Posts Tagged ‘Family Aeshnidae’

What’s my gender?

November 1, 2016

The following Common Green Darner dragonfly (Anax junius) was spotted near a vernal pool in a remote location at Huntley Meadows Park.

Can you identify its gender? You may want to refer to Sexing Common Green Darner dragonflies, my last blog post, before choosing an answer.

Whatever its gender, this individual is what I call a “freshie,” that is, an odonate that emerged recently but may not fit the strict definition of “teneral.” You could call the dragonfly either “post-teneral” or “immature” but it’s definitely not mature, as indicated by the light tan eye color.

Editor’s Note: The dark stripe extending into S2 is the most obvious field marker indicating this dragonfly is female.

Copyright © 2016 Walter Sanford. All rights reserved.

Sexing Common Green Darner dragonflies

October 30, 2016

Several field marks can be used to identify the gender of female and male Common Green Darner dragonflies (Anax junius).

Female

The following individual, spotted at Huntley Meadows Park, is a female. Female dragonflies have a pair of cerci (superior appendages) that have little or no function. The cerci (sing. cercus) of female Common Green Darners look like almonds, both in color and shape.

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

Two more field marks 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 at full resolution, 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.

Male

Male dragonflies have three terminal appendages, collectively called “claspers,” that are used to grab and hold female dragonflies during mating: an upper pair of cerci (“superior appendages”); and a lower unpaired epiproct (“inferior appendage”).

The cerci of male Common Green Darners are slightly darker in color and somewhat thicker and more rounded than the cerci of females of the same species. There are points at the tips of the two male cerci, as shown clearly in the full-size version of the following photo; female cerci are pointless, both literally and figuratively.

Male Common Green Darners have a very short epiproct that is used to grip the “teeth” on the back of head of females of the same species.

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

The individual in the preceding image is an immature male, as indicated by the purple coloration on his abdomen. As a mature male, his abdomen will be partially covered by blue pruinescence like the one shown below.

Related Resources: Digital Dragonflies, presenting high-resolution digital scans of living dragonflies.

  • Genus Anax | Anax junius | Common Green Darner | female | top view
  • Genus Anax | Anax junius | Common Green Darner | female | side view
  • Genus Anax | Anax junius | Common Green Darner | male | top view
  • Genus Anax | Anax junius | Common Green Darner | male | side view

Compare and contrast the cerci of female and male Common Green Darners by viewing the full-size versions of the preceding top views for both sexes and Ed Lam’s excellent composite image, shown below.

ed-lam_cgd_male-vs-female

Composite image used with permission from Ed Lam.

Copyright © 2016 Walter Sanford. All rights reserved.

Shadow Darner dragonfly (female)

October 18, 2016

A Shadow Darner dragonfly (Aeshna umbrosa) was spotted during a photowalk at Mulligan PondJackson Miles Abbott Wetland Refuge (JMAWR).

A Shadow Darner dragonfly (Aeshna umbrosa) spotted at Mulligan Pond, Jackson Miles Abbott Wetland Refuge, Fairfax County, Virginia USA. This individual is a female heteromorph.

14 OCT 2016 | JMAWR | Shadow Darner (female heteromorph)

This individual is a mature female, as indicated by her coloration, rounded hindwings (near abdomen), and terminal appendages. Female Shadow Darners are polymorphic; this one is a female heteromorph, as indicated by her brown eyes and duller coloration than males of the same species.

A Shadow Darner dragonfly (Aeshna umbrosa) spotted at Mulligan Pond, Jackson Miles Abbott Wetland Refuge, Fairfax County, Virginia USA. This individual is a female heteromorph.

14 OCT 2016 | JMAWR | Shadow Darner (female heteromorph)

The following annotated image illustrates some parts of the reproductive anatomy of a female Shadow Darner dragonfly, including an ovipositor for egg-laying and two styli (sing. stylus), structures that serve as sensors in egg positioning.

A Shadow Darner dragonfly (Aeshna umbrosa) spotted at Mulligan Pond, Jackson Miles Abbott Wetland Refuge, Fairfax County, Virginia USA. This individual is a female heteromorph. [Good view of ovipositor/styli.]

14 OCT 2016 | JMAWR | Shadow Darner (female heteromorph)

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

Both female and male Shadow Darners have two long, petal-like cerci (sing. cercus). Notice the female (shown above) is missing both cerci.

[Female] Cerci rounded at tip, longer than S9–10, usually broken off at maturitySource Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Location 4604). Princeton University Press. Kindle Edition.

In contrast, the following male has both cerci and an epiproct; the three terminal appendages are collectively called “claspers.” Claspers are used to grab and hold female damselflies during mating.

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

Related Resources: Scanned digital images from Western Odonata Scans in Life.

