Meet the Beetles!

Meet the Beetles posterI wanted to let everyone know about an event that’s coming up this weekend at the Arizona-Sonora Desert Museum west of Tucson.  During the summer, the Museum is open late on Saturday nights so that people can visit when the temperatures are reasonable and see some of the interesting things that happen only at night in the desert.  This Saturday, August 28, there will be a special event: Meet the Beetles!  Dr. Wendy Moore, the new systematist in the University of Arizona’s Department of Entomology, will have live specimens of over 30 Arizona beetle specimens available, as well as a whole hoarde of professional entomologists (grad students, postdocs, and professors) to share what’s known about these beetles with the public.  It’s a fantastic opportunity to learn a lot about Arizona’s beetles from some very knowledgeable people – and we have some truly spectacular beetles!  The event runs from 7-9PM and will be located in the Desert Garden.  Admission for the Museum is only $7 after 4PM and only $2.50 for kids 6-12.  Kids 5 and under are free.  If you’re in the Tucson area on Saturday, this is a great event and one I highly recommend!

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Migratory Dragonfly Species – Common Species

In most of the dragonfly swarm reports I’ve been getting, I’ve had people tell me that they know nothing about dragonflies or how to identify them, though several of you have an expressed an interest in doing so.  So, I thought I would do something to help all of my ambitious reporters out!  Today, I’m posting images and descriptions of the most common of the American migratory dragonfly species, including males and females when they’re different, so that you can try to identify some of the dragonflies you’re seeing in those swarms.  The migratory species are all dragonflies, not damselflies (see my past post on the subject if you aren’t sure how to tell them apart!), and fall into two families: the darners (Aeshnidae) and the skimmers (Libellulidae).  You’re probably not going to get close enough to these to see some of the wing structures that make it very easy to tell these two families apart (I’ll be posting on this eventually), but the most common migratory species all look different enough that it should be pretty easy to distinguish them on the wing.

Let’s start with the darners.  The family Aeshnidae contains the biggest species of dragonflies in the world, so if you’re thinking, “Wow!  That’s a REALLY BIG dragonfly!” it likely belongs to this group.  The most commonly observed darner is this:

Anax junius adult

Common Green Darner (Anax junius) male

anax junius female

Common Green Darner (Anax junius) female.  Image taken from http://www.dragonflies.org/catalog.htm.

This is the common green darner or Anax junius.  This species is the most commonly reported migratory dragonfly in the U.S. and will be seen very often in swarms.  Things to look for: 3 inches long.  Bright green thorax in all individuals.  Bright blue markings on abdomen in mature males, green markings on brown bodies in females and immature males.  Some immature males might also have red abdomens.  “Eyespot” on top at front of head (clearly visible in image of male – click on the image if you wish to enlarge it).  Clear wings or with only minor duskiness, no distinct spots or markings.  Green darners are found throughout the United States and in southern Canada.

The other common migratory darner is this one:

epiaeschna heros

Swamp Darner (Epiaeschna heros).  Image taken fromhttp://www.dragonflies.org/catalog.htm.

This is the swamp darner or Epiaeschna heros.  If you live west of central Texas, you’re not seeing this one in your swarms!  Anywhere else, this is a darner commonly found in swarms.  Things to look for: Very large dragonfly, up to 3.5 inches long.  Dark brown body with narrow, bright green stripes on abdomen, thick green strips on sides of thorax.  Bright blue eyes.  Males and females similar, though female may lose some of the blue as she ages.  This dragonfly is found only east of Ohio in the north and east of Nebraska and Texas further south.

That’s it for the common migratory darners!  Most of the time, if you’re seeing what you think are very large dragonflies in a swarm, it will be one of the two species above.  Most of the Libellulidae (also known as skimmers) are smaller than the darners, though they’re still pretty big.  Most of the migratory skimmers are also very common species of dragonflies with wide ranges in the U.S..  These include this gorgeous skimmer:

libellula pulchella

Twelve Spot Skimmer (Libellula pulchella) male. Image taken fromhttp://www.dragonflies.org/catalog.htm.

libellula pulchella

Twelve Spot Skimmer (Libellula pulchella) female. Image taken fromhttp://www.dragonflies.org/catalog.htm.

