Dragonfly Swarms Revisited

Pantala flavescens

A wandering glider (Pantala flavescens) from the swarm I witnessed last summer.

Since I put out my request for reports of dragonfly swarm sightings a month ago, data have been streaming in!  I thought it was time to give a brief report of the dragonfly swarming activity in North America this summer so that everyone who’s sent a report in can see how much I appreciate your sending me reports.  I couldn’t be happier with the information that’s been coming my way, so thank you all so much for helping me track this behavior.  Keep the reports coming!

First things first.  In my next post, I’m going to cover a paper I came across on dragonfly migratory swarms in North  America from 1998.  I think it will give everyone a better idea of why these swarms might be forming and what they’re doing.  For now, just know that there are two types of swarming behavior:

  1. Migratory swarms. These are effectively rivers of hundreds of thousands of dragonflies all flying in a single direction and covering large distances.  These types of swarms are like bird migrations or the migrations of monarch butterflies – lots of individuals traveling together between habitats and usually made up of a single species or with one dominant species and a few other minor players.  These swarms move very quickly and may appear and disappear in a matter of minutes.  The dragonflies in these swarms typically follow significant waterways and fly high above the ground (20-100 feet).
  2. Static swarms. This is the type of swarm I reported on last summer and the type that prompted my interest in this behavior.  These swarms contain far fewer individuals than migratory swarms (20-1000 instead of tens of hundreds of thousands) and are highly localized.  Individuals in the swarm will remain restricted to a very small area (like one field or yard or hill) and fly in a circular or figure-8 pattern about 1-20 feet off the ground, usually over a grassy area.  These swarms are likely feeding swarms and may contain one to several species of dragonflies in about equal proportions.  (Please read the post from last summer linked above for a more detailed description of the behavior of the swarm I witnessed and a video.)

These two types of swarms, though very different, might be related to one another.  There are some striking similarities between the two types that suggest that this might be the case.  For one, the known migratory dragonfly species are the same species that appear to be making up the static swarms.  Also, both types of swarms occur during the same part of the year.  Last, both types of swarms seem to be weather related.  Almost everyone who has reported a swarm has also reported a recent storm or an incoming one, especially after a long period of hot, dry weather.  Weather is thought to play an important role in the migratory swarms as well.

When I wrote my initial posts on dragonfly swarms, I got a few reports from people who had seen them in other locations.  I also got several people stumbling onto my blog after searching for dragonfly swarms on the internet.  Last summer I got maybe 30 hits a week on my swarm pages and none at all for most of the rest of the year.  This year, I’m getting 500 hits a week!  Clearly, something is happening this summer that is making these swarms much more abundant and visible than they have been in the past.  I can’t, of course, say for sure why this is, but I suspect it has something to do with the weather pattens we’ve seen this year.  I saw a report on the National Geographic website a few days ago that said that this is the hottest year on record in the US – and we started recording weather data in the late 1800’s.  Perhaps the hot weather and the recent rains have something to do with the huge number of swarms (and the large size of some of these swarms) that have cropped up this year.

So what patterns have I been able to identify from the data I’ve collected from reports from readers?  There are definitely a few locations that have a lot of static swarming activity recently:

  • Eastern Missouri in the St. Louis area.  There seem to be many swarms within a massive area from slightly north of St. Louis south to the MO border and extending west to the central part of the state.  These swarms are highly localized when they appear and are often in one person’s yard or field and not in the yard/field next door.  The swarms have been made up of several different species and consist of several hundred dragonflies.  It has been quite hot in the area, but they’ve had some recent storms.
  • Northern Illinois/Wisconsin.  These swarms may be part of the Missouri action because they are very similar.  They also cover a large area, consist of mixed-species in highly localized areas, and they’ve been showing up after storms.  It’s been hot in this area recently too.
  • New Jersey.  These sightings seem to be completely unrelated to the swarms in the Midwest, but they’re spread across the state.  The swarms are a bit smaller than the Midwestern ones (20-100 individuals), but they’re often made up of multiple species and have appeared before or after storms.
Pantala hymenaea banking

A spot wing glider (Pantala hymenaea) from the Tucson swarm last summer.

Other sporadic swarms have been reported in Iowa, Ohio, Texas, Tennessee, New York, Connecticut, California, Pennsylvania, and Saskatchewan.

Based on the data I’ve collected so far, it looks likely that in many areas, there are very large, widespread groups of dragonflies.  The swarms people are seeing in their yards may be a subset of these larger super-swarms.  I’m starting to think this because I’ll get 20 different reports from one rather large geographic area all describing the exact same thing over the course of 3 or 4 days.  I’ll get another 20 reports from another area, all with similar descriptions and within a few days of each other.

