Where to look for dragonfly identification information

A lot of the people who have sent me dragonfly swarm reports have expressed an interest in identifying the dragonflies they’re seeing in their yards.  I think this warrants a post on where to find information about dragonfly identification!  Today I’ll cover some of the books I really love and some of the best online resources you can use.  I’ll also tell you what you can do if you’re stuck and need the advice of an expert to help you figure out the dragonflies that you’ve seen.  I’m a scientist, so I have a lot of technical books that I can use to help me identify dragonfly species very precisely using a microscope and other special tools, but this post is meant to help people who are not dragonfly experts to find accessible information.  I hope you will find this useful!

Dragonflies Through Binoculars cover

I am a huge book lover, so I personally turn to books whenever I want to ID a dragonfly or damselfly that I’ve seen.  I have several favorites, but I use two over and over again because they are so thorough and include ALL of the species in a particular area.  Dragonflies Through Binoculars by Sidney Dunkle is a great source of information about the North American dragonflies.  It includes photos, descriptions, distribution maps, and flight dates for each of the species.  It also does a great job of highlighting the distinguishing characteristics so you can tell species apart even if they are very similar in appearance.  This is a great book and I always take it with me when I travel.  The only downsides are that the book doesn’t include the damselflies and it it now 10 years old, so some of the information might be slightly out of date.  The book I turn to again and again when I want to have all of the dragonflies and damselflies in one place is Dragonflies and Damselflies of the West by Dennis Paulson.  This book shares all of the great features of Dunkle’s book, but it is is newer and includes the damselflies.  I LOVE the behavioral information in this book!  However, if you live outside of the western part of the US and Canada, this book isn’t going to be as useful.   Luckily, dragonflies are popular, so there are a lot of great resources out there!  Your best bet is getting on Amazon and searching for either dragonfly or odonata and your state or country.  There are tons of local guides available, so it’s definitely worth looking for one for your area!

odonata central screen capture

There are several great online resources, but I am particularly fond of Odonata Central.  Odonata Central is an amazing website!  It include up-to-date information about flight seasons, distributions, characteristics, etc.  Even if you know nothing about the dragonflies you’re seeing, Odonata Central is an excellent resource.  For example, to see a list of every species in your area, you can click on the checklist link at the top of the page.  The website will guide you to your location (in the US, you can get information for your county) and a list of all of the species in your area will appear.  You’ll also see links for photos, maps, and information about each species on the list.  By clicking through the images and reading the descriptions, you will likely be able to identify the species in your area.  The best part: this works for almost any location, including areas outside of North America.

Many, many people (including Odonata Central) have photo galleries of dragonflies online and simply scrolling through photos can take you a long way toward identifying the species you see in your area.  I love the Digital Dragonfly website’s image gallery, though not all American species are included.  Because I live in southern Arizona, I also frequently check websites such as Arizona Odonates and California Dragonflies and Damselflies for photos and identification information.   To find websites with information about your local dragonflies and damselflies, check out the links page at Ode News or the links page at Odonata Central.  They both have comprehensive lists of good, reliable information available online.

Bug Guide screen capture

If, after you have tried the field guides and scrolled through photo galleries, you just can’t decide whether your dragonfly is a neon skimmer or a flame skimmer, where can you turn?  There are two great resources available at your disposal.  The first is BugGuide.  In addition to great photo galleries, you can also submit photos of dragonflies or damselflies and request an ID.  Bug Guide is a network of insect and spider enthusiasts who volunteer their time helping people ID bugs they’ve seen.  When you submit an ID request, one of the many Bug Guide users will likely know which species you’ve seen an give you an ID!  To get the most specific response, take a photo of at least the back and the side of the dragonfly or damselfly as clearly as you can because the characteristics that distinguish species are most often in these areas.  Then upload your photos to the Bug Guide by clicking ID Request at the top of the page and following the instructions.  Most people get responses to their inquiries within a few days.