This is the twelve spot skimmer or Libellula pulchella.  This is a very common skimmer found throughout most of the U.S. (except for the southwest) and southernmost Canada.  Count the number of black spots on the wings and you’ll know where it got its common name. Things to look for: Medium-large dragonfly, 2 inches.  Body dark brown, males often with white prunescence on thorax and abdomen.  Females similar, but lack most of the prunescence.  Three dark spots on each wings, including one at the base, middle, and tip.  White spots may be present between the black spots.  The eight spot dragonfly is similar, but the dark spots do not reach the edges of the tips of the wings.

This species is very closely related to the 12 spot:

Painted Skimmer (Libellula semifasciata). Photo copyright Darrin O’Brien and taken from http://bugguide.net/node/view/218767/bgimage.

This species is the painted skimmer or Libellula semifasciata.  It’s range is similar to the swamp darner above and is restricted to the eastern half of the U.S. Things to look for: Medium-large dragonfly, just under 2 inches.  Pattern on wings is distinct: amber coloration at base and tip, brown spot at center and near tip.  Abdomen with a subtle orange-yellow tint in males, tending more toward brown in females.  Sexes very similar otherwise.

Now we have some gliders, my favorite dragonflies!

Wandering glider (Pantala flavescens)

Wandering Glider (Pantala flavescens)

This is my favorite dragonfly, the wandering glider or Pantala flavescens.  Considering my long-standing interest in dragonfly responses to weather patterns, there’s a good reason for this dragonfly to be my favorite.  But that’s a story for another time.  For now, you’ll want to look for these characteristics: Medium-large dragonfly, just shy of 2 inches.  Wings long relative to body, broad.  Body yellow brown, but can appear golden in flight.  Abdomen tapered, thicker at base than at tip.  Males and females similar.  This species is common across the U.S. and southeastern Canada.

The wandering glider’s close cousin is this species:

Spot-winged glider male (Pantala hymenaea)

Spot-Winged Glider (Pantala hymenaea) male

The spot-winged glider, or Pantala hymenaea, is very similar in shape to the wandering glider, but bears some distinctive differences.  Things to look for: Medium-large dragonfly, just shy of 2 inches.  Abdomen grey and black, appearing mottled, and tapering to a point.  Wings long and broad, mostly clear with a distinctive dark round spot at the base of the hindwings (look for the spot in the center of the hindwings right next to the body in the image above).  The location and shape of the spot spot is only seen in this species.  Males and females similar.  Found throughout most of the U.S. and southeastern Canada.

And finally, we come to the saddlebags.  The first saddlebags is this:

tramea carolina

Carolina saddlebag (Tramea carolina)

This gorgeous dragonfly is the Carolina saddlebags or Tramea carolina.  This group of dragonflies is rather closely related to the gliders, which should be obvious if you compare the shape of the wings. Things to look for: Medium-large dragonfly, 2 inches.  Long, broad wings.  Hindwings with wide deep red-brown spot at the base.  Body bright red, with two black abdominal segments the near tip of the abdomen.  Males and females similar.  Common across most of the eastern U.S.  Note: this species may be replaced by the red saddlebags (Tramea lacerata), which looks nearly identical, in swarms if you are in the western part of the country.  The red saddlebags hasn’t ever been officially declared a migratory species, however.  You can distinguish the two by looking at the color of the face (Carolina has a violet forehead while red does not) and the black abdominal segments (the black doesn’t wrap all the way around the sides of the segment in the reds as it does in the Carolinas), but these characteristics may be difficult to distinguish in the field.  Luckily, the ranges of these species don’t overlap very much except in eastern Texas and Oklahoma.