I did also get several individual reports of a massive migratory swarm in downtown Little Rock, Arkansas earlier this week.  The accounts I heard suggest that the swarm was made up of truly staggering numbers of dragonflies, maybe hundreds of thousands or millions of individuals, that all flew right by the 6th floor windows of several buildings.  One reporter said he couldn’t see the building across the street as the dragonflies flew by!  They were all flying parallel to the river and in a single direction and the whole event was over in less than a minute.  Wow.  I would have given anything to see that!  If anyone else is lucky enough to witness an event like this, I hope you will send a report to me!  However, though I got many reports of this single event, they’re the only reports of anything like migratory swarms I’ve gotten all summer.  It appears that the static swarms are much more common than the big migratory swarms, but I think there’s a good chance that they’re related to one another.

And this is where you all come in!  Keep sending me your reports!  With your help, I might be able to get a better handle on the movements of my proposed super-swarms and determine whether the migratory and static swarms are actually related.  I might also be able to determine whether the Midwestern swarms are all part of one giant swarm or the Missouri and Illinois/Wisconsin swarms are separate.  Plus, I have a feeling this is a special year for this behavior and we might never see another summer like this again.  I’d like to collect as much data as I can now so that I can compare this year to future years and to take advantage of the abundance of swarms that are cropping up throughout the country.

Check back soon for the summary of the migratory swarm behavior paper!  Judging from the number of people who have been searching for information on dragonfly swarms on the internet this summer, it might be quite interesting for people hoping to explain the phenomena they’ve been seeing in their backyards.

(Want more information about dragonfly swarms?  Visit my Dragonfly Swarm Information page for my entire collection of posts on dragonfly swarms!)

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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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Want more information?

Visit my dragonfly swarm information page for my entire collection of posts about dragonfly swarms!

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

Unless otherwise stated, all text, images, and video are copyright © 2010 DragonflyWoman.
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Entomophagy for a Healthier Planet

A few weeks ago I wrote about my distaste for eating insects.  At the end, I included a poll to determine whether my readers agreed with me or not.  Apparently they don’t!  The results looked like this:

bug eating graph

Percent of people willing to eat bugs, would not eat bugs, or might eat a bug under certain conditions.

I have to admit that I was a little surprised by this results.  Seriously?  64.3% of people would be willing to eat an insect?  Then I considered my audience.  The majority of readers of my blog are a) entomologists by vocation or avocation, b) naturalists by vocation or avocation, or c) interested in insects enough that they were able to find my blog.  People who study bugs (or just really like them) are admittedly more likely to willingly eat an insect than people who do not.  In my experience, people who love nature are more adventurous than the average person you encounter on the street, which also makes them more likely to eat an insect than the rest of Americans.  So, it shouldn’t be a surprise to me that 78.6% of people polled would be willing to eat an insect under at least some condition.  Apparently my anti-entomophagy stance  in the minority.  I’m comfortable with that.

Dr. Marcel Dicke of the Wageningen University in the Netherlands might find the results of my poll encouraging.  Dr. Dicke recently gave a talk at the TED Global conference in Oxford about the importance of insects for human consumption.  As an entomologist, he is trying to convince people that insects are nutritious and something that we need to consider eating if humans are going to continue to eat animals as food.

eating insects

Dr. Marcel Dicke offers insects to the TEDxAmsterdam host. Photo taken from http://www.tedxamsterdam.com/2010/marcel-dicke-and-the-critters-that-go-‘crunch’/.

Dr.  Dicke’s talk hasn’t been made available on the TED Global conference website yet, but his talk was chosen for the conference after he gave a similar talk at the TedxAmsterdam conference last year.  I highly recommend that everyone watch the 16 minute video!  During his presentation, he discussed the importance of insects in the world economy, their abundance and diversity, and the services that insects provide for humans.  He also briefly covered how many insects we already consume without knowing it.  He mentioned the limits the US limits of insect parts determined and regulated by the FDA.  We eat a LOT of insects every year without our knowledge (Dr. Dicke says it’s 500 grams, or a little over 1 pound, per year!).  The cochineal bug is even used as a natural red food dye.  Next time you buy something red, look for Red E120, carmine, or Natural Red 4 in the ingredients and you’ll know you’re eating an extract made up of mashed insects!  Dr. Dicke said that cochineal dye is a great moneymaker too: 1 gram of cochineal sells for 30 Euros.  In contrast, 1 gram of gold goes for 25 Euros.