Did you know that there are entomologists all over the US trained to help non-entomologists identify insects?  Land grant universities are often required to maintain research collections of various groups of organisms (including insects, snakes, fish, crustaceans, plants, etc) and to provide outreach to the public.  If you have a land grant university in your area, you likely have someone who can help you ID insects and provide information about them at the university.   The Cooperative Extension service is the main outreach component of most land grant universities and nearly every county in the US has an office.  The Cooperative Extension service employs a large number of entomologists, so give your county office a call!  If your county’s entomologist can’t ID a dragonfly for you, he or she likely knows a person who can.  And finally, Odonata Central maintains a member directory that includes many dragonfly experts and/or enthusiasts around the world.  If you click on View All at the top of the page and search for your location, you might be able to find a odonatologist nearby who can answer your dragonfly ID questions and give you more information about your local species.  That said, tracking down their contact info might not be easy in every case.

As I said earlier, dragonflies are very popular insects, so there are tons of resources available!  In fact, the volume of information available can be overwhelming if you don’t know where to begin.  Hopefully, this post will direct you to the best resources available and make it as easy as possible to figure out which dragonfly species you’ve been seeing.  Good luck!

I’m getting away from dragonflies for the next few posts, but check back near the end of October for a summary of the results of my dragonfly swarm data collection effort this summer.  I’ve collected more reports than I ever thought I would, so it should be an interesting read!

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

Dragonfly Swarms: Static Feeding Swarms

At long last, I am finally getting to the information about static swarms in dragonflies!  Apparently posting once a week is a bit ambitious for my current schedule and even my weekend became one giant black hole of work.  I’ve had no time to blog!  Better cram this post in quick while I have a few free minutes…  :)

Before I jump into what’s known to science about static dragonfly swarms, take a moment to ponder the amazing swarm depicted in this image I found online:

Isn’t that glorious?!  I can’t be sure that this is a real photo, but based on what others have reported and what I’ve observed myself, this is certainly not outside the realm of possibilities!  The people in the photo aren’t enjoying the experience, even though the dragonflies in the swarm were completely harmless.  I wish I were in their place!  I would run out and stand in the middle of the swarm, soaking up the sound of the dragonfly wings fluttering against one another and the sight of several thousands of my favorite animals flying in a single location.  This is what my heaven looks like!  (And yes, you read that right: I did just say that my heaven involved massive numbers of flying insects.  What can I say?  I’m an entomologist!)

Now for the science!  If you’ve read any of my swarming series, you know that dragonflies migrate, sometimes in mass migratory swarms, and that migrating dragonflies have patterns of behavior similar to migrating birds.  I have also speculated, based on my own observations and those of people who reported swarms to me early this summer, that the non-migratory swarms (what I call static swarms) are feeding swarms.  Today, I’m going to go over what’s known about these swarms.  Unfortunately, most of this information is either buried in the scientific literature where it’s largely inaccessible to the public or in a $100 dragonfly book that, while truly brilliant, is also largely inaccessible.  And let’s face it.  Apart from college libraries, only odonatologists (scientists who study dragonflies) and other entomologists are going to shell out that kind of cash for a dragonfly book.  For those of you who don’t LOVE DRAGONFLIES SO MUCH that you’re willing to run out and fork over 100 bucks for a book (i.e. you’re normal), I’ll summarize what is known about static swarms here!

First of all, the static swarms are almost always feeding swarms!  I’ll go over the reasons why you might see these feeding swarms in a particular area in a moment, but first a few interesting facts.  First, this behavior appears to be exclusively anisopteran.  This means that the behavior is observed in dragonflies only, not their close relatives the damselflies.  This is probably because dragonflies exhibit vastly superior flight compared to damselflies. However, among dragonflies, many species of both perchers and fliers will take part in the swarms and fly for extended periods of time.  Both males and females swarm, though males are more commonly observed.  Swarms can be made up of several different species, and can even include other organisms, such as the vertebrate birds and bats.  If birds or bats are present, they will usually be found just above the dragonflies, feeding on the same insects the dragonflies are eating rather than on the dragonflies themselves.  And for those of you who are shocked at the number of dragonflies in the swarms you’ve see, you likely only saw the tip of the iceberg!  In one of the only studies looking at the number of individuals swarming within a population, only 16% of the dragonflies in the area participated in the swarm.   Just think: if you see 1000 dragonflies in a static swarm, that means that there were likely 6250 total dragonflies nearby!

