June Beetle Mob

It’s been a long week, so though I started a Friday 5, I’m not going to finish it before I fall asleep… Instead, I wanted to quickly share a video of some eastern green June beetles I encountered today as I walked past a bald cypress.  There was a lot of frantic buzzing going on, so I peered into the tree and saw this:

Apparently there was a shortage of female June bugs in the area as a good dozen males were flying around the immediate area and several males were attempting to mate with the one female in this video at one time.  I felt a little sorry for her, pursued by so many amorous males at once…

The June bugs appeared about two weeks later than usual here this year (that seems to be the case for many species in my area of North Carolina), but they seem more numerous than I’ve ever seen them too.  SO many Jung bugs flying around!  But I love it.  What gorgeous, fun animals.

I am going to try to get the post I started up tomorrow, but we’ll see if I get it finished.  Here’s hoping I’ll feel a little more energetic tomorrow!

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Unless otherwise stated, all text, images, and video are copyright © C. L. Goforth

Friday 5: Why Jumping Spiders Will Always Be My Favorite Spiders

I haven’t always been the biggest fan of spiders, but there’s one group that I’ve loved for as long as I can remember: the jumping spiders in the Salticidae family.  These charismatic spiders, sometimes called “salties” by their enthusiasts, are intelligent, expressive, interactive, and downright adorable compared to most spiders. But don’t take my word for it!  Today’s Friday 5 is all about convincing you all that salties are the best.

Reason Number One: The Eyes

Check  out the eyes on this little saltie, compliments of the magnificent Thomas Shahan:

Saltie eyes

Close up of the eyes of an adult female Paraphidippus aurantius. Photo by Thomas Shahan, used under Creative Commons. Original image available at http://www.flickr.com/photos/opoterser/4228767271/in/photostream/

Salties have very large eyes and are incredibly visual little spiders.   Their eyes are part of what give them their personalities as they are quite capable of and willing to follow you with their eyes – they can really watch you in a way most other spiders cannot.  (They’ll also interact with their reflections in camera lenses, which results in some of the really great head on shots of salties that you see around the web and among Shahan’s work.)  I think their ability to watch you and interact with you makes them seem a little less alien than many spiders – and much more palatable to more people.

Reason Number Two: The Hairdos!

Some salties have wild hairdos.  They can have little mohawks, beards, mustaches, spiky hair…  I think the hair makes these guys absolutely adorable!  I mean, how can anyone be scared of an animal, even a spider, with such ridiculous looking bedhead?:

Saltie hair

Hairdo of the female jumping spider Phidippus mystaceus. Photo by Thomas Shahan, used under Creative Commons. Original image available at http://www.flickr.com/photos/opoterser/6253069072/in/photostream

Fabulous!

Reason Number Three: Saltie Mating Dances

If you’ve never seen one of the saltie mating dances, you’re in for a treat today!  Researcher Jürgen Otto works with Australian peacock spiders and has captured some hilarious footage of their mating dances, including this:

SO funny!  I’ve watched this several times already and it makes me laugh every time.  Nature is so bizarre.  And awesome.  Completely awesome.

Reason Number Four: Peacock Jumping
Spiders Rock.  Enough Said.

The peacock spider in the previous video was pretty impressive, but they don’t hold a candle to this amazing, brilliantly colored beast, also recorded by Jürgen Otto:

Isn’t it great to live in a world where such crazy looking animals exist?  Peacock spiders alone would make me think that salties are the best spiders, even without  all the other crazy things they’ve got going on.  They’re just that cool.

Reason Number 5: They Are Amazing

I saw a TED talk a few weeks ago by Mark Berman about appreciating insects and their relatives.  I really enjoyed it, especially as promoting insect awareness and a greater love for insects is one of my personal goals.  It’s a bit longer and more academic than the other videos I’ve included here, but it’s well worth watching.  And why is it in my saltie Friday 5 post?  Because Berman uses salties as an example of an amazing arthropod – and has more hilarious video footage of saltie mating rituals to share:

I really love the quote at the end:

“The more moments in time you take to look again, the more amazed you’ll be by the world we live in.  But I suggest you shouldn’t be surprised.  You should come to get used to amazing things in your world.”

