Archive for the ‘natural science’ Category

Blue-faced Meadowhawk (Batch 3)

October 21, 2017

This gallery features photos from Batch 3 (of 4) showing male Blue-faced Meadowhawk dragonflies (Sympetrum ambiguum) spotted during a recent photowalk around a vernal pool at a remote location in Huntley Meadows Park, Fairfax County, Virginia USA.

The next photo is for you, Michael Powell.

The last photograph is my favorite in this batch.

Related Resources

Copyright © 2017 Walter Sanford. All rights reserved.

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More Blue-faced Meadowhawk

October 17, 2017

Batch 2 (of 4). Please look at the full-size version of each photo.

Several male Blue-faced Meadowhawk dragonflies (Sympetrum ambiguum) were spotted near a vernal pool at a remote location in Huntley Meadows Park, Fairfax County, Virginia USA.

The last photograph is my favorite in this batch. Which photo is your favorite?

Related Resource: Blue-faced Meadowhawk dragonflies [Batch 1].

Copyright © 2017 Walter Sanford. All rights reserved.

Great Spreadwing (practice oviposition)

October 15, 2017

This gallery — named “practice oviposition” (egg-laying) — features a six-photo time series of a female Great Spreadwing damselfly (Archilestes grandis).

Female Great Spreadwing damselflies, like all female odonates, have two cerci (sing. cercus), superior appendages that have little or no function. Also notice two styli (sing. stylus), structures that serve as sensors (like “curb feelers“) in egg positioning during oviposition.

(See a full-size version of the original photo, without annotation.)

The female uses her styli to guide the ovipositor into position, as shown in the next two photos.

In this case, I saw no evidence that the ovipositor actually penetrated the tree twig. I think this was a practice run in preparation for the real thing, as the title of this blog post says.

Copyright © 2017 Walter Sanford. All rights reserved.

Great Spreadwing damselfly (female)

October 13, 2017

A Great Spreadwing damselfly (Archilestes grandis) was spotted near a vernal pool at a remote location in Huntley Meadows Park, Fairfax County, Virginia USA.

This individual is a female, as indicated by her terminal appendages and external reproductive anatomy, including two styli and an ovipositor.

Sometimes I struggle to choose between two similar images, so I decided to post both photos.

The following photo captured the “feel” of the morning light especially well.

The next two photos are among my favorites in this set.

This female was a more cooperative model after she moved to a perch on a man-made brush pile that provides habitat and shelter for many types of animals.

Female Great Spreadwing damselflies, like all female odonates, have two cerci (sing. cercus), superior appendages that have little or no function. Also notice two styli (sing. stylus), structures that serve as sensors (like “curb feelers“) in egg positioning during oviposition.

My next blog post will feature a six-photo time series that I named “practice oviposition” (egg-laying).

Copyright © 2017 Walter Sanford. All rights reserved.

Time to mate (Fall 2017)

October 11, 2017

I speculate Blue-faced Meadowhawk is an arboreal species of dragonfly that returns to the ground/water when it’s time to mate.

A mating pair of Blue-faced Meadowhawk dragonflies (Sympetrum ambiguum) was spotted near a drainage ditch alongside a vernal pool at a remote location in Huntley Meadows Park, Fairfax County, Virginia USA. This pair is “in wheel“: the male is on top; the female on the bottom. The female is a heteromorph, as indicated by her tan coloration.

All dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back: male dragonfly secondary genitalia, called hamules, are located in segments two and three (S2 and S3); female genitalia in segment eight (S8). Dragonflies form the mating wheel in order for their genitalia to connect during copulation.

Copyright © 2017 Walter Sanford. All rights reserved.

Blue-faced Meadowhawk dragonflies

October 9, 2017

“Target(s) acquired. Shots fired!” That’s my generic field report after a successful odonate hunting excursion. Usually I have an idea of the target species I hope to see every time I go photowalking. Shadow Darner dragonfly, Great Spreadwing damselfly, and Blue-faced Meadowhawk dragonfly were the target species for a recent trip to a favorite hotspot where all three types of odonates can be found.

Several Blue-faced Meadowhawk dragonflies (Sympetrum ambiguum) were spotted near a vernal pool at a remote location in Huntley Meadows Park, Fairfax County, Virginia USA.

Both individuals featured in this blog post are male, as indicated by their terminal appendages and turquoise-colored faces.

Blue-faced Meadowhawk is classified as a fall species of odonate. In the mid-Atlantic United States, meadowhawks seem to disappear for several months after they emerge during early summer and reappear during fall. Where do they go? No one knows for sure. I speculate Blue-faced Meadowhawk is an arboreal species of dragonfly that returns to the ground/water when it’s time to mate.

