Arachnids 2, Odonates 0

A spider was observed preying upon a teneral damselfly at a vernal pool in Huntley Meadows Park. The genus/species of the spider is uncertain; the damselfly appears to be a female Slender Spreadwing (Lestes rectangularis).

31 MAY 2016 | Huntley Meadows Park | spider preying upon damselfly

According to experts on the BugGuide Facebook group, the spider is probably an unknown species from the Family Araneidae (Orb Weavers).

Post Update: Ashley Bradford, a local arachnid expert and excellent all-around amateur naturalist, identified the spider as an Arabesque Orbweaver (Neoscona arabesca). Thanks, Ashley!

31 MAY 2016 | Huntley Meadows Park | spider preying upon damselfly

Aperture Priority mode was used for the next photo, in order to increase the depth of field. As you can see, the depth of field at f/8.0 was insufficient for both the damselfly and spider to be in focus.

31 MAY 2016 | Huntley Meadows Park | spider preying upon damselfly

A dragonfly was trapped in a spider web at Hidden Pond, Meadowood Recreation Area, Fairfax County, Virginia USA. The dragonfly, possibly an immature male Blue Dasher (Pachydiplax longipennis), is infested with parasitic red water mites.

22 JUN 2016 | Meadowood Recreation Area | dragonfly in spider web

Copyright © 2017 Walter Sanford. All rights reserved.

Eastern Pondhawk dragonflies (mating pair)

21 JUN 2016 | MRA | Eastern Pondhawk (mating pair, “in wheel”)

A mating pair of Eastern Pondhawk dragonflies (Erythemis simplicicollis) was spotted along the earthen dam at Hidden Pond, Meadowood Recreation Area. This pair is “in wheel“: the male is on the upper-right; the female is on the lower-left.

Eastern Pondhawks mate quickly.

Copulation brief (averages 20 sec) and aerial, may be followed by resting period. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Location 10228). Princeton University Press. Kindle Edition.

The mating pair was in wheel when they landed. I was able to shoot one photo before they finished copulating!

Look closely at the full-size version of the preceding photo. Notice the female is infested with parasitic water mites on the underside of her abdomen.

Copyright © 2016 Walter Sanford. All rights reserved.

Unusual viewpoints

A single Halloween Pennant dragonfly (Celithemis eponina) was spotted in a field located near Dogue Creek, Huntley Meadows Park (HMP). This individual is a female, as indicated by its coloration and terminal appendages; no males were spotted during the photowalk.

10 JUL 2015 | HMP | Halloween Pennant (female)

The photos in this set were taken on a very windy day. The wind was blowing so hard the dragonfly struggled to hold onto her perch, as shown in the next photo when the pennant was almost flipped upside-down.

Notice the dragonfly has a mild infestation of parasitic black water mites.

10 JUL 2015 | HMP | Halloween Pennant (female)

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

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

• Genus Celithemis | Celithemis eponina | Halloween Pennant | female | top view
• Genus Celithemis | Celithemis eponina | Halloween Pennant | female | side view
• Genus Celithemis | Celithemis eponina | Halloween Pennant | male | top view
• Genus Celithemis | Celithemis eponina | Halloween Pennant | male | side view

Copyright © 2015 Walter Sanford. All rights reserved.

Parasitic water mites

Chiggers and ticks parasitize human odonate-hunters sometimes; water mites parasitize odonates sometimes. In my experience, some species of dragonflies seem to be more likely to be infested with water mites than others.

Lentic, slow moving water, ponds and temporary water are what mites need for their life cycle. The mites get onto late stage [odonate] nymphs, and then emerge with the nymph. As it ecloses the mites transfer to the adult damselfly, dragonfly. Life cycles of mite and host must be at stages where this can happen, so only certain species would probably be emerging at those times. Species that emerge earlier or later in the season probably wouldn’t have to deal with them. There’s more than one species of mite, so different species would emerge at different times. There is some reference in Corbet’s book [Corbet, Phillip S. (1962). A Biology of Dragonflies.] about some (grooming) species grooming themselves better, and knocking them off also, so they’ve evolved to attach to species where their life cycle can be completed. Some of these species disperse them well also. Nature is truly amazing! Source Credit: Stick LaPan, Northeast Odonata Facebook group.

Odonates and parasitic water mites are able to co-exist except in cases of extreme infestation, when parasitization can be fatal.

A Halloween Pennant dragonfly (Celithemis eponina), spotted in a remote location at Huntley Meadows Park, has a mild infestation of black water mites. This individual is a female, as indicated by its coloration and terminal appendages.

29 JUN 2015 | Huntley Meadows Park | Halloween Pennant (female)

The next photo shows the same female with another water mite attached to the underside of its abdomen.

29 JUN 2015 | Huntley Meadows Park | Halloween Pennant (female)

Another Halloween Pennant dragonfly, spotted at the same remote location 12 days earlier, has an infestation of red water mites. This individual is an immature male, as indicated by its coloration (similar to a female) and terminal appendages.

17 JUN 2015 | Huntley Meadows Park | Halloween Pennant (immature male)

A Blue Dasher dragonfly (Pachydiplax longipennis), spotted along the boardwalk in the central wetland area at Huntley Meadows Park, has an infestation of black water mites. This individual is a male, as indicated by its blue coloration and terminal appendages. He is perching in the obelisk position, thought to be a method of thermoregulation.

16 JUL 2012 | Huntley Meadows Park | Blue Dasher (male)

Copyright © 2015 Walter Sanford. All rights reserved.

Blue Dasher dragonfly (male, obelisking)

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.

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