Couldn’t have said it better myself!  Love the salties and be amazed by them – but never be surprised by any of their fantastic and wonderful traits.

Go salties!

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Unless otherwise stated, all text, images, and video are copyright © C. L. Goforth

Science Sunday: Field Research vs. Lab Research

backswimmer

Backswimmer

I really enjoy field work.  Having grown up in an outdoorsy family, I spent a lot of time outside as a kid.  When it came time to choose a senior thesis topic in college, I headed straight for the local wetlands, plopped myself down on a boardwalk, and watched damselflies flying around for several weeks.  I swore to myself that I was going to do all of my graduate research outdoors because that’s what I loved to do.

My regular readers know that plan didn’t quite pan out (click here for examples).  But there’s a reason for that!   There are times when it’s easier do work in the lab and there are questions that are nigh impossible to answer in the field.  So, today I’d like to do something a little different for Science Sunday.  Instead of discussing an article about research, I’m going to discuss a few (very few) of the pros and cons of working in the field versus the lab.  For the scientists out there: you probably know all this already, so thanks for stopping by.  But for those of you who aren’t scientists, this might give you some insight into how scientists plan their experiments and the research decisions they make.

Let’s start with a hypothetical question, something that you might find me doing: do the behaviors of backswimmers (pictured above) allow them to use the air bubble they carry on the underside of their abdomens as physical gills so they can extract oxygen from the water?  Now, there are several different ways I can approach this question, so let’s consider some pros and cons of doing this sort of study in the field.

Field Work

PRO: You are able to observe the bugs in their natural surroundings.

When you’re dealing with behavioral questions, you can often make the best observations in the field.  In our hypothetical scenario, the bugs are going to be much happier, and therefore much more apt to behave as they do normally, if you observe them in the field.  As an observer, you will cause a certain level of distraction that might interfere with their normal behaviors to some extent, but it’s certainly going to be far less than what you’re going to get by scooping the bugs out, driving them back to the lab, and dumping them into containers.  When possible, it’s great to do behavioral studies in the field for this reason.  However, that’s not always possible because…

Con: You have no control over the conditions

To be able to say that X causes Y, you need to do a carefully controlled experiment where all the variables are accounted for.  It’s possible to do experiments in the field, but there are a lot more variables that you have to take into account.  For example, let’s say you’re doing a field experiment with the backswimmers.  However, it turns out that one set of treatments was applied to bugs in the middle of the stream and another to bugs closer to the shore.  If you compare the treatments and observe differences, you can’t ever be completely sure that you know why they’re different.  Your treatments likely had an effect, but what about the differences in flow between the two areas (faster in the middle, slower closer to shore)?  The increased energy demands of swimming in the middle of the stream relative to the areas closer to shore?  The different oxygen levels in the two areas?  Taking your experiment into the lab ensures that the only difference between the two treatments is the treatment itself so you can say that your treatment caused the observed outcome.  You probably also want some field observations when possible so that you provide evidence that your lab experiments didn’t affect the behaviors (e.g. did you know that female mantids don’t normally eat their mates and only do that in the lab?), but this isn’t always possible.

LabLab Work

Working in the lab has benefits, but it’s not always the ideal place to work.  Apart from being able to precisely control your experiments at the cost of removing things from their natural environment, the pros and cons of lab work include:

Pro: Greater access to a wider variety of Research tools and equipment

There are some things that are difficult or impossible to do in the field.  For example, let’s say you want to measure the oxygen in the air bubble that the backswimmer carries with it in the water.  That involves using some expensive precision equipment with specific power and space requirements that are hard to replicate in the field.  You might want to use a microelectrode to measure the oxygen level of the bubble.  Microelectrodes break very easily, so dropping one into the stream or on the ground would be a terrible thing – $5000 down the drain!  You wouldn’t be able to use the stands or the micromanipulators in the field that make using the electrodes easy in the lab.  It’s certainly not ideal to take the computers and analyzers you need to record the data out to the field.  Microelectrode oxygen readings also change depending on the temperature, which is impossible to control in the field.  If you need any sort of fancy equipment, it’s often better to do your experiments in the lab.