Consistent with my speculation, Blue-faced Meadowhawk seems to prefer habitats where standing water is found near the forest, such as the small vernal pool located at a clearing in the forest at Huntley Meadows Park. Be on the lookout for Blue-faced Meadowhawk everywhere you find similar habitat.

Copyright © 2017 Walter Sanford. All rights reserved.

Should I stay or should I go?

October 7, 2017

Two Common Green Darner dragonflies (Anax junius) were observed flying back-and-forth over a field alongside a vernal pool at a remote location in Huntley Meadows Park (HMP), Fairfax County, Virginia USA — typical feeding behavior for Common Green Darners. Sometimes they would land briefly, perching in shady hidey-holes in the thick vegetation covering the ground. I followed one of the two to a couple of perches.

This individual was very skittish! I was able to shoot one photo at the first perch…

03 OCT 2017 | HMP | Common Green Darner (female)

…and another photo at the last perch. The dragonfly flew toward the tree canopy when I tried to move a step closer.

03 OCT 2017 | HMP | Common Green Darner (female)

It’s relatively easy to identify this type of dragonfly to the species level.

The easiest field mark for identification of a Common Green Darner is that “bull’s eye” on the back of the head. No other [odonate] has it. Source Credit: John Gregoire, Kestrel Haven Wildlife Sanctuary.

On the other hand, it can be more challenging to identify the gender.

Several field markers can be used to identify the gender of this dragonfly. The cerci (sing. cercus) of female Common Green Darners look like almonds, both in color and shape. Two more field markers verify this specimen is female.

Note the brown stripe extending onto abdominal segment 2. Segment 2 [S2] is typically all pale on males. Also [viewing the second photo at full resolution and zooming in on the head] the rear margin of the occiput is not straight. Females have blunt dark colored “teeth” back there which makes the margin look wavy. Source Credit: Ed Lam, author and illustrator of Damselflies of the Northeast, Northeast Odonata Facebook group.

Common Green Darner is one of at least five major species of dragonflies known to be migratory in North America. It’s possible the two Common Green Darners that I observed stopped at Huntley Meadows Park in order to “refuel” before continuing their southward migration.

Related Resources

Copyright © 2017 Walter Sanford. All rights reserved.

You know it’s fall when…

October 5, 2017

mature adult Autumn Meadowhawk dragonflies (Sympetrum vicinum) are seemingly everywhere there is water. Several Autumn Meadowhawks were spotted recently near a vernal pool at a remote location in Huntley Meadows Park (HMP), Fairfax County, Virginia USA.

The first individual is a male, as indicated by his terminal appendages.

03 OCT 2017 | HMP | Autumn Meadowhawk (male)

The last individual is a female, as indicated by her terminal appendages, noticeably thicker abdomen, and coloration.

03 OCT 2017 | HMP | Autumn Meadowhawk (female)

Autumn Meadowhawk is classified as a fall species of odonate. In the mid-Atlantic United States, meadowhawks seem to disappear for several months after they emerge during early summer and reappear during fall. Where do they go? No one knows for sure. I speculate Autumn Meadowhawk is an arboreal species of dragonfly that returns to the ground/water when it’s time to mate.

Related Resource: More previews of coming attractions, a blog post by Walter Sanford.

Copyright © 2017 Walter Sanford. All rights reserved.

Lentic and lotic

October 3, 2017

Doesn’t this idyllic place look like ideal habitat for lotic species of odonates? It is!

Lotic refers to flowing water, from the Latin lotus, washed. … Lotic ecosystems can be contrasted with lentic ecosystems, which involve relatively still terrestrial waters such as lakes and ponds. Source Credit: River ecosystem, Wikipedia.

The preceding photo shows the stream crossing at Popes Head Creek, Hemlock Overlook Regional Park, Fairfax County, Virginia USA (facing downstream toward Bull Run). Both streams provide ideal habitat for many species of dragonflies and damselflies that prefer flowing water rather than still water.

Tech Tip: I used my Panasonic Lumix DMC-ZS150 superzoom camera to shoot the landscape photo featured in this blog post. The camera was set for manual focus at the hyperfocal distance for an aperture of f/4, based upon the instructions provided in the excellent video tutorial by Graham Houghton, “Panasonic Lumix FZ camera easier manual focus method — super point-and-shoot tip.”

Copyright © 2017 Walter Sanford. All rights reserved.

The ugly side of Mother Nature

October 1, 2017

A Big Bluet damselfly (Enallagma durum) was spotted during a photowalk along Deephole Point Road at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA. This individual is a male, eating a teneral damselfly.

10 SEP 2017 | Occoquan Bay NWR | Big Bluet (male, eating prey)

I think they may both be Big Bluets. Source Credit: Michael Moore, Virginia Odonata Facebook group.

Some species of odonates are cannibals, that is, they feed on their own species. And there it is — the ugly side of Mother Nature!

Copyright © 2017 Walter Sanford. All rights reserved.


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