Posts Tagged 'damselflies'

Paulson on the Odonata


Dennis Paulson’s new Dragonflies and Damselflies: A Natural History‘s is a great introduction to odonating.

Paulson has written the standard field guides to American/Canadian odes as well as dozens of journal papers on odonates. The pictures in his field guides are too small; that’s these guide’ principal fault. But consider: there are 461 species to be covered in the US and Canada. There is strong sexual dimorphism in odonates, meaning at least two images for each species. Some damselfly species have four or five color forms. Dragonflies and Damselflies of the East is 519 pages long, not including glossary and index. Gotta be some hard calls for the author and publisher in this field of field guide publishing.

This new book, however, is coffee table format. It’s aimed for a popular readership. While there is a Further Resources appendix, I note the absence of a real bibliography. There’s a lot of scientific literature out there; touching base with it would have been a good thing, especially with our unparallelled ability to pull up scientific literature on the ‘net (if not full text than at least the abstract).

Chapters on natural history alternate with two-page spreads on individual species from around the world. At the time of publication, there were 6,299 described odonate species. That number is sure to change. Nearly two hundred of these were first described between 2015-2017. Only a small sample are included here, obviously, representing the great range and diversity of this order of insects.

News to me: the Common Winter Damsel (Sympecma fusca), found in southern and central Europe east to central Asia, stays dormant through the winder. They grab hold of something and sit out the winter in dormancy. The two other species in this genus are the only overwintering adult Odonates we know of. Advantage: very early start to reproduction, before predatory migratory birds show up. Disadvantage: they suffer “moderately high mortality from rodent predation” in winter. A frosted-over damselfly is still fresh meat, after all.

On the Azores, the population of Citrine Forktails (Ischnura hastata) is all female. They’re the only ode that manifests parthenogenesis. With so many species, there are many strategies and adaptations and habitats. The basic plane is the same, but the differences are what fascinates.
The Eastern Pondhawk (Erythemis simplicicollis) rates an entry because it is one of the few species in the world that seems to be increasing its numbers, going against the general decline brought about by… us. I photographed this one in Brooklyn. They thrive in any kind of fresh water; many other species have rather more specific requirements: gravel bottoms, slow moving streams, fast moving streams, muddy bottoms, etc.

What else? Much else. Up to 60% of the weight of a dragonfly is muscle used to power their four wings. “Although they operate independently, the fore- and hindwings interact with one another. The hindwings suffer slightly increased drag owing to the turbulence created in front of them by the forewings, but the positive pressure generated by the hindwings actually decreases drag on the forewings.”

There are even some numbers on flight speed: average speed of a moderate sized dragonfly: 4.5 mph. The largest dragonflies, the darners, can hit bursts of 34mph!
Sweetflag Spreadwing (Lestes forcipatus) female. Photographed in Alley Pond Park in Queens, on the same day as this
Slender Spreadwing (Lestes rectangularis). These are now the only Queens records for Lestes genus spreadwings at Odonata Central. iNaturalist has one more, seen in 2016, but nobody could get it down to species level. I have a similar problem with the third spreadwing I photographed in Ally Pond Park that day. Without the specimen in hand, identification can be impossible, but I’d rather see them flying than tucked into someone’s drawer. Brooklyn, by the way, has only one record of a spreadwing, but here too the picture is too obscure for species-level.

More Exuviae

An emergent damselfly next to the husk of its former, aquatic life stage. When they first emerge as their adult, flying form, they don’t have much color. Their wings unfurl and harden off, like their new exoskeleton. They can’t fly immediately.When they can fly, they will sometimes take shelter in trees, bushes, etc., to finish up. The wings are milky at first, make them look a bit like craneflies in flight. More exuviae. This all happen to be from dragonflies, not damselflies.These all seem to have a good grip, but they are very insubstantial. They’ll blow out of your hand at the hint of a breeze.