Dr. Dicke strongly believes that humans should eat more insects.  In his talk, he stated that 70% of the world’s population already happily eats insects.  Humans currently eat over 1400 different species of insects and they are considered a delicacy in many regions where they are regularly consumed.  If this is the case, there isn’t any reason why Europeans and North Americans shouldn’t be eating them too.  Dr. Dicke suggests that it’s all a matter of perception.  In Europe and North America, we are taught that insects are gross, so we don’t have the proper mindset to consume insects.  But, he also said that this might have to change.

The world’s population is expected to increase by 1/3 over the next 40 years.  By 2050, we might have 9 billion people on Earth.  This increase in human population means that we have to increase our food production to keep up.  In fact, projections suggest that with that 1/3 population increase, our food consumption will increase by 70%!  This figure apparently takes into account the expected increase in quality of life in second and third world countries, which would translate into increased food consumption even if the population remained the same.  All in all, we humans are going to need a LOT more food to survive.  But what should we eat?

Dr.  Dicke stated that animal proteins are a valuable part of our human diet.  However, this introduces a problem: just how much further can we increase livestock production?  Dr.  Dicke said that we’ve nearly maxed out our livestock production already and that this form of protein production isn’t going to be sufficient to feed all of those extra people on the horizon.  Even if we chop down all of our forests, we’re still going to need more space for livestock than is available if we’re going to feed 9 billion people.  So where do we turn?  To insects of course!

Dr. Dicke believes that we will have to start eating insects if we are going to continue to consume animal protein in the future.  He also thinks this is a great idea.  He outlined 4 reasons why we should eat insects instead of the livestock animals we currently consume:

  1. Insects are distantly related to humans.  Livestock animals are much more closely related to us than insects are, which means that they can transmit diseases to us when we grow or eat them.  Insects don’t have any known diseases they transmit to humans when we eat them, so they are a safer source of food.
  2. Insects utilize their feed much more efficiently than livestock animals.    Animals don’t use every bit of the food they eat.  Some animals process a lot more of their food than others though.  Dr. Dicke said that for every 10kg of feed, you get 1kg of cow, 3kg of pig, 5kg of chicken, and 9kg of insects.  Clearly insects give you the biggest bang for your buck.
  3. Insect wastes are less harmful to the environment than livestock wastes.  Insects produce far less waste than livestock animals, but they also produce less toxic wastes.  Livestock animal waste is full of nasty compounds like ammonia and methane that harm the environment.  Eating insects would reduce the cost of animal protein production on our planet significantly.
  4. The nutritional value of insects is excellent.  They’re full of high quality protein, have a reasonable amount of fat, and provide serious calories.  According to Dr. Dicke, one kilogram of grasshoppers is equivalent to 10 hot dogs or 6 Big Macs!

Dr. Dicke is trying to convince people in Europe and North America that they need to shift their perception of insects away from gross things that should be avoided to something that is a valuable food source.  He doesn’t think this should be hard.  After all, people in these countries already eat shrimp, and, according to Dr. Dicke, “Insects are just the shrimp of the land.”  He suggests that insects might first need to be hidden in foods and that this might start happening over the next few years.  He predicts that in 10 years, we will be openly eating insects as part of our regular diet and won’t need to hide them any longer.  I personally think this estimate might be a little optimistic (have any of you ever asked an average American if they’re willing to eat an insect?  The look of revulsion on their faces speaks volumes!), but I think he’s right.  Insects ARE the best thing we can produce as an animal food source.  There are so many good reasons to eat insects.  And this, a snack provided at both the TEDxAmsterdam and TED  Global conferences, should be one of them:

insect and chocolate covered strawberries

Mealworm and chocolate covered strawberries. Photo taken from http://www.tedxamsterdam.com/2010/marcel-dicke-and-the-critters-that-go-‘crunch’/.

Yum!   Even I might be inclined to try one of these…

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Click! Click! Click!

In the summer months in Arizona, it’s common for things to come crawling into your house to avoid the heat.  Leave a door open and your house will soon be full of mosquitoes, geckos, several types of beetles, webspinners (which are insects and NOT spiders), green lacewings, sun spiders (also not spiders), moths, maybe even the occasional bark scorpion or snake.  I happen to have a dog door that doesn’t quite close all the way due to the pressure built up by the evaporative cooler, so all kinds of insectoid creatures make their way into the house that way.  My personal favorites of the things that end up in my house are these:

click beetle

Click beetle, likely Melanotus sp.

Click beetles!  If you haven’t ever gotten to play with a click beetle (and let’s face it – most people don’t squeal with delight and immediately put their hands on random beetles they find the way my crowd does), you’re missing out.  You might not know why they’re called click beetles either.  Rather than explaining it, take a look at this short video I took a few nights ago of a click beetle that made it’s way into my bathroom (where all click beetles seem to end up in my house).  The quality isn’t fantastic as it was taken in a poorly lit inner room at night with a hand held camera, but you’ll get the idea.  And make sure you have the sound on!  Clicking the arrow near the lower right corner and selecting 1080p after you click play will improve the image quality.

