast would be empty!  In chapter 9 of the book, I summarize the critical importance of Gulf States not only for the spring, but also in providing floral resources for fall migrating butterflies.

I hope we see more studies like this in the future, as it provides new important information and was inspiring to read.

AgrawalAnurag Agrawal is a professor in the Department of Ecology and Evolutionary Biology and the Department of Entomology at Cornell University. He is the author of Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution.

Anurag Agrawal: Monarch overwintering

by Anurag Agrawal

The estimates of the monarch butterfly overwintering population were announced February 9th by WWF Mexico. The butterflies are so dense at their dozen or so mountain-top clustering sites that overwintering butterflies cannot be individually counted. Instead, the area of forest that is densely coated with butterflies (at about 5,000 butterflies per square meter looking up into the canopy) is estimated as a measure of monarch abundance. Butterflies arrive in Mexico around early November and stay until March.


This winter season (2016-2017), there were approximately 2.9 hectares of forest occupied with dense monarchs (somewhere in the neighborhood of 300,000 million overwintering butterflies). This estimate is down 27% compared to last year. Nonetheless, the previous two years were a 600% increase over the all-time low recorded in the winter of 2013-2014.


Where does this leave us? This year’s population was higher than predicted by many. The season started with a late spring storm that killed an estimated 5-10% of monarchs in March 2016, and many reported low numbers of adults last summer. Nonetheless, the lower numbers this season compared to last are within the range of year-to-year variation, and overall, the population seems to be relatively stable over the past decade. With these 24 years of data, there are various ways to plot and assess the trends. Below I have plotted the four year averages for six periods beginning in 1992. Any way you slice it, the trend has been negative, and the population is not nearly what it once was. Nonetheless, the downward trend seems to have lessened this last period. Is this the new norm? How dangerously low are these numbers? And what can we do to reverse the trend?


AgrawalAnurag Agrawal is a professor in the Department of Ecology and Evolutionary Biology and the Department of Entomology at Cornell University. He is the author of Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution.





Bird Fact Friday – Evolution

From page 14 of Better Birding:

Birds, like all animals, have evolved to take the best advantage of their environment. For example, the Northern Harrier glide and swoops low over fields and marshes, periodically flapping and hovering because that enables it to see the small rodents it preys on. Birds like wrens and rails are dark in plumage because they are most often found in dense habitats, the better to blend in with shadows. Species that make their home in the desert are often paler. The intuitive birder keeps these things in mind when looking for a specific species of bird out in the field.

Better Birding: Tips, Tools & Concepts for the Field
George L. Armistead and Brian L. Sullivan

Better BirdingBetter Birding reveals the techniques expert birders use to identify a wide array of bird species in the field—quickly and easily. Featuring hundreds of stunning photos and composite plates throughout, this book simplifies identification by organizing the birds you see into groupings and offering strategies specifically tailored to each group. Skill building focuses not just on traditional elements such as plumage, but also on creating a context around each bird, including habitat, behavior, and taxonomy—parts so integral to every bird’s identity but often glossed over by typical field guides. Critical background information is provided for each group, enabling you to approach bird identification with a wide-angle view, using your eyes, brain, and binoculars more strategically, resulting in a more organized approach to learning birds.