Con: Space can be an issue

Working with insects is great because you rarely need a lot space to do your experiments.  For the hypothetical backswimmer scenario, a small lab (heck – a table!) has ample space to do a behavioral study.  But what if you’re working with deer or leopards or bald eagles?  You’re certainly going to have a much harder time bringing them into the lab, nor could you expect their behavior to be normal indoors.  In fact, you’ll probably have to sedate them to get them into the lab in the first place and then house them in small cages while they’re there to do anything with them.  If you’re planning to measure hormones in blood or are interested in body measurements, then this sort of thing is ideal.  If you want to study behavior…  Not so much!  You’ll get better results in the great wide outdoors than you ever will in a lab.

These are the sorts of things all biologists wrestle with when they decide how to answer their research questions.  You have to carefully weigh the pros and cons of any particular experimental design and choose the one that’s most likely to produce reliable results.  Sometimes it’s better to do your work entirely in the field or entirely in the lab, but other studies (like mine!) lend themselves well to doing both.  And thank goodness for that!  I wouldn’t want to spend all my time indoors.  :)

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Unless otherwise stated, all text, images, and video are copyright © TheDragonflyWoman.com

Well-Nigh Wordless Wednesday: Puddler

I love it when I walk out my front door and see this sort of thing going on in the parking lot:

puddling butterfly

Giant swallowtail puddling

The irrigation system in my housing complex breaks all the time, so we end up with little puddles all over the parking lot that attract butterflies.  Butterflies, such as this giant swallowtail, have a hard time getting enough salt and minerals in their diets, so they “puddle” – they suck up moisture from damp areas rich in the nutrients they need.  Apparently we have a salty parking lot because butterflies LOVE it!  And I love photographing them, so I consider it a win-win situation.

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Unless otherwise stated, all text, images, and video are copyright © TheDragonflyWoman.com

Friday 5: Fun Facts About Giant Water Bugs

This week’s Friday 5 features a subject near and dear to my heart: giant water bugs!  If you aren’t familiar with these beasts, they have some really amazing characteristics that make them a fascinating group of insects to study.  I’ve already covered giant water bug parental care and feeding in other posts.  Today I’m going to share 5 fun facts about giant water bugs.  I hope that knowing these facts will help you fall in love with these wonderful bugs!

Lethocerus medius

Lethocerus medius, the biggest giant water bug in Arizona, can reach lengths of nearly 2.5 inches!

1.  The largest true bug (i.e. member of the insect order Hemiptera) in the world is a giant water bug.

Lethocerus maximus is truly a giant, reaching nearly 5 inches in length!  However, if you want to add one to your collection, you’ll have to visit northern South America.  The Lethocerus in the US are piddly in comparison, topping out at about 2.5 inches – half the size of the biggest species.

Abedus cannibalizing eggs

A male Abedus herberti cannibalizing his own offspring after he scraped them off his back.

2.  Giant water bugs can be cannibalistic.

A hungry giant water bug will eat almost anything it can get its claws on, including its own young (only when very hungry or something has gone wrong with the eggs a male is caring for), the young of other individuals, and each other.  Female Lethocerus are also known to rip apart the egg clutches deposited by other females when there aren’t enough males with good egg laying sites to go round.  However, I haven’t observed giant water bugs eating each other in the field unless there is very little other food available and they are getting desperate.  It would seem they prefer not to eat each other, but they will when they have no other choice.

Abedus herberti mating

Abedus herberti mating.

3.  Giant water bug mating can take several hours, especially in the back brooding species.

Mating is a long, involved process in the back brooding giant water bugs.  First the male does little push ups in the water.  These are thought to send vibrations through the water that the females respond to.  After a male and a female find one another, they mate.  Then the female climbs on the back of the male and lays a few eggs, maybe 4.  Then the male shakes her off and they mate again.  Then she lays a few more eggs before being shaken off again.  This goes on and on until most of the back of the male is covered with eggs, sometimes 150 altogether!  You can see how this might take a long time.  The water bugs in the photo took over 6 hours to lay all of their eggs.