Isn’t that wild?!  And did you hear the clicks?  These beetles are called click beetles for a reason: they make clicking sounds when they do their super awesome ninja-like jumps.  Those jumps are possible due to this structure on the underside of the beetles:

clicking mechanism

Click beetle underside. The arrow points to the click mechanism. Pryophorus sp.

click mechanism side view

Click mechanism side view. Pyrophorus sp.

Every entomologist knows this much about click beetles:

1) They click
2) They jump
4) They’re flat, elongate beetles with spines on the middle section of the thorax (you can see them in the pictures)
3) Both clicking and jumping are made possible by the spine indicated by the arrow on the second thoracic segment (the middle section of the thorax) fitting into the groove on the third thoracic segment.

When I decided to write about click beetles, it occurred to me that I didn’t know exactly how this mechanism worked.  The online search was worthless as nearly every site simply copy and pasted the Wikipedia entry on click beetles, and that told me what I already knew – spine fits into groove, makes beetles jump.  Looking through my entomology books wasn’t much more helpful: spine fits into groove, makes beetles jump.  Before I dug into the literature on the subject, I decided to try one final textbook, The Insects: Structure and Function by the late, great Reg Chapman (a very lovely and brilliant British man who taught one of my first entomology classes in grad school).  The book is one of the most dense books I’ve ever read – and I read it cover to cover to prepare for my comprehensive exams for my Ph.D. – but it’s an amazing treasure trove of information about insects.  Reg’s book told me how the mechanism works.

First, the beetle arches the center of its body upward off the ground so that only part of the thorax and the tip of the abdomen are still in contact with the ground.  It then contracts the muscles around the spine.  Normally this would result in the movement of the thorax, but the spine catches on the groove so the thorax doesn’t move.  Instead, energy is stored up as the beetle continues to contract the muscle and the spine remains trapped in the groove.  Eventually, the spine slips off the groove and all of that energy is released.  The front and back ends of the beetle, the parts that were still in contact with the ground as it arched, snap upward off the ground at a high velocity.  The velocity is so great that the rest of the body is pulled up after them, launching the entire beetle into the air.  If this is hard to picture, imagine shooting a rubber band off your finger toward the ceiling.  You pull back on the rubber band with one hand while catching it on a finger of the other hand.  The rubber band represents the spine and the muscles attached to it while the finger is the groove.  Energy is built up as you stretch the rubber band further and further back, similarly to how the beetle stores up energy as it contacts the muscle around the trapped spine.  When you release the rubber band, the part you pulled back launches forward, releasing the energy stored in the rubber band and pulling the entire band off your finger in the process.  (Well, assuming you’re holding it right, otherwise it releases all that energy into your soon-to-be-painful finger instead.)  Now imagine the rubber band and finger setup inside the beetle and it should give you a pretty good picture of how this works.

So why do these beetles do this?  There are two main reasons.  This clicking-jumping behavior is likely primarily a strategy to avoid being eaten by predators.  Most things that try to eat a click beetle will think twice if the beetle launches up into their face as they try to eat it.  It’s a startle tactic: if they can distract the predator for even a moment or two they just might be able to run away.   You can see this in the video.  The beetle clicks when I (a possible predator) touch it, then it runs.  I think this anti-predator mechanism is likely very effective.  Watching one of my dogs messing with them certainly suggests that it is!  He’ll sniff the beetle, then jerk back in horror as the beetle launches itself into his nose.  He might then put a paw on it, at which point it will click again, so he’ll jerk his paw back.  He usually tries the paw thing twice before he leaves the beetle alone.  Granted, this only works so long as the other dog doesn’t see him playing with the beetle.  The smaller dog is so jealous the bigger one is getting something that she’s not that she’ll run over and eat the beetle, clicking or not, just so her brother can’t have it.  :)

But back to the beetles!  The other reason these beetles likely click is to be able to flip themselves over when they end up on their backs.  These beetles have rather wide bodies and stubby little legs, so they have a hard time getting themselves right side up again.  Clicking to the rescue!  The clicking mechanism works whether they’re right side up or upside down, so the beetle can simply click, launch itself in the air, and hope it lands on its feet.  If not, it will click again until it does.  You can see this in the video too.   The beetle easily rights itself every time I flip him over.  Pretty neat trick, don’t you think?

So now you know how and why these beetles jump.  I’ll end this post with a brief comment on variations in size and coloration in these beetles.  While most of the click beetles most people see are smallish, drab beetles, there are some amazingly beautiful click beetles in the world.  I leave you with pictures of what I think are the two most spectacular species found in Arizona.  Enjoy!