You’ll most often see dragonfly swarms near dusk or dawn, and it’s thought that the dragonflies can see flying prey (most often mosquitoes or non-biting midges, but also termites, ants, and honey bees)  better when the sun is close to the horizon.  During these times, you may notices that dragonflies appear very suddenly, fly in circular patterns over a very specific area for some time, and then disappear as quickly as they arrived.  This is because the dragonflies are attracted to large groups of prey organisms.  Once the prey numbers drop or they become less active (e.g. as it get darker), the dragonflies move on.  If the prey return the next day, the dragonflies likely will too.  In some particularly productive areas where prey are consistently available, you might even see a swarm form nearly every day for months.

There are several reasons why dragonflies might congregate in one area versus a similar area nearby, but in nearly every case there is an abundance of prey species present in the area containing the swarm.  Dragonfly swarms will form where other insects are swarming.  Most people have seen a big swarm of gnats at one point.  Those swarms are like a dragonfly buffet!  The dragonflies will swoop in and out of the fly swarm, picking off flies and eating them on the wing before going back for more.  This is likely what happened in August when the dragonflies descended on Milwaukee.  Massive numbers of mosquitoes in the area drew dragonflies into the city and large swarms formed where the mosquitoes were congregating.  Dragonfly swarms often form when there is a seasonal emergence of ants or termites as well.  This was the case in the swarm I witnessed.  The ants and termites were emerging out of the grass and the dragonflies were catching and eating them as they emerged.

Dragonflies might also be attracted to objects that attract other insects.  If prey insects are consistently attracted to a particular object, dragonflies can learn to associate that object with a good meal.  In one study, dragonflies were found over a set of traps intended to attract other insects, feasting on the insects flying in toward the trap.  The prey insects eventually stopped coming to the traps, but the dragonflies returned for several more days.  In this case, the dragonflies were attracted to the traps and not the insects themselves because they’d learned to associated the traps with an abundance of prey.

Dragonflies might also be observed swarming in areas where a weather front has just passed through.  Insects often get trapped in fronts and are pushed along with the winds for some time before being deposited somewhere else.  When they finally free themselves from the front, they might find the dragonflies ready!  Dragonflies take advantage of these windfalls of prey by forming swarms and eating the insects as they arrive.  This sort of feeding also happens during migratory flights.  The same fronts that deposit large numbers of prey insects in an area help the dragonflies fly long distances, so prey is readily available when the dragonflies stop to rest and feed.

In wooded areas, many insects will congregate in sunny, open patches.  Lots of dragonfly swarms form in small sunny patches to take advantage of the other insects that are attracted to the spaces.  The swarms of prey insects will move as the sun changes position, os the dragonflies will move too.

In high winds, insects will congregate in lee areas (areas protected from the wind).  Lees promote dragonfly swarming behavior because of the high abundance of insects found in these areas.

Finally, and I think most remarkably, some dragonflies will swarm in areas where insects are being stirred up due to some sort of disturbance.  Mowing your lawn?  It disturbs the small insects living in your grass and cause them to fly around more than they usually would.  The prey draws the dragonflies in and swarms form.  Similarly, some dragonflies have learned to follow large, slow moving objects (these could be people, bicycles, cows, cars, etc) because they disturb prey insects as they move and encourage the prey to fly – often into the eager grip of a hungry dragonfly.

