Archive for July, 2012

Green Heron (predator-prey)

July 31, 2012

A Green Heron (Butorides virescens), possibly an immature, spotted in the central wetland area at Huntley Meadows Park. This individual was stalking and eating a frog. I have observed the same bird (at least I think it’s the same bird) for two weeks. It seems like the bird has learned frogs like to hide in the shade under the boardwalk. The bird walks along the edge of the boardwalk looking for frogs; when it spots one, it launches itself beak-first like a spear. (Photo 1 shows how the bird’s beak speared the frog.) Next the bird hops onto the boardwalk and repositions the frog until it is holding the frog head first. Then, gulp! Photo 6 is entitled, “I can’t talk … I have a frog in my throat!”

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Photo 1.

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Photo 2.

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Photo 3.

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Photo 4.

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Photo 5.

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Photo 6.

Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com

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Blue Dasher dragonfly (male, obelisking)

July 29, 2012

The following photographs show a Blue Dasher dragonfly (Pachydiplax longipennis) spotted along the boardwalk in the central wetland area at Huntley Meadows Park. This individual is a male, as indicated by its blue coloration and the terminal appendages at the end of its abdomen.

Male dragonflies have three terminal appendages, called “claspers,” including a pair of upper appendages called “cerci” and one lower appendage called an “epiproct.” The Blue Dasher’s cerci are black and are visible in all photos; its epiproct is tan and is visible in Photos 3-4. The male dragonfly’s claspers are used to grab and hold female dragonflies during mating.

The black nodules on the underside of the dragonfly’s thorax, shown clearly in Photo 1, are parasitic water mites.

Water mites (Family Arrenuridae) are a common still-water odonate parasite. They hatch from eggs laid underwater and the larva are free swimming. They seek then attach themselves to odonate larva and when the odonate larva emerges to molt into an adult, the mites transfer to the teneral dragonfly or damselfly. The mites continue to feed on the odonate’s fluids while the dragonfly/damselfly matures. When the odonate returns to water to reproduce, the mites drop back into the water where they continue to develop, undergoing a series of molts, feed on other underwater creatures, mate, and lay eggs. Source Credit: Ed Lam, author and illustrator of Damselflies of the Northeast.

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Some dragonflies, such as Blue Dasher, regulate their body temperature by perching in the “obelisk position”: the tip of the dragonfly’s abdomen is pointed toward the Sun, minimizing the surface area of the body exposed to direct heating by the Sun’s rays, thereby avoiding overheating.

Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com

Blue Dasher dragonflies (mating pair)

July 27, 2012

A mating pair of Blue Dasher dragonflies (Pachydiplax longipennis) was spotted along the boardwalk in the central wetland area at Huntley Meadows Park. The pair is shown “in wheel” in all photos.

All dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back: male dragonfly secondary genitalia are located in segments two and three (2 and 3); female genitalia in segment eight (8). Therefore, the male dragonfly is on top; the female is on the bottom.

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Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com

Great Blue Skimmer dragonfly (female, oviposition, in flight) redux

July 25, 2012

A female Great Blue Skimmer dragonfly (Libellula vibrans) laying eggs by the process of oviposition. The dragonfly skims the water repeatedly, picking up drops of water that are used to flick fertilized eggs toward the shore. The process typically lasts a few seconds to a few minutes.

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This is one of the better dragonflies in flight photos I’ve taken this year: the focus point is centered on the thorax and the subject fills the entire frame with only minor cropping.

Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com

Needham’s Skimmer dragonflies (mating pair)

July 23, 2012

A mating pair of Needham’s Skimmer dragonflies (Libellula needhami) spotted along the boardwalk that goes through the central wetland area at Huntley Meadows Park. The pair is shown “in wheel” in Photos 1-3 (of 4). All dragonflies and damselflies have a 10-segmented abdomen: male dragonfly secondary genitalia are located in segments two and three (2 and 3); female genitalia in segment eight (8). Therefore, the male dragonfly is on top; the female is on the bottom.

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The last photo shows the female half of the pair, resting immediately after copulation with her male partner. Look closely at the full-size version of the photo. Notice the flanges beneath the female’s eighth abdominal segment that are used to scoop water when laying eggs (oviposition).

Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com

Twelve-spotted Skimmer dragonfly (male)

July 20, 2012

A Twelve-spotted Skimmer dragonfly (Libellula pulchella) spotted along the boardwalk that goes through the central wetland area at Huntley Meadows Park. This individual is a male, as indicated by its distinctive pattern of wing spots and the terminal appendages at the end of its abdomen. Notice that the Twelve-spotted Skimmer perches on four of six legs, with the two front legs curled around its head.

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Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com

Slaty Skimmer dragonfly (female, oviposition, in flight)

July 18, 2012

A Slaty Skimmer dragonfly (Libellula incesta) spotted at Huntley Meadows Park. This individual is an adult female, shown in flight as she oviposits eggs in the central wetland area. The title of Photo 2 is, “A dragonfly ‘swimming’ in air.”

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Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com

Great Blue Skimmer dragonflies (mating pair, female ovipositing)

July 16, 2012

The following gallery shows a mating pair of Great Blue Skimmer dragonflies (Libellula vibrans) spotted in the central wetland area at Huntley Meadows Park on 06 June 2012. Photo 1 (of 2) shows the pair “in wheel.” All dragonflies and damselflies have a 10-segmented abdomen: male dragonfly secondary genitalia are located in segments two and three (2 and 3); female genitalia in segment eight (8). Therefore, the male dragonfly is on top in Photo 1; the female is on the bottom. Photo 2 shows the female half of the mating pair, resting immediately after copulation.

The following video shows the same mating pair of Great Blue Skimmer dragonflies (‘in wheel”), and the female resting (after copulation) before laying eggs by the process of oviposition. The female dragonfly skims the water repeatedly, picking up drops of water that are used to flick fertilized eggs toward the shore. The process typically lasts a few seconds to a few minutes. The male half of the mating pair “hover guards” the female as she lays eggs, also known as “non-contact guarding” (see slow motion segment of video).

Copyright © 2012 Walter Sanford. All rights reserved.

Spangled Skimmer dragonfly (immature male)

July 14, 2012

A Spangled Skimmer dragonfly (Libellula cyanea) spotted along the “Hike-Bike Trail” at Huntley Meadows Park. This individual is an immature male, based upon its coloration and the terminal appendages at the posterior of its abdomen.

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Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com

Great Blue Skimmer dragonfly (female, oviposition, in flight)

July 12, 2012

A female Great Blue Skimmer dragonfly (Libellula vibrans) laying eggs by the process of oviposition. Flanges beneath the female’s eighth abdominal segment are used to scoop and hold a few drops of water; the dragonfly skims the water repeatedly, picking up drops of water that are used to flick fertilized eggs toward the shore. The process typically lasts a few seconds to a few minutes. Look closely at the full-size version of this photo — I think you can see a drop of water and/or egg cluster at the lower end of the dragonfly’s abdomen!

Remember that all dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back.

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Tech Tips: I used a shutter speed of 1,300 second in order to capture a still photo of the dragonfly in flight.

Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com


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