Posts Tagged 'dragonflies'



Of Wings and Stigmata

Found the remains of a dragonfly on a Brooklyn sidewalk recently. Possibly a Common Green Darner, one of our most common species. One of the hind wings was still in pretty good shape.Pretty good, but at 40X showing some wear and tear. These two shots are hand-held through the microscope, so not as great as I’d like them, but certainly passable. And the leading edge. I was surprised to see how rough it looks, with regularly spaced thorn-like structures. But I shouldn’t have been. We think of the aerodynamic as streamlined, but this is old school thinking, from the Art Deco in Space, a.k.a. Jetsons, Era. We now know, from things like bird feathers, that a rough surface actually works better for flight.

The dark yellowish bit here the pterostigma, sometimes called simply the stigma, and yes, stigmata in the plural. (See first image for location: on front edge of the upper left). This is a thickened, pigmented cell. A number of other insects have these, but they are most obvious on dragonflies, some of our biggest-winged insects. The stigmata have greater mass than similar-sized sections of the wing. They seem to be a kind of ballast, helping with flight stabilization. Odonates are extraordinary fliers. See here for more detail: “By passive, inertial, pitch angle control, the pterostigma probably makes the wing beat more efficient in slow and hovering flight of small insects, while its raising of the critical flight speeds probably is of more importance to larger insects.”

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…

More Insects

The Common Sootywing. The Kaufman guide says “flight is slow and close to the ground” but I beg to differ with the first characterization. This was about the tenth I’ve seen in various places before I could get a photo.Black Swallowtail, another mover, if not shaker.This is a Great Blue Skimmer, another case where the description of the adult male gives us the common name. This is the female. This photo makes her look smaller than in real life. The larval Asian Ladybug (they seem to have dropped the “multicolored” in the common name; what’s distinguishing about them is that they are variably spotted in the adult form).

No photo, but on 6/2 I spotted a Two-spotted Ladybug in the same Brooklyn Bridge Park patch I first found them in in 2012. I also wrote about them for Humans & Nature.

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…

Darning (?)

Common Green Darner dragonflies (Anax junius).
This is a migratory species, one of the first seen in the spring and one of the last seen in the fall as they move up and down North America. Male is grasping the female as she oviposits, laying her eggs in the lake in Woodlawn Cemetery. Not all Odonata do it this way: in some species, the female will be on her own; in some, the male will be patrolling nearby; and, in some species, as these, the male will continue to stay attached after fertilization.

So far, the only other Odonata action I’ve seen in NYC this season have been a couple of big blue darners of some kind patrolling a sunny path filled with Diptera at Jamaica Bay. They did not pause for photographs. Word on the street is that there are an extraordinary number of dragonflies around the NYC metropolitan area; evidently northwest winds created an unusual fallout situation yesterday. I’ll to keep my eyes open today.

***
Going to use my pulpit here to print this NYC City Council Resolution (No. 864). Wordy, aspirational (what the last sentence actually means isn’t addressed), but this gives a good sense of the interconnected challenges largely going unmet here in the wealthiest city in the country, not to mention the rest of the nation. Contact your council member to get it passed.

Resolution declaring a climate emergency and calling for an immediate emergency mobilization to restore a safe climate.

By Council Members Kallos and Constantinides

Whereas, On April 22, 2016, world leaders from 174 countries and the European Union recognized the threat of climate change and the urgent need to combat it by signing the Paris Agreement, agreeing to keep warming well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C; and

Whereas, On October 8, 2018, the United Nations International Panel on Climate Change (“IPCC”) released a special report, which projected that limiting warming to the 1.5°C target this century will require an unprecedented transformation of every sector of the global economy over the next 12 years; and

Whereas, On November 23, 2018, the United States Fourth National Climate Assessment (“NCA4”) was released and details the massive threat that climate change poses to the American economy, our environment and climate stability, and underscores the need for immediate climate emergency action at all levels of government; and