And finally, we have the other very common saddlebags:

Tramea lacerata

Black Saddlebags (Tramea lacerata)

This is the lovely black saddlebags or Tramea lacerata.  I think this one is gorgeous!  Sleek black dragonfly, very common in Tucson.  Love it!  Things to look for: Medium-large dragonfly, just over 2 inches.  Long, broad wings with broad brown-black spot filling the 1/4 of the hindwing closest to the body.  Abdomen black, often with white spots on the upper surface near the base and the tip of the abdomen.  White spots darken over time.  (You can see the white spots in the image above – just click on the image to enlarge it, and look halfway between the end of the wings and the tip of the abdomen.)    Males and females similar.  Common throughout much of the U.S. except in North Dakota, Montana, and Wyoming.

That does it for the dragonfly species you’ll commonly find in migratory swarms!  I suspect that many of the same species are present in static swarms as well (please see my post Dragonfly Swarms Revisited for more information about the two types of swarms), so hopefully this post will be handy for those of you who wish to ID the dragonflies you’re seeing in swarms.  Next time I’ll cover the less common species of migratory dragonflies and comment on some of the other species that have been popping up in swarms around the country.  Until next time!

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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 © 2010 DragonflyWoman.wordpress.com

Damselflies and Antlions – What’s the Difference?

I get a lot of questions about insects when people learn that I’m an entomologist.  These frequently sound something like, “I saw this little brown beetle in my house the other day – what is it?”  Most of the time, I have a hard time identifying an insect based on a description like this.  You often need to see an insect to properly identify it.  At the very least you need a photo.  There are, after all, close to a million known species of insects and there may be over 10,000,000 insect species in all!  One person can’t possibly know all of the species of insects, no matter how great their memory is.  However, there are some things that I can identify based entirely on a quick and dirty description.  One of the easiest is the difference between a damselfly and an antlion.  They look very similar so I completely understand why people have a hard time telling them apart, but there are some obvious distinctions if you know what to look for.

First, let’s take a look at a damselfly:

damselfly adult

Damselfly adult

This is a member of the family Coenagrionidae, so it is one of the very common little blue damselflies you’ll see around ponds.  What do you notice about the structure of this insect?  Look closely at the wings.  Click on the image to enlarge it if you need to.  How many wing veins and cells in the wings do you see?  The wing veins are the lines on the wings while the cells are the little open square parts between the wing veins.  The color on damselflies is often distinctive.  They fade badly once they are dead, but this damselfly used to be a brilliant blue.  Now look at the head.  Do you see any antennae?  Probably not.  They’re visible (there’s one sticking off the right side of the head right above the right eye, looks like a little hair or a piece of dust), but they’re small, bristly things that most people wouldn’t even notice.  They’re definitely shorter than the length of the head.

Now look at the antlion:

Antlion

Antlion

Can you see why people get these two insects mixed up?  Even some beginning entomologists have a hard time telling the two of these apart!  Look closely at this insect like you did with the damselfly.  First, you should note the color.  This insect is brown, as are almost all antlions.  While some damseflies are brown (especially females), there are many that are brightly colored.  If you have a brightly colored individual with this shape, it’s a damselfly, not an antlion.  Next, look at the wings and observe how many cells there are.  How many do you see?  Antlions belong to the order Neuroptera, the net-winged insects.  Antlions, like other neuropterans, have tiny cells in their wings and a whole lot of them, many more than you’d ever see in a damselfly.  If you see an insect with this shape with tons of little cells instead of 100 or so large, open cells, you’re looking at an antlion.  But the easiest way to tell them apart is by looking at the head.  What do the antennae look like on this insect?  They’re very long, much longer than then length of the head, and thick.  In other words, they’re quite conspicuous, very unlike the tiny, bristly antennae you can barely see in the damselflies.  If you see an insect with this shape that has long, luxurious antennae, it’s antlion.  If it has antennae that are barely visible, it’s a damselfly.  Easy, right?

Of course, there’s one other obvious distinction.  Damseflies are diurnal, which means that they are active during the day.  Antlions are nocturnal, so they are active at night.  You might occasionally find an antlion out during the day, but it’s very unlikely to see a damselfly at night.  Most of the time it’s easy to tell these two insects apart based solely on when you see them!  But, it’s always good to check the length of the antennae and the number of wing veins to be sure.