Chalcolepidius ostentus

Chalcolepidius ostentus. Not sure of a common name, but I call this one the really pretty click beetle. :)

Alaus zunianus

Alaus zunianus, the Zuni eyed elater

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Unless otherwise stated, all text, images, and video are copyright © 2010 DragonflyWoman.wordpress.com

The Sound of Summer

cicadaHere in southern Arizona, we have a lot of cicadas.  Evidence of their presence comes in two forms: 1) the husks remaining after they’ve crawled up onto a tree and burst out of their nymphal exoskeleton and become adults and 2) their loud sounds.  My sister and I used to collect the shells as kids.  Well, we did until my sister picked up one that still had the nymph inside.  It promptly grabbed ahold of her finger and terrified her.  I think she was maybe 4 or 5 at the time, but I doubt she’s picked up a cicada shell since, just in case there’s a surprise lurking inside.  I have no hangups of this sort, so I still collect them when I am lucky enough to see them.  I haven’t seen any for a few years now (honestly I haven’t been looking), but they always make me happy when I do.

cacadaThe sound is hard to ignore though.  I have a very sharp sense of hearing and the droning buzz of these insects is LOUD.  Sometimes it really starts to drive me nuts, but most of the time it provides a sort of loud white noise soundtrack to the summer.  I’ve actually come to associate this sound with summers in Arizona.

Maybe I’m noticing them more than I have in the past or perhaps there are cicadas closer to my house than usual, but they’ve seemed particularly loud recently.  A few mornings ago they were so loud they woke me up!  They were in the tree in front of my house, so the sound had to float through the open window, the living room, and a hallway to get to my bedroom.  Like I said – really loud!  So, I decided to record them.  The video below isn’t much in the way of a visual experience.  In fact, it’s a recording of a palo verde tree, one in which there was a cicada, so completely uninteresting.  I only present this in video form because I don’t have the upgrade necessary for me to insert sound files into my blog.  But listen to the sound on the video.  The noise was created by only two cicadas!  Two!!  They were making an incredible racket outside the front window while my husband and I were eating dinner, so I just had to capture it.

Without further ado, the sound of an Arizona summer.  For the most authentic experience, turn your speakers all the way up before hitting the play button!

I think it’s amazing that an insect a little over an inch long is able to make this sort of noise.  I can hear them over the evaporative cooler in my house, the traffic on the busy street nearby, and all of the comings and goings of my neighbors.  They’re impressively loud.  And thankfully they aren’t as active at night as they are during the day or I’d never get any sleep.

At some point in the future, I’ll cover how and why cicadas make these sounds.  Cicadas are pretty amazing animals (and gorgeous to boot!), so they’re definitely worthy of a more complete post.  For now, just sit back and enjoy the sound I hear all summer.  To get a better picture of the experience, envision sitting on a group of sharp little rocks under a stubby little tree with a handful of what are technically “leaves” (if you can call something a leaf when it’s a half inch long and an eighth of an inch wide).  Imagine the sun blazing around you at about 110 degrees (F) and the air sucks the moisture out of your skin.  Then layer on the ear-splitting sound of the cicadas screaming.  Ah, summer in Arizona.  Gotta love it!

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Unless otherwise stated, all text, images, and video are copyright © 2010 DragonflyWoman.wordpress.com

How to tell if your child is likely to become an entomologist

I’ve been hard at work writing papers based on my research recently, so I’ve been writing science galore!  Unfortunately, this means that I’m in scientific writing mode and I’m finding it hard to write a decent post for the blog.  I’ve started about 6 different posts, but none of them are turning out the way I want them to.  I’ll finish all of those other posts sometime, but I’m giving up for now and doing something non-scientific.  Today’s topic: how to tell if your child is likely to become an entomologist.  And I have embarrassing illustrations!  Behold this photo!:

kids with bugs

The Dragonfly Woman (right) and Little Sister Dragonfly as nymphs. Photo by Mother Dragonfly.

