Thursday, March 8, 2012

A Blue Dasher dragonfly obelisking in the sun...

When it's hot out, you'll often see dragonflies perched on a stem in the sun with their long bodies (abdomens) sticking straight up towards the sky. It looks like they are doing some sort of insect handstand, but they are really working on thermoregulation, and their strange posture is called obelisking. Not all dragonflies obelisk to cool their bodies, some drop their abdomens downward, some shade themselves with their wings, some circulate hemolymph through their abdominal sections, and some dive into the water...

A male Blue Dasher (Pachydiplax longipennis) dragonfly obelisking in the hot sun to regulate his body temperature.

By raising their abdomens straight up, dragonflies reduce the surface area heated by the sun, which helps them cool their bodies. Blue Dashers are famous for obelisking. They often take the stance even when the temperatures are not that high, and males also seem to use the posture as a threat display when defending their territory. Additionally, if the sun is low in the sky and it's cooler, they use the obelisk posture to heat themselves by exposing more of their abdomen to the sun's warming rays.

A male Blue Dasher dragonfly has several distinguishing field marks--a powder-blue abdomen tipped in black, amazing turquoise-green eyes in a white face, brownish areas on the wings, and very noticeable stripes on its thorax.

Blue Dashers are common in numbers but not in looks! With powdery blue abdomens and bright turquoise-green eyes, it's hard to pass them by without a second look!

Blue Dashers are "perching" predators. They like to perch in one place and fly out to catch their prey, returning to the same perch to eat it. Because they spend so much time sitting and waiting in one place without moving, thermoregulation by adjusting their posture works well for them (source: Obelisk posture, Wikipedia). Blue Dashers are formidable predators and will eat all sorts of insects including mosquitoes, flies, butterflies, moths, mayflies, flying ants and termites (source: Idaho State Univeristy).

Even as a naiad (the nymph form that lives in the water), Blue Dashers are "sit and wait" predators, hiding behind rocks and logs until the prey goes past.

...an interesting fact: Blue Dasher naiads can tolerate low levels of oxygen in the water, so just as lichens are an indicator species of a healthy environment, a lot of Blue Dasher naiads in relation to other species in an area can indicate low water quality (source: Idaho State University).

(I photographed this guy on 6/13/2010 on Pinckney Island in Hilton Head, SC. It was really hot that day and beautiful. The field guide I use to help me identify dragonflies is "Dragonflies and Damselflies of Northeast Ohio," by Larry Rosche, Judy Semroc, and Linda Gilbert)

24 comments:

dAwN said...

Fabulous shots and thanks for all that information. I did not know about obelsking.

Matt Latham said...

Brilliant set of a great looking dragonfly

Laure Ferlita said...

Wow! What gorgeous coloring! Great post!

TexWisGirl said...

these are fantastic macros! and i appreciate the education on obelisking, too!

Jerry said...

Wow what stonking photos. I especially love the close-ups. Also your blog is so informative and interesting. Keep it coming!

forgetmenot said...

AMAZING macro photos of that colorful and beautiful dragonfly. You take stunning photos. Thank you for sharing your pics as well as the information. Have a wonderful weekend. Mickie :)

Guy said...

Hi Kelly

I am not sure how you trained a draogonfly to pose but the results are amazing. Seriously I have never seen nicer photos of one and the term obelisking has made my day maybe my week.

All the best.
Guy

Roy said...

Brilliant macros Kelly.

The GIPSY in the PARLOUR said...

Wow! I'm so impressed, these are some of the most beautiful insect photos I've ever seen. So loved reading all about Blue Dasher, hope to meet one someday ...

Montanagirl said...

These photos are just superb! So clear, and what a colorful guy! Your narration is very informative. I did not know any of that.

KaHolly said...

I applaud your photos and your post today. Great read!

Elva Paulson said...

Wow! and Double Wow! May I ask what lens you are using and approximately how far you were from the dasher? We get a lot of good dragonfly photos, but these take my breath away.

Gillian Olson said...

Thank you for this beautiful and informative post. I had no idea why they did this. These photographs are amazing. Again thank you for sharing, glad I dropped by.

Kelly said...

I've had lots of questions about the camera and lens I used to photograph this dragon. Here it is:

...I took these photos with my older Nikon D700 Camera and my older Nikon AF-S VR-Nikkor 70-200mm 2.8G lens (pushed to 200mm).
I also had my Nikon 2x teleconverter attached (taking it to 400mm). They are hand-held shots. I was about 15-20 feet away...no closer. I then cropped the images down in Aperture.

The Nikon lenses really take the vibration out, plus this may sound weird, but I use a yoga breath when I take my photos. I soften my facial muscles as I exhale, and when I reach the stillness at the end of the breath I shoot. (I know that sounds all crunchy, but it really works! I'm a yoga teacher, and you can take a lot of vibration out of your body with your breath.)

Elaine said...

Exquisite shots!!

Bob Bushell said...

Absolutley brilliant of the dragonfly, truly beautiful photos.

Banjo52 said...

I cannot believe the detail in these shots. And once again some great info as well. Never was very interested in these guys till now. Thanks.

Ana Mínguez Corella said...

Hi Kelly!!!...
Beautiful photos and interesting blog... You are an artist... Greetings from Spain (Madrid)...

Z said...

Wow! Gorgeous!

Cheryl said...

Besides being blown away by the photos themselves, the information was such a gift. I've wondered why I often see so many dashers hanging around near a couple small bodies of water while I see none at others. The obelisking has always fascinated me: I just wasn't sure why they were doing it.

Javier Conejero said...

Magnifico trabajo fotográfico y aún mejores pinturas. un blog para seguir.
enhorabuena!
saludos

Janice K said...

Looks like a handstand to me. Such lovely colors--great pictures,of course!

Kelly said...

...thanks, everyone for you kind words! I remember what a gorgeous day it was when I photographed this guy. It was sooo hot and the sweat was dripping on my face. It was so cool to watch this guy in the obelisk posture. His gorgeous turquoise-green eyes kept me looking!!

Tammie Lee said...

an interesting post kelly
you make me look forward to having them around this summer

your photos are fab!