Now that you know the difference between an antlion and a damselfly, you might start noticing how often these two insects are mixed up.  There is a tank top that I would dearly love to have that depicts an antlion.  The people selling it have it labeled as a dragonfly (not even a damselfly!).  Rubber stamps, especially ones based on old engravings from the 1800’s or early 1900’s, often erroneously depict antlions when they’re supposed to be damselflies.  And all sorts of people feel the need to put antennae on dragonfly and damselfly images.  I don’t know why this is so common, but you will see dragonflies and damselflies with long curly antennae everywhere you look.  This is actually my single biggest pet peeve as an entomologist.  I couldn’t care less about using the word bug when you should use insect, but stick antennae on my favorite insects and you and I are going to have words!

Next time I’ll likely post about how to tell damselfly nymphs apart from stone fly and mayfly nymphs.  They’re easy too, so I hope you’ll check in again soon!

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Text copyright © 2010 DragonflyWoman.wordpress.com

Color Polymorphisms in Dragonflies

In my last post, I talked about the dragonflies that my fiancee and I saw on our recent photographic trip to Sweetwater Wetland in Tucson.  We took a lot of photos of dragonflies and as I went through them, it occurred to me that there is an important topic related to identifying dragonflies that I have not covered so far in my blog: odonate polymorphisms.

If you’re like most people (including me until I’d been an entomology grad student for almost a year), you’re now thinking to yourself, “what is a polymorphism?”  You probably already know more about polymorphisms than you might think!  First, let’s take apart the word to define it.  The root “poly” means many.  Think back to geometry and polygons – a polygon is a shape with many sides.  The root “morph” means shape or form.  So, the word polymorphism effectively means “many forms.”  Form can refer to shapes, colors, sizes, and other characteristics of biological organisms that might vary between stages, sexes, or individuals within the same species.

You probably know about a few species that exhibit polymorphisms already.  Birds are a classic example of sexual dimorphism (di = two, so dimorphic species exhibit two forms): males take one form while females take another.  In birds, the males are often one color while the females are another.  In most cases, the males attract the females, so the males are the more colorful, showy individuals.  In general, the more brightly colored males are healthier and better able to produce strong offspring with a high chance of survival, so females will choose mates that are brightly colored over less colorful males.

Peacock and peahen

Peacock and peahen

As an example, consider peacocks.  Peacock males are VERY showy with their long, elegant tails while the female peahens are much less colorful and have much shorter tails.  Peacocks with the biggest, baddest tails get all the girls while the less showy males have to settle for leftovers (sometimes younger or less healthy females) or simply cheat their way into getting a mate.

Other animals that show dimorphisms are deer and elk.  Again, the males are trying to attract the females and are willing to fight other males for them.  Elk or deer with big racks are generally better able to successfully fight other males.  As in birds, the buck with the biggest rack is likely healthier than the bucks with smaller racks – they have to be getting enough food and other resources to grow those antlers in the first place.  The doe chooses her mate from the available males and usually selects the one that is best able to win fights, the one with the best antlers.  Because the females are not fighting amongst themselves and are not trying to attract the males, a doe doesn’t need antlers.  So, some elk and deer have horns (the males) and others do not (the females).  They are also sexually dimorphic.