Exuviae

Wait… what? This Rambur’s Forktail damselfly is perched on the exuviae of a dragonfly.Another view of the male Rambur’s green-blue color pattern. Dragon- and damselfly eggs are laid on or near water. The larval stage is aquatic. After a season, or a year (or more depending on species and location), the aquatic nymph crawls out of the water, onto a twig, stone, etc. A floating leaf in this case. The adults emerge from these, with wings! The remaining husks of exosleton are called exuviae. These were left by dragonflies: the short wing-like gill structures on the back tell you this. This is what’s left of an aquatic damselfly. The gills are at the end of the abdomen. This is about an inch-long and quite hard to see from up above. There were a lot of dragonfly exuviae around the Sylvan Water the other day, presumably from Eastern Amberwings, which were all over the place. This was the only damselfly exuvia I found, even though there were several adult damselflies flying.And mating…

Three Common Brooklyn Damselflies

In my experience, these are the three most common Brooklyn damselflies. Eastern Forktail male. Beware that Rambur’s Forktail and Furtive Forktail males also have variations on this green thorax/blue end segments coloring. Fragile Forktail male. The broken green lines on the thorax, upside down exclamation points in this case, are unique. Not sure where this “Fragile” name comes from, since I see this species all over the place. Seems like a tough little critter to me.This is a female Forktail — you can just see the exclamation points. Note that the scale is different for all these pictures. The Forktails (Ischnura genus) are small, running from just under an inch to nearly an inch and a half long depending on the species.Here’s a Fragile ovipositing, dipping her abdomen under water to lay her eggs. Familiar Bluet male. Several of the mostly-blue bluets of the Enallagama genus can only really be told apart by their cerci. These are the structures at the end of the abdomen. They use these to grasp females during sex. Only male and females of the same species “fit” together. Attached to him just behind her head, she can bend forward to attach herself to his second abdominal section, the location of his genitalia.Behold, the “wheel” of mating. There are two damselfly nymph husks on this vertical twig. After hatching, damselfly larva become fierce little aquatic predators. They molt as they grow underwater. Given the date these were spotted, early June, these must have overwintered in Sylvan Water before emerging on a warm day to break out as the adult, flying form. See the green eyes of an emerging adult? It will have to harden off and develop some color over the next few hours.Looks like a brand new Fragile Forktail, soon to start clearing the air of tiny insects. (Click all images to fill uyp your screen.)

Odes

Spot-winged Glider, in a rare perch. They can spend hours in the air.Blue Dasher male, quite common and frequently perched.Eastern Pondhawk male.Male Painted SkimmerThis damselfly is peculiar. I can find no matching ID for it, and both iNaturalist and bugguide.net remain silent to my queries. I think it may be a maturing andromorph (that is, male-like) female Eastern Forktail. Lam illustrates six forms of Ischnura verticalis; Paulson pictures five forms. None of their examples are quite this one, though, Bar-winged Skimmer male. A new species for me.

All spotted in either Brooklyn or the Bronx recently. A quick reminder: males are usually patrolling water bodies, which females only visit for mating purposes.And here’s a female Common Whitetail, away from the water…

And the Damsels

Still in Virginia: Female Fragile Forktail (Ischnura posita) depositing eggs.Furtive Forktail (Ischnura prognata) male, a first for me. Such a challenge to photograph these wee critters!And then to ID them! Immediately above and below, a female Familiar Bluet ((Enallagama civile)). (My best guess: iNaturalist and bug guide.net haven’t come through.) The females of this species come in three color forms!Here’s a Familiar Bluet male (above & below).

Enter The Dragons

A trip a few states south results in a preview of the shape of Odonata to come. Emerging adult dragonflies in a small pond. There were about a dozen. Eastern Pondhawks, I think. Once they wiggle out of the husks of their larval forms, they need to harden off, develop their color, stiffen their wings. I’d never seen this in action. It’s slow-going…Meanwhile, in a piney wood a few counties away, a female Blue Corporal (Ladona deplanata) is already up and at ’em. A new species for me. Did not see the male. Often, males dragonflies and damselflies will stake-out and patrol their territories, usually water bodies, while the females are in the distance, only approaching when they’re ready to mate.Painted Skimmer (Libellula semifasciata) glorious in the sun.Immature Common Whitetail (Plathemis lydia) male above and mature male below.


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