So all of this boils down to one simple concept: any time you have an abundance of dragonflies in an area as well as a significant prey population, you are likely to see dragonfly swarms.  The behavior is thus fairly common in many different species of dragonflies.  That said, the chances of a single person seeing more than one or two swarms in their lifetime in a single area can be quite low.  The conditions have to be just right for swarms to occur, perfect for both a large number of prey insects AND a large number of dragonflies to exist in the same area at the same time.

Next time (and I’ll get the post up much more quickly this time), I’m going to discuss some of the references available for identifying dragonflies, both in print and online.  In the meantime, keep sending me swarm reports!  I am beyond thrilled with the participation in my swarm project, so keep ‘em coming!

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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

Amazing insect egg story in National Geographic this month

A lot of my readers know that my research focuses on the giant water bugs. What I haven’t blogged about very much yet is this: my dissertation work is centered around giant water bug eggs.  I am an insect egg fanatic!  So, you can imagine my delight when this image popped up in my Facebook feed yesterday:

insect egg

Image by Martin Oeggerli, published in the September issue of National Geographic.

Insect eggs are featured in National Geographic this month!  (It figures that, for the first time in years, I not getting National Geographic when this article appears…)  The photos are images created using a scanning electron microscope, one of the tools I use in my own research.  They have been painstakingly recolored from their original black and white format to reflect the colors of the eggs in nature.  The results are absolutely stunning.  I highly recommend that you read the article and take a look at the photos (though if you’re hoping that the structures of the eggshell will be identified, you’re going to be a bit disappointed – leave a comment below if you want to know the name of a structure in any of the photos).  There is also a video describing how the photos were colored.  The coloration is superb and took an incredible amount of work to produce.

I am mildly disappointed that there are so few non-butterfly or moth insects represented in the images because many other insects have extraordinary eggs, but the photos are so gorgeous I can’t help but love them anyway.  My favorite is the red lacewing butterfly image because it is what the most beautiful plant I can imagine would look like.    If any of you check out the photos, I’d be thrilled to know which one is your favorite and why.  Leave a comment below!

I’ll be posting about my own work using the scanning electron microscope to look at egg structures in the next few months.  If you like the National Geographic article, I encourage you to check back and read about eggs that very few people have ever seen up close.

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

Migratory Dragonfly Species – Less Common Species

Well, my plan to get the less common migratory dragonfly species up last week failed miserably.  I was going to try to get it done before I went on my little Labor Day mini-vacation.  After working 16 hour days for two weeks before I left, I realized that wasn’t going to happen.  ”No problem!” I thought.  ”I’ll bring my materials with me so I can do the post while I’m on vacation!”  Then I forgot to bring most of the things I needed to do the post.  Basically, the plan was doomed from the start!  So, I’m finally back home and once again have everything I need to get the post done.  Sorry for the delay!

The dragonflies depicted and described here are migratory species, but they’re less commonly observed migrating than the ones included in the common migratory species list.  You’ll see these species in swarms, either static or migratory, but you’d want to look here after you look at the pictures of the common species.  They’ll make up a smaller part of the swarm or will not swarm with the same regularity that the common species exhibit.  Still, I thought this would be a useful resource for people who wish to identify the dragonflies they see swarming in or over their yards.

Like last time, let’s start with the big dragonflies, the darners in the dragonfly family Aeshnidae.  This gorgeous animal is the lance-tipped darner (Aeshna constricta):

Aeshna constricta male

Aeshna constricta male.  Image by David E. Reed and from http://bugguide.net/node/view/69841.

Aeshna constricta female

Aeshna constricta female, green form. Photo by Larry de March and from http://bugguide.net/node/view/138814.

I think the mosaic darners from the genus Aeshna are some of the most beautiful dragonflies and this one is no exception!   Things to look for: Large, 2.8 inches long.  Males with brown thorax with blue stripes on the side.  No stripes on face of male.  Front-most stripe on side of thorax green on half closest to legs, blue on half closest to wings in males.  Bright blue markings on abdomen in mature males.  Females have all markings either blue, bright green, or yellow depending on form.  Females may have orange-brown wing tinting on the half closest to the body, especially in yellow form.  Lance-tipped darners are found in the northern half of the United States and in southern Canada.  You can tell them apart from other migratory mosaic darners in their range based on the lack of stripes on the face and the wedge shaped cerci (those dangly bits hanging off the back).