Shortly after I began grad school, this photo arrived in a package from my mom.  This pretty much sums up my childhood in Arizona, before my family moved to Colorado.  That’s me on the right in the smashing Little Red Riding Hood costume skirt/blue and white striped swimsuit/purple scarf ensemble and my sister is on the left rocking the tutu/single jellie look.  (For those of you that know me in person, yes my hair really was both straight and blonde as a kid!)  My sister and I wore these outfits often and generally looked pretty homeless.  Sadly, I still often look pretty homeless when I’m out doing field work.  While many field scientists I know buy $80 tech pants at REI, I am not about to spend that kind of money on something that will likely a) be ripped, b) become hopelessly stained, c) get acid burns, or d) all of the above within my first 3 excursions.  I buy my field clothes at Target and Goodwill thank you very much.  When I rip the whole butt out of my pants in some magnificently clumsy maneuver, I’m out maybe 10 bucks and don’t want to cry.  However, this also means I wear these horribly stained ratty clothes out in the field.  In other words, I haven’t changed my style much since I was kid.  My sister has thankfully upgraded her wardrobe and DOES buy those $80 tech pants (usually on sale), but she is a park ranger and not an entomologist.  I’m a bit harder on clothes than she is.  Park rangers also actually talk to people on a regular basis while we entomologists are prone to being somewhat reclusive.  I mean, who DOESN’T want to talk to someone who looks like a homeless person running through the park with a bug net over her head yelling, “AAAAAAAAAAHHHHHHHHH!” as she goes?  :)  You can tell from my wardrobe as a kid that I was meant to be a bug person.

I now draw your attention to that spot on the carpet I’m staring at in the photo.  And if you look really closely, maybe move your head around to change the angle, you can see that my sister is holding a string in her hands.  While the clothes are suggestive of future bug geekdom, the items at the end of the strings are an even better indication that I was doomed to study bugs for a living.  That spot on the carpet and the thing at the end of the string my sister is holding is this:

Cotinus mutabilis

Cotinus mutabilis, also known as the fig beetle.

This is an appallingly bad photo of an otherwise gorgeous beetle (I recommend you check out Alex Wild’s far superior photo of this beetle) called Cotinus mutabilis, or the fig beetle.  If you grew up in Arizona like I did, you might also call this a June bug even though it isn’t a bug.  (If you’re interested in what makes a bug a bug, please check out my post on the subject for details.)  Fig beetles are about an inch long and sport a velvety matte green on top and metallic green on the bottom – they’re amazingly beautiful beetles.  They’re also very gentle beetles that fly around southern Arizona during the summer.

So what, you might be asking yourself, are my sister and I doing with them in the photo?  We’re flying them of course!  My dad would catch the beetles for us, tie threads onto one of their hind legs, and give us the other end of the threads to hold onto.  When the beetles tried to fly away, they would get to the end of the tethers and start flying in circles around our heads.  We’d fly our beetles for about a half hour, then we’d untie the threads and let them go.  It’s one of my favorite childhood memories and we did this a lot.  In the photo, both of our beetles were wandering around on the carpet rather than flying.  You can tell that I am the one who ended up becoming an entomologist rather than a park ranger because I’m the one on the floor with my beetle.  Park ranger little sis is keeping a respectable distance between her beetle and herself.

I really love this photo.  My sister and I both look absolutely terrible (and my mom wrote this lovely sarcastic note on the back after it was developed: “Playing with June bugs on strings – in particularly attractive outfits – the way they usually look!”), but it’s a reminder of an activity I dearly loved as a kid.  And once you decide to take the plunge and turn that bug obsession into a career, your family starts to send you all of these photos full of clues that you were destined to become a bug geek from the start.  I have a feeling most entomologists have photos like this.  Display them proudly, fellow entomologists!  I know I do.

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Unless otherwise stated, all text, images, and video are copyright © 2010 DragonflyWoman.wordpress.com

The heartbreak of chiggers

chigger

A chigger. Image taken from http://animals.howstuffworks.com/ arachnids/chigger1.htm.

Ah, summertime.  In Tucson, this is a time of extreme discomfort if you’re outside due to the blazing sun.  In other less hot places in the world and for many people, summer means a fantastic time outdoors – family vacations, camping trips, rolling down grassy hills, hiking, etc.  Unfortunately, this is also the time of year when lots of people get up close and personal with chiggers, the subject of today’s post.

That cute little guy above is a chigger.  Yes, I do actually think these things are cute, but then I’m an entomologist with a passion for gigantic insects that stab things with their beaks to pump them full of digestive chemicals to eat them and scare the living daylights out of most people, including several entomologists I know.  (I’ve got video of giant water bugs eating if you want to see them in action:  Abedus and Lethocerus!)  Clearly I have questionable taste.  Don’t let those 6 legs fool you though – chiggers are NOT insects.  Instead, they are the larval form of a group of mites (which are actually a type of arachnid) called the harvest mites.  Similarly to how insects grow wings as they transition from their larval or nymphal stages into adults, chiggers gain a pair of legs during their transformation into nymphs.  They then go from an 8 legged nymph to an 8 legged adult.