Now let’s get back to the dragonflies.  Like in birds, elk, and deer, it is the role of the male dragonflies to attract female dragonflies if they wish to produce offspring.  Thus, male dragonflies are often much more brightly colored than the females and many species are sexually dimorphic.  Take, for example, the blue dashers, or Pachydiplax longipennis.  If you follow my blog, you’ve seen this one before, but here he is again in all of his elegant glory:

Blue dasher (Pachydiplax longipennis) male

Blue dasher (Pachydiplax longipennis) male

Blue dashers are very common mid-sized dragonflies across a big section of the United States, including Arizona.  The males are easy to identify based on their bright green eyes and the bluish coloration of their bodies.  The abdomen is covered in a waxy substance, or prunescence, which can give them a bit of the whitish look you see in the male pictured here.  Blue dashers are perchers, so you’ll commonly find the males sitting on emergent vegetation or on bushes and/or other plants alongside lakes and ponds.  They sit and guard their territories from their perches, waiting for females to come into their areas so they can mate.  In contrast, the females are known to spend a much greater part of their time away from water and only come to the water to mate and lay eggs.  I found this female sitting on a tree branch far from the water:

Blue dasher (Pachydiplax longipennis) female

Blue dasher (Pachydiplax longipennis) female

Can you see how different the female looks compared to the male?  The males are a whitish bluish color while the females are largely black!  The female blue dashers are about the same size and of similar shape compared to the males, but they have very different body colors, making this a dimorphic species.  Female blue dashers are also very easy to identify.  Just look for a black abdomen with yellowish or brownish stripes on each section of the abdomen.  The abdomen tends to be a bit stumpy compared to the male abdomen, so the wings look disproportionately large.  In fact, this is the origin of the species name longipennis, which means “long winged.”

Blue dashers are considered dimorphic because there are two main forms, but they are not exactly sexually dimorphic either.  Odonates are not sexually mature when they molt from nymph to adult and require a period of a few days to complete their maturation.  Immature individuals, including the males, look like the females.  So, the mature males are blueish and the immature males, immature females, and mature females all tend to look like the picture of the female.

Many dragonflies and damselflies follow similar patterns.  Green darners (Anax junius) are actually polymorphic:

Anax junius mating pair

Green darner (Anax junius) pair

As you can see in the photo, the male (the dragonfly in front) is green and blue while the female is green and green-brown.  Immatures of both sexes can have a reddish abdomen and the females can have brown sections on their abdomen.  Sometimes the females even have about the same blue on their abdomens as the males!  Because the green darners have so many different color patterns, they are considered polymorphic.

Not all dragonflies exhibit dimorphism or polymorphism.  Some dragonflies are monomorphic (mono = one) such that all indviduals look about the same, regardless of sex or age.

Next time I’ll post some more photos from the Sweetwater trip and go over how to identify them.  I hope you’ll stay tuned!

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Text and images copyright © 2009 DragonflyWoman.wordpress.com

Meet the giant water bugs!

This time I’m actually going to write about giant water bugs, as promised!  As I write this, I am sitting in a lab at Arizona State University measuring the oxygen consumption of water bug eggs.  I’ll write more about that in another post, but first allow me to introduce you to the giant water bugs!

This gorgeous creature is Lethocerus medius:

Lethocerus medius

Lethocerus medius

Isn’t he a formidible looking insect?  It’s hard to tell from the picture, but this male is about 2.5 inches long from the top of the head to the tip of the abdomen, and that doesn’t include the long, pointy bits sticking out of the back!  The size of these bugs is where they get the “giant” part of their common name.  They get “water” because they are aquatic insects and live in water.  The “bug” portion of the common name comes from the fact that they are true bugs, i.e. they belong to the insect order Hemiptera .  The common name giant water bug thus tells you a lot about these insects – the giant water bugs are really big aquatic insects!

The giant water bugs belong to the family Belostomatidae.  What makes an insect a belostomatid?  First, let’s review why this insect is a true bug.  We can tell he is a bug because there are hemielytra present and, if you flip him on his back and look under his head, his mouthparts are piercing-sucking mouthparts.  These are the characteristics of true bugs.  You can read more about what makes an insect a bug in my post about the true bugs.

