Dragonflies from the swarm

I’ve already posted twice about the dragonfly swarm my friend and I came across last week on the lake where we work, Lakeside Lake in Tucson.  While we watched the swarm, we also collected some of the dragonflies to add to our insect collections.  Because dragonflies tend to lose their colors VERY quickly in collections, it has become common practice for dragonfly enthusiasts of all levels of expertise to scan their specimens on standard flatbed scanners to preserve the colors as they are in life.  If you would like more information how to make your own dragonfly scans or would like to see some amazing images made using this process, I recommend taking a look at the website Digital Dragonflies.  (This is a great website to consult if you want to try to identify a dragonfly you’ve seen and you don’t have a field guide.)  Or check out the book written by the Digital Dragonfly creators, A Dazzle of Dragonflies. This book is absolutely gorgeous and I recommend it to anyone with even a passing interest in dragonflies, even if you only look at the pictures.

We found 4 species of dragonfly in the swarm, all of which are common in the Tucson area.  We’ve seen all of these at Lakeside many times, just not in the numbers we saw in the swarm.  I only managed to catch three of the four species (and if you know anything about catching dragonflies, especially these particular species, you know that’s pretty good!), so I’ll only go through the ones I have images for.  First, let’s meet the wandering glider, Pantala flavescens:

Wandering glider male (Pantala flavescens)

Wandering glider male (Pantala flavescens)

This handsome dragonfly is my favorite of all the dragonflies.  (If I ever get a tattoo, this is what I’m getting!)  This is a fairly common dragonfly in the Tucson area, though I find they’re much more abundant during the monsoons than at other times of the year.  This might have to do with a behavior they exhibit – they sometimes travel very long distances in front of storms!  I’ll post more about Pantala flavescens in a future post, but for now just know they’re amazing insects.  For a relatively boring looking dragonfly, it’s certainly got some fantastic behaviors.

How can I tell this is a wandering glider?  There are several ways.  This is a fairly big dragonfly with a wingspan of about 2 inches.  When they fly, they tend to appear brightly yellow-orange. There aren’t  many dragonflies with this sort of coloration, so it’s distinctive.  They are also fliers and rarely perch.  When they do perch, they tend to rest vertically (perpendicular to the ground) instead of horizontally (parallel to the ground) like other species.  If you manage to be lucky enough to catch a male, like the one above, and look at it head on, his face will be bright orange.  His eyes, as you can see in the image above, will be reddish.  His abdomen will be yellow to orange with black spots that widen the further down the abdomen you look.  And finally, the cerci (those little pointy bits sticking off the back end) are black.  This dragonfly gets its common name of glider from the shape of its wings.  See how the hindwings are much more broad than the forewings?  This is a flight adaptation that helps make them one of the strongest fliers of all the dragonflies.  There aren’t all that many dragonflies with wing structures like this, so if you see it, you can narrow down your options quickly.

This dragonfly, the spot-winged glider (Pantala hymenaea), is closely related to the wandering glider:

Spot-winged glider male (Pantala hymenaea)

Spot-winged glider male (Pantala hymenaea)

Compare the wings of this dragonfly to the image of Pantala flavescens above and you’ll see they’re about the same shape.  That makes this a glider as well.  These are very easy to tell apart from their other Pantala relatives, even though they do rest vertically, are also fliers, are about the same size, and have very similar shapes.  In flight, these dragonflies will look reddish or brown instead of yellow.  The eyes are grey with a reddish spot on the top, so they’re not red all over as they are in P. flavescens.    Their faces are red instead of yellow.  The easiest way to tell this dragonfly from the previous one, however, is the dark brown, round spot at the base of the hindwings.  It’s visible in the image above and if you look closely, you will be able to see it when these dragonflies are in flight.  In fact, you can see it in one of the photos I posted in my last post.  If you see a dragonfly with very broad hind wings with a dark, rounded spot at their base, you’ve got a spot-winged glider.  However, sometimes in flight they can be difficult to tell apart from the saddlebag dragonflies, the group to which the last species I’ll discuss here belongs, at least to the untrained eye.  This dragonfly is Tramea onusta:

Red saddlebags male (Tramea onusta)

Red saddlebags male (Tramea onusta)

It’s also called the red saddlebags.  All of the saddlebags (we have 6 species of Tramea in the United States) have broad hindwings like the gliders and are likely close relatives.  However, they have dark, broad bands on their wings that run along the base of the wings from the top to the bottom.  These bands can be narrow or wide and the width will help determine which type of saddlebag you have.  For example, here in Arizona, we have four species of saddlbags.  I can tell this is a red saddlebags because the body coloration is distinctly reddish and the band on the wings is wide.  The Antillean saddlebags and striped saddlebags, though reddish, both have narrow bands.  And it’s very easy to tell this dragonfly apart from the black saddlebags, a dragonfly you commonly find in the same locations as the red saddlebags in Tucson, because the red saddlebags are red and the black saddlebags are black.  (Bet you didn’t see that coming!)  The saddlebags are pretty easy to tell apart from most other dragonflies based solely on the dark band on their hindwings.  If you see a dark stripe running along the base of the hindwings, it’s a good bet you’re looking at one of the saddlebags.