Belostoma micantulum

Belostoma micantulum, a giant water bug from Argentina, is one of the smallest giant water bugs in the world.

4.  Not all giant water bugs are giant.

Belostoma parvum, a giant water bug from northern South America, can be less than a centimeter long.  It’s a not-so-giant water bug!  In fact, several species of giant water bugs in the genus Belostoma are actually quite small and don’t live up to the “giant” in their name at all.  The giant water bug pictured here is Belsotoma micantulum, a tiny little giant water bug that maxes out at a little over a half an inch long.  Pretty cute though, especially when munching on a mealworm that is WAY too big for her!  :)

flood

The only flash flood I've ever personally witnessed, though it's hard to see how big this flood was in this photo! Clicking on the photo will take you to a cruddy, low-res video I shot of it and posted on YouTube.

5.  At least one species has a nifty flood-avoidance behavior.  

Imagine you’re an aquatic insect and a flash flood is headed your way.  You’re going to be ground into a bloody pulp if you stick around.  What do you do?  If you’re the giant water bug Abedus herberti, you climb out of the stream before it floods!  This species crawls out of the water and walks perpendicularly to the bank until it reaches shelter away from the stream.  After the flood passes through, it crawls back into the water and carries on with its regular activities.  Awesome behavior!  And you can see a video of it online by visiting Dr. Dave Lytle’s website.  He filmed Abedus herberti leaving the stream after artificially simulating flood conditions with a fire hose.  The video is hilarious, so I encourage you to take 30 seconds out of your day to watch it.

Aren’t giant water bugs cool?  I love my bugs.  Considering they mostly just sit in one place hoping that food will swim by, it never ceases to amaze me just how many wild characteristics these bugs really have.  Hope you enjoyed this little peek into some of the many fascinating things these bugs have going for them!

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Unless otherwise stated, all text, images, and video are copyright © TheDragonflyWoman.com

Weather and Odonate Behavior

Anax junius in flightI’m running a little behind this week, but it’s a new year and I think it’s time to discuss my favorite scientific topic in the world: odonate behavioral responses to weather!  I have been interested in dragonflies for a long time, almost as long as I’ve been interested in insects.  I think they’re beautiful, amazing animals and I am in complete awe of them for many reasons.  When I was an undergrad, I took an ecology class in which we were required to do a personal project, so I naturally gravitated toward dragonflies.  That project turned into a senior thesis for my biology B.A. and eventually became the basis for a scientific paper.  I’ll talk about the results of my study next week.  Today I want focus on what’s known about the behavioral responses of odonates to weather, observations by other scientists who have inspired my work in this field.

As most of you reading this will know, dragonflies are powerful fliers.  However, they still have limitations.  They have massive, broad, flat wings and though they have bulky bodies, they just don’t weigh that much.  So, imagine you’re a dragonfly.  It’s a nice sunny day, but a storm is moving in.  It starts to get cooler, darker, windy.  Are you, as a light-bodied animal with gigantic wings, going to keep flying as the weather deteriorates?

If you answered no, you’re spot on!  Dragonflies and damselflies are known to be strongly affected by changes in weather.   Changes in weather throughout the day can have a significant impact on how a population of odonates behaves.  In fact, weather plays such a huge role in odonate behavior that you see some variation on this sentence in countless scientific papers:

“Data from days exhibiting inclement weather were removed from the data set before analysis.”

There’s a reason so many people do this though.  Though very few researchers have looked specifically at the role weather plays in shaping odonate behavior, these insects are well-known to behave strangely under certain conditions.  If your study is looking at, say, patrolling behaviors in a dragonfly species and a change in weather occurs that disrupts their normal behavior, that data really doesn’t help answer the questions you’re interested in.  You therefore remove that data before you analyze your results because it is not related to your study.  And ultimately, even scientists don’t like to stay outside when it’s rainy, cold, very windy, or otherwise unpleasant.  Scientists just miss a lot of what happens during those inclement weather days.  That’s unfortunate because that’s when some of the most interesting things happen!