  • Shadow Darner | Aeshna umbrosaheteromorph female
  • Shadow Darner | Aeshna umbrosaheteromorph female (note very tattered wings of this old individual)
  • Shadow Darner | Aeshna umbrosaandromorph female
  • Shadow Darner | Aeshna umbrosamale (typical “A. u. umbrosa” with small green abdominal spots but nowhere near the range of that subspecies!)

Copyright © 2016 Walter Sanford. All rights reserved.

Swamp Darner dragonfly (female, oviposition)

April 27, 2016

The cavalcade of spring species of odonates continues: a first-of-season Swamp Darner dragonfly (Epiaeschna heros) was spotted on 25 April 2016 near a vernal pool at a remote location in Huntley Meadows Park.

A Swamp Darner dragonfly (Epiaeschna heros) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a female, laying eggs (oviposition) in soft wood.

This individual is a female, laying eggs (oviposition) in soft wood. All female damselflies and many female dragonflies, especially Aeschnidae, have an ovipositor that is used to puncture aquatic plants, logs, wet mud, etc.; eggs are placed singly in the puncture. The ovipositor is clearly visible in the following annotated image.

A Swamp Darner dragonfly (Epiaeschna heros) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a female, laying eggs (oviposition) in soft wood.

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

Related Resource: Swamp Darner Ovipositing in Rotting Log (NJ, USA), an excellent YouTube video (2:03) published on June 5, 2014, shot from the edge of a vernal pool located in New Jersey.

Copyright © 2016 Walter Sanford. All rights reserved.

Swamp Darner dragonfly (female, oviposition)

January 23, 2015

The following photos show a Swamp Darner dragonfly (Epiaeschna heros) spotted on 23 May 2014 near a vernal pool in a relatively remote location in the forest at Huntley Meadows Park. This individual is a female, shown laying eggs (oviposition) in a muddy drainage ditch.

All female damselflies and many female dragonflies, especially Aeschnidae, have an ovipositor that is used to puncture aquatic plants, logs, wet mud, etc.; eggs are placed singly in the puncture. The ovipositor is clearly visible in all of the following photos.

Swamp Darner dragonfly (female, oviposition)

Swamp Darner dragonfly (female, oviposition)

Swamp Darner dragonfly (female, oviposition)

Swamp Darner dragonfly (female, oviposition)

Related Resources: Digital Dragonflies, presenting high-resolution digital scans of living dragonflies.

  • Genus Epiaeschna | Epiaeschna heros | Swamp Darner | female | top view
  • Genus Epiaeschna | Epiaeschna heros | Swamp Darner | female | side view

See also Swamp Darner Ovipositing in Rotting Log (NJ, USA), an excellent YouTube video published on June 5, 2014, shot from the edge of a vernal pool located in New Jersey.

Copyright © 2015 Walter Sanford. All rights reserved.

Swamp Darner dragonfly (female, oviposition)

June 19, 2014

I spotted a Swamp Darner dragonfly (Epiaeschna heros) during a photowalk at Huntley Meadows Park on 02 June 2014. This individual is a female, shown laying eggs (oviposition) in mud alongside a vernal pool.

Richard Orr, renowned expert on odonates of the mid-Atlantic region, shared several interesting factoids about Darners and Swamp Darners during “Advanced Dragonfly Studies,” a recent Audubon Naturalist Society Adult Class and Field Trip:

  • Petaltails (Petaluridae) were once thought to be the oldest family of dragonflies; recent genetic studies have shown that Darners (Aeshnidae) are the most primitive family.
  • Darners have the most complex compound eyes in the insect world.
  • Swamp Darner eggs can survive for up to a year without water, in case the vernal pool (where the female laid her eggs) evaporates during summer.

All female damselflies and many female dragonflies, especially Aeschnidae, have an ovipositor that is used to puncture aquatic plants, logs, wet mud, etc.; eggs are placed singly in the puncture. The ovipositor is clearly visible in all of the following photos.

Swamp Darner dragonfly (female, oviposition)

Swamp Darner dragonfly (female, oviposition)

Swamp Darner dragonfly (female, oviposition)

Swamp Darner dragonfly (female, oviposition)

Related Resources: Digital Dragonflies, presenting high-resolution digital scans of living dragonflies.

  • Genus Epiaeschna | Epiaeschna heros | Swamp Darner | female | top view
  • Genus Epiaeschna | Epiaeschna heros | Swamp Darner | female | side view

See also Swamp Darner Ovipositing in Rotting Log (NJ, USA), an excellent YouTube video published on June 5, 2014, shot from the edge of a vernal pool located in New Jersey.

Copyright © 2014 Walter Sanford. All rights reserved.


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