You can tell this is a belostomatid, as opposed to any other true bug, because it has the following:

1. Raptorial forelegs.  Predatory insects, such as the giant water bugs, mantids, and assassin bugs, frequently have enlarged forelegs to help them grab and hold their food.  If you eat live animals, it’s important that you are able to subdue them!  Raptorial forelegs help you do that – they’re full of huge, strong muscles.  For a comparison in humans, think of a skinny, nonathletic 10 year old and a professional weight lifter (or Fezzik in The Princess Bride!).  Who is going to be able to lift more and/or hold onto something more tightly?  The weight lifter, of course, because he has bigger, stronger, and better developed muscles than the 10 year old.  The same thing goes with insects.  Big forelegs help you grab and subdue prey so you can eat your food.  (Interesting aside: there is another type of enlarged foreleg, called a fossorial foreleg, that helps insects that live underground!  They need strong muscles in their forelegs to help themdig and move through dirt.  If you’ve ever seen a mole cricket, you know what these look like.)

2. Swimming hairs on the legs.  See all that brushy stuff coming off the legs?  Those are called swimming hairs.  Insects have a hard time moving through water and have all kinds of adaptations that help improve their mobility.  Having thick hairs on your legs helps you swim better than if your legs are smooth.  Think about the way we relatively hairless humans swim.  Which is easier: swimming with flippers or swimming without them?  It’s easier to swim with flippers because the increase your surface area.  By attaching flippers, you are effectively making your feet bigger and flatter.  More of your “body” is coming into contact with the water with each kick, so you move further and with less effort than you would without the flippers.  Swimming hairs work the same way.  They are nature’s swimming flippers!

3.  Retractable respiratory appendages.  Take a second look at those long pointy bits sticking off the back of the Lethocerus in the picture above.  Those are respiratory appendages, called respiratory siphons or air straps depending on which type of water bug you’re looking at.  What makes the water bugs different from other insects with respiratory appendages (such as the water scorpions – I’ll be posting about these sometime as well as they include my very favorite insect!) is they are able to retract theirs, pulling them mostly or entirely within their bodies!  So why do giant water bugs have these structures?  Well, giant water bugs require air to survive, the same air that you and I breathe.  I’ll write more about giant water bug respiration in a future post (this is something I study in my lab), but for now just know that these structures help the giant water bugs collect air.  Not all giant water bugs have the long siphons though.  The giant water bug in the image below is Abedus herberti.  Take a look at the respiratory appendage indicated by the arrow:

air straps

Abedus herberti. Arrow points to the air straps.

Most of the giant water bugs actually have these little short air straps rather than the long respiratory siphons of Lethocerus, but both types of appendages work the same way.  Regardless of the type of appendage, all water bugs are able to pull them into their bodies.

So now we know that belostomatids are true bugs and that they have raptorial forelegs, swimming hairs on their legs, and retractable respiratory appendages.  All giant water bugs share these characteristics, regardless of their subfamily, genus, or species.  Next time I’ll delve a little bit deeper into the different types of water bugs found in the U.S. and then talk a bit about what I’m doing with my resrearch during my visit to ASU.  Stay tuned!

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Text and images copyright © 2009 DragonflyWoman.wordpress.com

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

Dragonflies and Damselflies – What’s the difference? (Adults)

A couple of posts ago, I went over the difference between dragonflies and damselflies in the nymph stage.  Today I’m going to cover the difference between dragonfly and damselfly adults.  They’re very easy to tell apart once you know what you’re looking for, so let’s drive right in!

This is a dragonfly:

Anax junius adult

Adult dragonfly (Anax junius, male)

A few thing to notice about the dragonfly:

1) The eyes are broadly rounded and lie mostly flat against the head
2) The thorax (the green part the wings are attached to in the picture above) ismore broad than the abdomen (the blue part in this dragonfly)
3) The forewings and hindwings are different shapes
4) Body is quite large (The dragonfly in the picture, a green darner, is about 3 inches long!), though there is a lot of variation in size

All dragonflies share these characteristics.  Also, if you saw this dragonfly sitting on a plant or on the ground, it’s wings would be held in the same position you see in the picture, spread out flat and to the sides of its body.

Now compare the dragonfly picture to this picture of a damselfly:

damselfly adult

Damselfly adult (unidentified sp.)