The other less common migratory darner is this one:

Aeshna eremita male

Aeshna eremita male. Photo from http://www.holoweb.com/cannon/lakedf.htm.

Aeshna eremita male side view

Aeshna eremita male side view. Photo from http://www.holoweb.com/cannon/lakedf.htm.

This is the lake darner, or Aeshna eremita. This species looks very similar to the other mosaic darners (including the lance-tipped darner above), but it’s the biggest one in the US and Canada.  Things to look for: Large, 3.1  inches long.  Both sexes with brown thorax.  Stripes on side of thorax blue above and green below with a conspicuous notch in the center (this is very easy to see in the image of the side of the dragonfly at left).  Found in northern United States and southern Canada, with a narrow finger extending southward to Utah and Colorado in the west.  You can tell them apart from other migratory mosaic darners in their range based on the size and the big notch in the stripes on the side of the thorax.

Distinguishing the mosaic darners without catching them can be difficult, even for people who know them well!  If in doubt, try to get a good photo of the top and side of the dragonfly (like the one above) or get as good a look at the color patterns on the abdomen and the thorax as you can.  I’ll tell you where you can send photos or look for good identification information to ID your dragonflies in future post (coming soon!).

The skimmers (family Libellulidae) are much easier to tell apart, especially the migratory species!  This one is very easy:

Celithemis elisa male

Celithemis elisa male. Photo from http://www.dragonflies.org/cel_mt.htm.

Celithemis elisa female

Celithemis elisa female. Photo by Steve Scott and from http://bugguide.net/node/view/60577.

This is the calico pennant (Celithemis elisa), one member of a genus of highly recognizable, medium sized dragonflies.  Things to look for: 1.8 inches long.  All individuals begin their adult lives with the yellow markings in the image of the female, but markings become red as males age.  Pattern and coloration of the wings are specific to this single species – if you see this pattern of wing spots, it’s this species.  You’ll find this species across the eastern half of the United States and a very small section of extreme southeast Canada.

Next up we have a dragonfly with a very limited distribution:

Erythemis berenice male

Erythemis berenice male. Photo from http://www.dragonflies.org/eber_1mta.htm.

Erythemis berenice female

Erythemis berenice female. Photo from http://www.dragonflies.org/eber_3fsa.htm

Meet the seaside dragonlet (Erythrodiplax berenice)!  I’ve had a chance to see this beautiful dragonfly on a trip to visit my sister the Park Ranger and it’s a stunner, especially the females.  Things to look for: Small dragonfly, only 1.3 inches.  Slender bodies.  Males start out with some yellow markings on the top of the abdomen, but these fade to black with age.  No coloration on the male wings.  Females similar shape with yellow markings on top of abdomen.  One female form with the black thorax seen in the males, the other (as seen at left, the spotted form) with a series of black and yellow stripes along the thorax.  Spotted female with brown spots on wings.  Found along the eastern and Gulf coasts and along southwestern lakes with high salt contents.

Now for the king skimmers from the genus Libellula.  The first one is the bar-winged skimmer (Libellula axilena):

Things to look for: medium-sized dragonfly, 2.2 inches long.  Brown thorax and abdomen.  Abdomen with a thick black stripe down the center top.  Males may appear white in some areas as they mature due to prunescence.  Black markings across the upper surface of all four wings.  This pattern is sometimes seen in the slaty skimmer (Libellula incesta), which is found in the same areas and is about the same size.  Distinguish the males by looking at the face: slaty skimmers have a brown face while the bar-winged skimmer has a black face.  Also, the slaty skimmer is not known to be migratory.  Found through the deep south and in the states along the Atlantic coast.