The last species we saw was the black saddlebags, Tramea lacerata.  They’re the only black saddlebag species, so they’re very easy to tell apart from the others!

Since I wrote about the swarm last week, I’ve received several comments and e mails about swarms that other people have seen.  The four species we saw in this swarm are known to do this swarming behavior and it’s common for them to swarm in mixed groups like the one we observed.  I’ve been hearing reports of many other dragonfly species forming swarms though.  If you see a swarm, it might include these speices (and hopefully you can identify them now if it does!), but it could include other speices as well.  Regardless, if you happen to see one of these swarms, consider yourself lucky!  It’s an amazing thing to see so many dragonflies flying around together at one time.

I’ve been on a big dragonfly kick recently, but next time I’ll be shifting gears to my own research.  I’m making a trip up to Phoenix next week to do some research in a lab at Arizona State University, so it’s time to introduce you to my research study subjects, the amazing giant water bugs!

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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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Text and images copyright © 2009-2010 DragonflyWoman.wordpress.com

Photos from the swarm

I went out to Lakeside Lake with a friend early this morning to take some photos of the dragonfly swarm that’s been forming there.  (See my previous post for more information about the swarm and a video of the behavior.)  The swarm’s been forming every morning this week!  The dragonflies were flying constantly and darting here and there very unpredictably, so it was nearly impossible to get a good shot, but I got a few I thought were worthy of showing here.  My apologies for the general blurriness – these things are FAST!

Pantala hymenaea

Spot wing glider (Pantala hymenaea)

Pantala hymenaea banking

Spot-winged Glider (Pantala hymenaea) banking during a turn

Pantala flavescens

Wandering glider (Pantala flavescens)

A few things I noticed about the dragonflies in the photos I took:

1) The forewings of the dragonflies move separately from the hindwings.  I already knew this, but it’s hard to see it when they’re flying around because their wings move so fast.  It’s very obvious in the photos though!

2) When the dragonflies turned sharply in flight, they usually kept their heads parallel to the ground.  Even though their bodies were twisting and turning as they glided about, their heads remained in about the same position the whole time. This resulted in some pretty gnarly looking photos where the dragonflies’ heads looked like they were on upside down!  I unfortunately didn’t not get a clear shot of this to show you…

3) Dragonflies can definitely fly backwards.  Dragonflies are among the most agile of flighted animals and part of what makes them so agile is their ability to fly backwards, a very difficult maneuver.  It was frustrating to get a shot all lined up only to have the dragonfly zoom BACKWARDS out of the photo at the last second!

4) Dragonflies at rest are a LOT easier to photograph than flying ones!  Case in point: the photo I posted last week (see myDragonfly Sighting post) was of a dragonfly sitting on a bush branch.  I took 3 photos of the dragonfly before it took off and I considered all 3 good enough to post.  Today I took 377 photos.  About a third of them didn’t end up having any dragonflies in them at all.  Of the 236 that actually contained dragonflies, the vast majority showed the dragonflies as blurry, indistinct blobs of color.  I only got 13 shots I thought were decent at all, and my best one, the wandering glider above, is still far from perfect.  I like the photo more for the contrasting colors than anything else.

Regardless of the difficulty of the photography, it was still really fun!  If nothing else, it was amusing to TRY to get some good photos of these guys.  (I can’t help it – I’m drawn to the difficult photographic subjects, if only so I can practice and improve my skills.)  Even if we hadn’t gotten any good shots, it still would have been worth the trip to the lake just to see so many dragonflies in one place at one time.  This swarm is pretty darned impressive and watching hundreds of dragonflies lazily flying around a hill in the morning sun is a fabulous way to spend a weekend morning.

Be sure to check out the photo my friend posted from this morning’s shooting.  The photo she posted is better than any of mine, so I hope you’ll take a look!

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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.

    I welcome any information that you’re willing to provide about your swarm!  The more details you’re willing to provide, the more helpful your report will be, but I’ll happily take anything you’re willing to share.  Reports so far have varied from a few words to novellas, and it’s all useful.

    Thanks!

    (Added June 30, 2010)

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    Text and images copyright © 2009-2010 DragonflyWoman.wordpress.com

     

    Dragonfly swarm!