So why are chiggers so bad?  If you don’t know, you obviously haven’t experienced these nasty little predators.  They feed on the tissues of a wide variety of animals, including humans, though we Homo sapiens are not their preferred host.  There are a lot of misconceptions about feeding chiggers.  Case in point: after my first day of class as a graduate student, a big group of students decided to go to lunch where we had the most magnificent argument over the feeding mode of chiggers.  Do they burrow under your skin when they feed?  Are they in there when you notice you’ve been bitten?  Or do they bite you and fall off?  If a big group of entomologists can’t reach a consensus about how chiggers feed, it’s no wonder that so many other people are confused!

Let’s set the record straight right now: chiggers do not burrow into the skin.  That’s what ticks do, not chiggers.  Considering how similar mites and ticks look, it’s understandable that people mix the two up.  But just how do chiggers feed?  And why are they a nuisance to the people unfortunate enough to bump into them?

Chiggers are commonly picked up in fields full of plants.  There, they wait for an animal to brush up against the plant they’re on and then run onto the animal.  Then they crawl around and find a safe place to start eating, somewhere they are unlikely to be brushed off before they finish their several hour long meal.  If you’re a furry mammal, this could be anywhere and the chiggers may simply climb down into your fur and start to feed – and many animals have no reaction to their presence at all.  We relatively hairless humans have many fewer places chiggers feel safe.  Instead, they go for places where you’ve got thin skin, dark crevices, or where clothes sit tightly against the skin.  This means that most people end up with their chiggers in places like their armpits, the backs of their knees, their socks, under the bands of their underwear (tops or bottoms), and sleeve cuffs.  Once they find a good place, they latch on tightly and start to feed.

chigger feeding

A chigger feeding. Image taken from http://animals.howstuffworks.com/ arachnids/chigger3.htm.

Unlike many blood feeding insects and their relatives the ticks, chiggers have very short mouthparts.  Those little dangly bits at the front end of the chigger in the picture above are the chelicerae, their mouthparts.  Now imagine the chigger in that photo shrunk down to a milimeter or a half milimeter in size, their actual size.  Like I said – very short mouthparts!  Chiggers don’t just eat the top layer of skin cells though – they go for the good stuff underneath.  To do this, they pierce the skin with their chelicerae, then inject saliva to digest the tissue and expand the wound.  The goop that is produced is slurped up by the chigger.  Remarkably, they also inject compounds into the wound that cause an immune response in the host animal, one that hardens the tissue around the bite site.  In essence, the hardened tube-shaped structure that forms (called a stylostome) is a straw that expands deeper and deeper into the host.  The chigger injects more saliva and sucks up more liquified tissue as the stylostome gets longer and longer.  That’s right!  Chiggers have tiny mouthparts, but they use their host’s own immune system to enlarge their mouthparts into a stylet like those of mosquitoes or a beak like those found in the true bugs!  Now if that isn’t amazing, I’m not sure what is.

So the chigger bites you, dissolves some of your tissue, and eats it.  Big deal, right?  Wrong!  These tiny little creatures are capable of producing some truly awful allergic reactions.  These aren’t the send you to the hospital, carry an epi-pen with you kind of response in most people.  Instead you itch.  You itch like you’ve never itched before.  Some people get massive itchy welts.  The itching is intense, so severe that people have been known to gouge welts out of their skin as they scratch and many people have reported that the pain of doing this and the ensuing scars are much easier to deal with than the itch of the bites.  Now the itching wouldn’t be so bad if it were just a few bites, but most people don’t get that lucky.  Instead they get tens or hundreds of bites from many individuals at one time (chiggers tend to be clustered together) that are located in inconvenient places (want to be observed scratching your armpit or your bra straps vigorously hundreds of times per day?) and don’t go away for 5-10 days.  That’s right – these little tiny animals can cause massive itching for 10 days or longer!  (Are you itchy yet?)

It’s much easier to avoid chiggers than deal with the itching they cause later.  If you know you’re going to be out where there might be chiggers, there are some precautions you can take to keep them off you.  First, wear long pants and long sleeves.  Tuck your pants into your socks for extra protection.  The less skin you have exposed the better.  Avoid walking through brush and stay on trails where possible.  Finally, get out of your potentially contaminated clothes and take a shower, scrubbing thoroughly, when you get home.  Chiggers can roam around for several hours before they settle on a place to eat, so showering can help wash them off before you are bitten.  If you are bitten, well…  I recommend a trip to the pharmacy to get the best hydrocortisone you can buy and hope for the best.

For a more thorough account of chiggers, I highly recommend reading Dark Banquet by Bill Schutt.  It’s a book about sanguivores, also known as blood-feeding animals.  It’s a fascinating books and had a great section on chiggers.  In fact, reading that section prompted me to write this post in the first place!  There is also more detailed information at the website where I found the illustrations, http://animals.howstuffworks.com/arachnids/chigger.htm, including some photos of welts formed due to chigger bites.