The next king skimmer is this one:

Libellula quadrimaculata

Libellula quadrimaculata. Photo from http://bugguide.net/node/view/194329.

This is the four-spotted skimmer or Libellula quadrimaculata.  Things to look for: medium dragonfly, 1.7 inches long.  Wings with black spots along top margin of wings, halfway between base and tip.  Hindwing with a black triangular spot at the base of the wing.  Abdomen brown near thorax and darkening to black near the posterior end, yellow stripes along side.  Both sexes similar.  Common in the northern half of the US, the Four Corners states, and most of Canada.

And the last king skimmer:

Libellula vibrans male

Libellula vibrans male. Photo from http://www.dragonflies.org/lv_10mtb.htm.

Libellula vibrans female

Libellula vibrans female. Photo from http://www.dragonflies.org/lvib_2ft.htm.

This is the great blue skimmer or Libellula vibrans.  Note the similarity of the female to the bar-winged skimmer, with which it shares part of its range.  Things to look for: medium-large dragonfly, 2.2 inches long.  Dark black spot along upper margins of wings, halfway between base and tip, and a black streak at the base of each wing.  Tips of wings amber.    Male body pale blue-white with blue eyes.  Females brown with a black stripe down the center of the abdomen, blue eyes.  Distinguish from bar-winged skimmers based on wing coloration patterns and the color of the eyes.  Range throughout southeastern US.

And we’ll finish up with three of the small dragonflies:

Pachydiplax longipennis

Pachydiplax longipennis male

Blue dasher (Pachydiplax longipennis) female

Pachydiplax longipennis female

This is the blue dasher, also known as Pachydiplax longipennis.  Things to look for: Small to medium body, 1-1.7 inches long.  Males pale blue-white, sometimes with black and yellow striped thorax, and bright green eyes.  Females black with yellow markings on body.  May have some coloration on the wings, light brown or amber in color.  Found throughout most of the US except the northernmost states of the west-central section.  The blue dasher is a very common species in much of its range and is often seen at small ponds, such as those found in yards and small parks.

And last but not least, two meadowhawks!  This one is very common:

Sympetrum corruptum male

Sympetrum corruptum male

The variegated meadowhawk or Sympetrum corruptum. This is likely the dragonfly you’re seeing if you see a migratory swarm west of the Mississippi River.  Things to look for: Smallish sized dragonfly, 1.5 inches long.  Body mostly grey with a red stripe down the center of the abdomen.  Red markings wrap around the abdomen as well, demarcating the boundaries of the abdomen’s subsegments.  Abdomen also has a series of small, white spots along the lower edge of the side.  These spots are more prominent in the females than the males.  Females replace the red markings with yellow on the abdomen.  Both sexes may look tan as they fly.  Found throughout the western half of the US and southwestern Canada.

And finally, the ruby meadowhawk (Sympetrum rubicundulum):

Sympetrum rubicundulum male

Sympetrum rubicundulum male. Photo by Stephen Cresswell and from http://www.insectsofwestvirginia.net/d/sympetrum-rubicundulum.html.

This species unfortunately looks nearly identical to another meadowhawk (the cherry meadowhawk, Sympetrum internum) and shares its range with it, but this species is a known migratory species and the cherry is not.  Things to look for: Small dragonfly, 1.3 inches long.  Abdomen red with black markings on sides.  Wings veins dark (they’re orange in the cherry meadowhawk).  Face yellow or brown (red in cherry meadowhawk).  Abdomen rather bulbous where it meets the thorax, narrows through the center, and expands again toward the back.  Found throughout the northeastern quarter of the US and parts of southern Canada.

And that’s it for the migratory dragonfly species!  Between the common and the less common species, y0u’ll likely find the majority of the dragonflies you might see in swarms in your area.  Next time, I’ll go over what’s known about static dragonfly swarms (feeding swarms) and then I’ll make some suggestions for where to go for dragonfly identification information.  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!

_______________

Want more information?

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

_______________

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