Snowman

Snowman from one of our aquatic entomology field trips. Dragonflies would not fly in this weather! Photo by Dennis Suhre.

So what do we know about odonate responses to weather?  Several things.  Let’s consider temperature first.  Odonates are exothermic, like all insects.  If they get too cold, they can’t warm their bodies up enough to fly.  If they get too hot, all kinds of nasty chemical reactions start taking place in their bodies that can result in death if they become severely overheated.  (Long ago, I posted about obelisking behavior in dragonflies, a behavior that helps dragonflies cool down on hot days.)  Changes in temperature are known to influence odonate behavior such as the time of day that a species normally flies, flight activity levels throughout the day, and the postures of dragonflies.

Wind and a palm tree

A palm tree on a windy day.

Wind also plays a role in odonate behavior.  On very windy days, damselflies won’t fly at all, or only in places that are protected from the wind by barriers of some sort.  Dragonflies are able to fly in stronger winds, but even these larger insects have their limits and must stop flying if the winds become too powerful.  Light intensity hasn’t been looked at in as much detail as wind, but it is known to impact fight activity as well.  Activity levels tend to go up and down with light intensity.  More odonates tend to fly on sunny days than on cloudy days.

These are the obvious weather factors.  You can easily observe an increase in wind speed, a drop in the light levels, or a drop in temperature.  What about the less obvious changes in weather like barometric pressure and relative humidity?  Relative humidity isn’t considered by most researchers, so there is very little data available on its effects.  However, one Russian scientist in the 60’s published a paper proposing a link between barometric pressure and dragonfly behavior.  I happen to disagree with him, but I’ll talk about my reasons when I discuss my own study next time.

The Catalina Mountains as a storm rolls in

The Catalina Mountains as a storm rolls in.

Finally, let’s consider rain.  Glorious rain, my favorite weather!  Damselflies almost never fly in the rain.  Some of their larger dragonfly relatives have been observed flying during rain (including my favorite magnificent flier, the wandering glider), but few reports have been made of any dragonflies flying during heavy rains.  In fact, several researchers have observed that dragonflies and damselflies essentially disappear from the water’s edge right before it starts to rain.  This behavior has been named pond abandonment behavior, and it is this behavior that I am most interested in.  Why are they leaving?  Where do they go?  Are they using cues from their environment to tell them when to leave the pond and when to return?  This behavior is fascinating!

This is the sort of information I had to go on when I started my project looking at dragonfly behavioral responses to weather as an undergrad.  The few researchers that have examined the role weather plays in odonate behavior tended to analyze each weather factor separately, sometimes using data from different days.  If you’ve ever watched a storm rolling in, you know that light intensity rarely changes without a change in temperature and the wind often increases before it starts to rain.  Weather factors are clearly linked.  And most of the time you’re not lucky enough to find studies that overtly link weather and behavior to begin with.  The information about this topic tends to be hidden in papers about completely unrelated subjects, often preceded by one of those, “Data from days exhibiting inclement weather…” statements.  I happen across most information about odonates and weather when I’m reading about territoriality or dragonflies using sunny spots in forests as hunting areas.  Lots of odonate researchers know that weather plays a role in odonate behavior (a significant role in fact!), but figuring out exactly how weather does this…  Well, that’s what I am interested in figuring out!

Next up is another Friday 5, but my post early next week will focus on the things I’ve learned in my own work with odonates and weather.  This has been my pet topic ever since that first little study I did in my first ecology class in college – I love this subject!  I hope you’ll enjoy it too!