    I work out on a lake once a week as part of my job.  We’re managing the water quality of the lake, which involves a lot of hot, hard work and heavy lifting in the sun on a metal boat.  Sometimes the job is really awful, especially during the summer when it’s over 100 degrees in the shade and super humid thanks to the evaporation from the lake.  A few days ago, my coworker/friend and I got out to the lake as early as we could to avoid the forecasted 108 degrees.  I’m glad we got there early because we were treated to the most spectacular dragonfly display I’ve seen so far!  Take a look at the video of this behavior I posted on YouTube so you can see what it looked like:

    Isn’t it fun to see so many dragonflies flying together at one time?  The swarm was made up hundreds of male dragonflies, all flying over the grass on the hill adjacent to the lake.  There were also several different species making up the swarm.  My friend (also a biologist) and I weren’t sure what the dragonflies were up to, so we speculated about what they might be doing.

    One possibility was that the dragonflies were patrolling the area over the grass, protecting a territory they had set up.  Dragonflies, especially the males that made up the swarm, tend to be highly territorial.  You would usually see only one male in an area at a time, unless a male from another area is challenging the resident male.  It would thus be very unusual for so many male dragonflies to be in a single area at the same time, especially a position away from the water.  Dragonflies are known to be tricked into thinking they have found water when they have not on occasion (see my post about dragonflies patrolling over cars), but there was no reason to suspect they were being tricked en masse.  If dragonflies commonly mistook grass for water, they wouldn’t have been around for as many millions of years as they have!  The grass hadn’t been recently watered either, so they likely didn’t mistake it for water because it was wet.

    When dragonflies patrol their territories, they tend to exhibit distinct flight patterns, making the same motions over and over again until something (food, mates, competitors) enters their territory and they veer off path to investigate.  The dragonflies in the swarm exhibited erratic, jerking flights, not the controlled, fluid flights of typical patrolling males.  Dragonflies of different species also tend to fly at different heights while patrolling and/or exhibit different flight patterns.  All the bugs in the swarm were  flying at the same height and using the same motions.  With all of these facts in mind, we ruled out patrolling over the grass.  The members of the swarm clearly weren’t patrolling.

    We ruled out the possibility that the males were looking for mates for many of the same reasons.  A female dragonfly usually needs water to be able to lay her eggs.  She will fly out over the water, find a place that looks safe for her offspring, and mate with the male that controls that area.  If the dragonflies weren’t mistaking the grass for water, they wouldn’t be looking for mates.  Females wouldn’t come to the area over the grass to mate because the area wasn’t suitable for egg deposition.  So, mating probably wasn’t the reason for the swarm.

    We eventually decided this had to be a feeding behavior.  If you looked just right, you could see thousands of little insects flying above the grass.  These little insects were buzzing around all over the place.  If the dragonflies were chasing little bugs that were flying erratically, they would be flying erratically themselves.  Also, there really wouldn’t be any reason why they should be over the grass instead of the water unless there was some benefit to their being there.  Because they find mates at the water, each moment a male dragonfly spends away from the water represents a lost chance for mating.  However, if there were a ton of food available on the hill that wasn’t available over the water, there was a benefit to flying over the grass.  If the food was particularly abundant, i.e. there was enough to go around, it would also explain why the dragonflies were tolerating one another and not chasing their competitors away.  It had to be a feeding swarm.

    We collected a few dragonflies from the swarm (MUCH easier to catch in the swarm than as individuals over the water!), watched the swarm for a while, and then got to work.  It was a hot, miserable day on the lake, but my friend and I agreed it had been worth taking the time to watch the dragonflies.  It ended up making up for the discomfort of the work.

    I looked into the swarming behavior when I got home from work and learned that it is indeed common for some dragonfly species to fly in large feeding swarms like the one we saw.  Looking into it further, I learned that the four species I was able to identify within the swarm are the ones most commonly known to make these sorts of feeding aggregates.  I hadn’t ever read about dragonfly swarms or seen one before, but it was gratifying to know that my friend and I were able to figure it out on our own, simply by thinking about what we knew about dragonflies and their behaviors.  It just goes to show that the more you know about an insect’s behavior, the better you are able to explain new behaviors you haven’t seen before!  Regardless, I was ecstatic to see the swarm!  It was an amazing experience and one I will remember forever.

    In my next post, I’ll go over the species we found and how to identify them so you’ll know some of the species to look out for if you ever come across a dragonfly swarm yourself.  The dragonflies that made up this swarm are easy to tell apart.  In another post, I’ll talk about what we think the dragonflies were eating and the evidence we found for it.  Stay tuned!

    _______________

    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!

    _______________

    Want more information?

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

    _______________

    Text and video copyright © 2009-2010 DragonflyWoman.wordpress.com