Enjoy your summer and avoid chiggers as well as you can!

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Building a Garden Pond for Aquatic Insects, Update

pondThe Biosphere 2 Science and Society Fellows lunch was held in May, so my time as a B2 fellow is officially over and a new cohort will begin in the fall.  The fellowship was a great experience in general, though I am particularly pleased with my blogging experience.  Thanks to everyone who’s been keeping up with my blog for the support and encouragement!  I’m going to keep blogging and hope to make this a permanent part of my scientific life.

I had a chance to check on the pond I built to attract aquatic insects at B2 during the tour of fellows’ projects we made before the lunch.  As promised, this post will be a report on the success of my pond a month after the installation.  It’s terribly overdue as I’m easily distracted by interesting things and kept putting it off, but it’s time to get to it!  If you missed the earlier posts and want to read about the planning and installation of the pond, there are links to all of the pond posts at the bottom of the page.

First, a photo of the condition of the pond the last time I saw it, in mid-May:

my pond

My pond, a month after installation.

Admittedly, there were a few problems with the pond.  The water ended up becoming murkier than I’d hoped.  It may eventually require the installation of a filter to clear the water up because it was hard to see to the bottom of the pond.  It could have been worse though and a month in the hot sun of southern Arizona is enough to cause some major algae problems that my pond didn’t appear to be having.  So, the pond water was pretty good, but could have been better.

The main problem the pond was having was the wind.  During the installation of the pond, the Biosphere 2 courtyard where it is located was quite lovely.  Three weeks later when I went to check on it and again at the fellows lunch, the wind was absolutely ripping through the courtyard.  That courtyard gets a lot of very strong winds apparently.  I’m not sure that the cattails I planted myself had been in the pond long enough to establish a strong root system and the majority of them had been ripped out and were lying across the top of the pond.  I can’t do anything to keep the wind down in the area, but I did replant the cattails that still looked healthy and supported their bases with a lot of rocks.  I’ll have to go back to check on it one more time to see if it worked or whether they fell over again.

The wind was also causing problems for my identification guides.  They were getting whipped around on their hangers and were spread across the courtyard both times I went to check up on the pond.  The ring was entirely missing from one of the guides as well.  I’m going to need to figure out a way to shelter the guides from the wind so that they’re not being strewn all over the area and they’re in a place visitors can actually find them.  Stupid wind!  It’s amazing how much wind that courtyard gets.

pond plants

Plants in the pond.

In spite of these rather minor hiccups, here were several things that made me very happy about the pond too.  First, most of the plants seemed to be doing pretty well.  The submerged plants were still looking good and the horsetails, irises, and reeds remained green and were standing upright in the pond.  This suggests that they rooted sufficiently to withstand the wind.  The floating plants weren’t quite as abundant as they were originally and some had clearly died, but there were several still living in the pond and those all looked bright and healthy.  Overall, the plant situation looked promising.  I’ll want to go back after the winter and see how many plants avoided freezing during the winter, but I think the plants will make it until the first freeze at least.

There were insects in the pond!  There weren’t as many species as I had hoped (the seclusion of the courtyard and/or the wind may have had something to do with it), but there were some beetles and some fly larvae in the pond.  Considering the goal was to attract insects to the pond, this was what I had hoped to see.  I expect the pond likely has more insects in it now as the warm weather prompts many aquatic insects to disperse to new habitats and the monsoons are coming up soon too.  Lots of insects move around once the monsoon rains begin.

Much to my great happiness, there was one insect type missing entirely from the pond: mosquitoes!  There had been many at my house by the time I checked on the pond, so I was very worried that there would be tons of them breeding in the water.  I looked really hard and I didn’t see a single one!  The flow of the water appears to be sufficient to control the mosquitoes, though I’ll definitely want to go check up on that again this summer just to be sure.  Mosquitoes are definitely something I want to avoid.

And finally, the water levels and the flow were both looking good.  The automatic filling system seemed to be doing its job well and the water was still flowing at a good clip.  Hopefully these will continue to work well long into the future.

Overall, I think the pond was looking pretty good the last time I visited it.  I want to go back sometime after the monsoon rains start to check on it again, but the conditions of the pond a month after installation were promising.  The goal of the project was ultimately to create a permanent educational display and so far the pond seems to be holding its own and going strong.  Yay!  My first successful pond!  Now I’m itching to build one in my yard…  :)

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Posts in this series:

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Unless otherwise stated, all text, images, and video are copyright © 2010 DragonflyWoman.wordpress.com