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Unless otherwise stated, all text, images, and video are copyright © 2011 DragonflyWoman.wordpress.com

Using publicly collected data to study dragonfly swarms: Part 3

Before I get to the buggy stuff today, I’d like to extend a hearty thanks to WordPress for selecting my post on Arizona’s beetles for Freshly Pressed!  It was an unbelievable honor and I am so very thrilled to have been chosen.  The publicity resulted in a bunch of new subscribers to my blog, so I want to give a warm welcome to all of you who recently subscribed!  I hope you like what I have to offer.  And to my subscribers who’ve stuck around for a while, thank you so much for your continued support.  The blogging experience is so much more fun when you have the opportunity to interact with your readers, so a big thank you to all of my readers for injecting an extra little dose of joy into my life!

dragonfly swarm banner

Well, most of the dragonflies that going to migrate in the U.S. already have and many of those left behind are nearing the end of their lifespans.  This will therefore be the last of my posts on dragonfly swarming behavior this season!  As promised, today I’ll be making some conclusions about dragonfly swarming behavior from the data that I collected from my readers this summer.  Making conclusions of this sort is ultimately what we biologists strive to do: we try to explain something extraordinary about our world using the evidence we gather via our research.  In this case, my research involved several hundred people from all over the US, Canada, Belize, India, and Mexico, and it’s a lot of fun to go through the data!

Considering I have enough data to write a full-length scientific paper on this topic,  I could write the mother of all blog posts.  But you all don’t want to listen to me ramble on and on and on about this.  (Just ask my husband!  He bore the full brunt of my obsession with this project over the summer!)  Instead, I’ll limit myself to discussing three main conclusions to keep it a decent length.

Conclusion 1: Dragonfly swarms, both migratory and static, are more common in the midwestern and eastern US than they are in the west.

There are several reasons why this might be, but the most obvious explanation is that we just don’t have as much water in my third of the country as the areas where the major swarms took place this summer.  The majority of the reports I received were from areas that had major bodies of water within 10 miles, especially rivers.  Dragonflies are thought to use landscape features for navigation during migratory flights, and indeed most of the migratory swarms reported occurred along major rivers, lakes, or coastlines.  Static swarms also occurred more frequently in areas with a lot of water than in more arid regions.  So, the more water nearby, the more swarming activity an area had.

I think there are two reasons why water in an area would lead to increased swarming activity.  For one, dragonflies are aquatic insects.  They find mates near water, lay their eggs in water, and their offspring spend the majority of their long lives in water.  It stands to reason that areas with lots of water might therefore also have a lot of dragonflies.  And lots of dragonflies means that swarming behavior should be more common, or at least more obvious to human observers because more individuals will be nearby and able to participate.  However, consider also why static swarms form: dragonflies are attracted to locally abundant, swarming prey.  Dragonflies love to eat  insects such as mosquitoes, non-biting midges, and biting midges.  And where you get big swarms of these insects?  Near water!

I think water plays a big role in shaping the distribution of dragonflies in North America.  Take another look at the swarm map video I posted last time if you want to confirm this for yourself.  Notice how many swarms were reported near the Great Lakes, along the Mississippi River, along the Missouri River.  Then take a look at the west, where we just don’t have many big rivers and two of our biggest lakes are saltier than the ocean.  I’ll have to do some fancy analyses to properly test this idea statistically, but my preliminary data suggests that water availability largely explains the patterns in dragonfly swarm distribution reported across North America.

Conclusion 2: Dragonfly swarms are closely tied to weather patterns.

As someone whose pet research project has long been determining the impacts of weather on odonate behavior (I just had a paper published on this topic and I’ll be posting about it soon!), I was overjoyed to learn that weather plays a major role in shaping dragonfly swarming behaviors.  Migratory swarms, as observed by other researchers, usually occured after cold fronts move through an area.  Indeed, in nearly all of the migratory swarm reports I received, the reporter mentioned that it had become dramatically cooler in the area 12-48 hours prior or that a cold front was due to arrive soon after.  My data further suggest that migratory swarms may occur just before major storms hit an area.  The static swarms were also mostly weather related, typically occurring just before or just after storms.