Look for these things in the damselfly:

1) The eyes are largely spherical and protrude off the sides of the head
2) The thorax (the segment where the wings are attached) is narrow, about the same width as the abdomen
3) The forewings and hindwings are very similar in size and shape
4) Usually fairly small (at least compared to the dragonflies)

If you saw a damselfly resting at a pond, it’s wing would look different from a dragonfly’s.  Rather than holding it’s wings flat and to the sides of it’s body, it holds its wings straight up, pressed together over the top of its thorax.  This is what you would see in the field if you saw one from the side:

damselfly adult

Damselfly adult, side view (Enallagma boreale)

Ultimately, if you’re at a pond or river, the easiest way to tell whether an odonate you’re looking at is a dragonfly or damselfly is to look at how it holds it’s wings while resting.  If they’re lying flat, parallel to the ground, you are looking at a dragonfly.  If the wings are pressed together, held over the bug’s back, you’ve got a damselfly.  So what happens if the odonate you’re looking at doesn’t ever stop flying?  Let’s think back to the difference between perchers and fliers from my last post.  Fliers are almost always dragonflies and damselflies are almost always perchers.  If it doesn’t stop to rest every few minutes, it’s probably a dragonfly.

Okay.  Now imagine you have two pinned odonate specimens, one dragonfly and one damselfly, rather than seeing them in the field.  The wings are spread apart on both.  Can you tell the two insects apart?  We know you should look at the shape and location of the eyes, the width of the thorax, whether the forewings look like the hind wings, and the size of the body.  See if you can tell which one is which in this picture:

dragon and damsel

A dragonfly and a damselfly - can you tell them apart?

The answers are listed below so you can’t cheat!  Scroll down to check your answers.  Hopefully you got them right!

If you have problems remembering the difference when you don’t have a list of their characteristics sitting right in front of you, here’s a good way to remember them.  Think of the names of these insects, dragonflies and damselflies.  What sorts of images do these names conjure in your mind?  I personally think of medieval stories about dragons holding damsels in distress hostage to use as bait for daring knights.  Think of dragonflies as you would the dragon in this image: robust, strong, powerful, and really big.  The damselfly is more like the damsel in the dragon and the damsel image.  They are smaller, softer, and weaker than the dragon.

One final note about dragonflies and damselflies as I finish this up.  The odonates have become very popular with non-scientists recently and dragonfly watching has become a sort of sport similar to bird watching.  With the publication of several excellent field guides which contain all of the species in a region or the country, it is easy for people who are not familiar with insects to identify the dragonflies and damselflies they see without specialized training or equipment.  All you need is a good field guide and a pair of binoculars!  If this is something that interests you, I have two field guides that I haul around with me when I’m out camping, bug collecting, on class field trips, etc, that I would like to recommend.  The first is Dragonflies Through Binoculars by Sidney Dunkle.  The book is about $30 retail (less on Amazon.com) and covers all of the dragonflies in the U.S.  The book contains excellent distribution maps and flight season information, color photos of every species, the common and scientific names for every species, and multiple pictures for species where the males and females (and sometimes the younger males) are different colors.  The descriptions for each species highlights the distinctive characteristics you should look for to tell them apart from other similar species.  It’s a really excellent book.  The downside: no damselflies!  I recently acquired a book that covers dragonflies AND damselflies in the western U.S., Dragonflies and Damselflies of the West by Dennis Paulson, so that I have a field guide for the damselflies too.  It has many of the same features as Dunkle’s book and costs about the same, but includes both dragonflies and damselflies.  The downside to this book: the book doesn’t cover the whole country, so you need another book if you’re going somewhere east of Kansas or Nebraska.  Still, it gets the job done in my area and I find it very useful.  Dragonfly watching is a fun activity and I hope you will give it a try!  There’s nothing quite like the feeling of checking another dragonfly, one you’ve never seen before, off your checklist.

Answer to the dragonfly vs. damselfly quiz above: A is the damselfly (one of the largest in the country!) and B is the dragonfly.

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Text and images copyright © 2009 DragonflyWoman.wordpress.com