There are tons of things coming into play here, but here’s what I think is happening.  Storms are known to assist in moving dragonflies over long distances (especially the migratory species)  and some species have been observed feeding more heavily just prior to and after storms.  This means that there are more dragonflies in an area that is about to be hit with a storm or just after a storm passes and they’re eagerly looking for things to eat.  Any small swarming prey insects that happen to come out at that time, especially in response to the storm, are going to attract dragonflies and cause static swarms to form.  Storms might also prompt many dragonflies to move from one area to another, using the wind generated by the storm to assist in their dispersal, especially in areas where the density of the dragonflies is very high.  This could be the reason that I had so many reports of migratory swarms that occurred along with storm activity rather than cold fronts.

Weather likely impacts dragonfly swarming behavior directly in these ways, but there are also indirect effects.  Heavy storm activity in an area can cause major changes in the aquatic landscape and these changes have a direct impact on many dragonfly prey species.  Mosquitoes are especially adept at utilizing new and temporary bodies of water and populations of the flies can explode following major storm events.  Increases in mosquito populations promote increases in dragonfly populations as well: more food means more dragonflies are able to live in the area.  In many areas where major swarming activity was reported this summer, significant flooding also occurred days or weeks before the swarming began.  For example, Milwaukee  was bombarded by storms this summer and I’m told many areas of the region flooded.  Mosquito populations skyrocketed in response to the flooding, and then the dragonflies started forming massive static swarms over an enormous area of Wisconsin.  It looks as though storms cause spikes in dragonfly swarming activity in general, but areas that experience major flooding are especially likely to see a massive increase in dragonfly swarming.

Conclusion 3: 2010 was a special year for dragonfly swarms.

Although I know from personal experience that it’s uncommon to see dragonfly swarms, I was quite shocked that about 98% of reporters told me that they had never seen anything like what they’d witnessed before.  Though I say this tentatively because I don’t have enough data to truly support this idea, I believe that 2010 was an extraordinary year for dragonflies in the midwest.  A perfect combination of events seems to have occurred that allowed the dragonfly population to explode.

Let’s take a moment to consider just how many events had to fall into place to allow so very many dragonflies to make an appearance this summer!  Dragonflies often spend over a year in the water as nymphs, so 2010’s dragonfly swarming boom probably began 1-3 years ago.  Conditions in the water had to be just right to allow millions or billions of dragonfly nymphs to survive to adulthood.  This means that the dragonflies likely experienced mild conditions during the winters, the water quality was decent, and that there was abundant prey available for them to eat.  Once the millions or billions of dragonflies emerged from the water and molted into adults, they all required food for continued survival.  Luck was on their side this year as major flooding occurred in several parts of the northern midwest, driving mosquito and midge populations up to abnormally high levels.  Swarming flies attracted dragonflies, so dragonfly swarms formed very often.  I think that this combination of factors, high nymphal survival followed by an overabundance of prey, caused the explosion of dragonflies observed in the midwest this year.  The response of the incredibly high number of dragonflies to the highly abundant prey then in turn led to a much greater than normal level of swarming behavior.

I think that this perfect combination of events probably occurs rarely.  How else do you explain the number of people who said they had never seen anything like it before, the number of reports on television news programs, the number of scientists in the midwest trying to allay the fears of the populace as millions of dragonflies descended on their homes?  That said, I still have 2 questions.  The first: is this really an extraordinary event or does it just seem that way from the reports?  For those of you who are familiar with statistics, my n=1 summer, so I won’t really know the answer to this question until I collect data for a few more years.  The second: how is climate change going to impact this behavior?  If global warming occurs, you might expect to see warmer, milder winters that support explosive populations of dragonflies like the ones witnessed this year, making these sorts of summer more common.  On the other hand, recent studies suggest that the midwest might have colder, more severe winters as climate change occurs, so fewer dragonflies may survive through the winter in the future.  In essence, I need more data collected over more time to begin to answer these questions.  I intend for this to become a long-term research project, one that may occupy a part of my summers for many years to come, so hopefully I’ll have some better answers in the future.

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Have you seen a dragonfly swarm?

I am tracking swarms so I can learn more about this interesting behavior.  If you see one, I’d love to hear from you!  Please visit my Report a Dragonfly Swarm page to fill out the official report form.  It only takes a few minutes!

Thanks!

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