Whereas, According to the National Aeronautics and Space Administration (NASA)’s Goddard Institute for Space Studies (GISS), global temperatures in 2018 were .83°C (1.5°F) warmer than the 1951 to 1980 mean, and the past five years are collectively the warmest in modern history; and

The death and destruction already wrought by climate change demonstrates that the Earth is already too hot for safety, as attested by increased and intensifying wildfires, floods, rising seas, diseases, droughts and extreme weather; and
Whereas, World Wildlife Fund’s 2018 Living Planet report finds that there has been 60% decline in global wildlife populations between 1970 and 2014, with causes including overfishing, pollution and climate change;

Whereas, According to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, human activity has already severely altered 40% of the marine environment, 50% of inland waterways, and 75% of the planet’s land, and it is projected that half-to-one million species are threatened with extinction, many within the next few decades; and

Whereas, The United States of America has disproportionately contributed to the climate and extinction emergencies and has repeatedly obstructed global efforts to transition toward a green economy, and thus bears an extraordinary responsibility to rapidly address these existential threats; and

Whereas, Restoring a safe and stable climate requires transformative societal and economic change on a scale not seen since World War II to reach net zero greenhouse gas emissions across all sectors, to rapidly and safely drawdown or remove all the excess carbon from the atmosphere, to end the 6th mass extinction of species, and to implement measures to protect all people and species from the increasingly severe consequences of climate change; and
Whereas, A sweeping overhaul of the economy that centers on equity and justice in its solutions is vital to our future and must include the following goals: dramatically expand existing renewable power sources and deploy new production capacity with the goal of meeting 100% of national power demand through renewable sources; build a national, energy-efficient, “smart” grid; upgrade every residential and industrial building for state-of-the-art energy efficiency, comfort and safety; eliminate greenhouse gas emissions from manufacturing, agricultural and other industries, including by investing in local-scale agriculture in communities across the country; repair and improve transportation and other infrastructure, and upgrade water infrastructure to ensure universal access to clean water; fund massive investment in the drawdown of greenhouse gases; make “green” technology, industry, expertise, products and services a major export of the United States, with the aim of becoming the international leader in helping other countries become greenhouse gas neutral economies and bringing about a global transition; and

Whereas, Marginalized populations in New York City and worldwide, including people of color, immigrants, indigenous communities, low-income individuals, people with disabilities, and the unhoused are already disproportionately affected by climate change, and will continue to bear an excess burden as temperatures increase, oceans rise, and disasters worsen; and
Whereas, Addressing climate change fairly requires a “Just Transition” from fossil fuels to clean, renewable energy that is ecologically sustainable and equitable for all people, especially those most impacted by climate change already and those who will be most impacted in the future; and

Whereas, Core to a Just Transition is equity, self-determination, culture, tradition, deep democracy, and the belief that people around the world have a fundamental human right to clean, healthy and adequate air, water, land, food, education, healthcare, and shelter; and
Whereas, Just Transition strategies were first forged by a “blue-green” alliance of labor unions and environmental justice groups who saw the need to phase out the industries that were harming workers, community health, and the planet, while also providing just pathways for workers into new livelihoods; and

Whereas, Just Transition initiatives shift the economy from dirty energy that benefits fossil fuel companies to energy democracy that benefits our people, environment and a clean, renewable energy economy, from funding new highways to expanding public transit, from incinerators and landfills to zero waste products, from industrial food systems to food sovereignty, from car-dependent sprawl and destructive unbridled growth to smart urban development without displacement, and from destructive over-development to habitat and ecosystem restoration; and

Whereas, Building a society that is resilient to the current, expected, and potential effects of climate change will protect health, lives, ecosystems, and economies, and such resilience efforts will have the greatest positive impact if the most dramatic potential consequences of climate change are taken into account; and

Whereas, Climate justice calls for climate resilience planning that addresses the specific experiences, vulnerabilities, and needs of marginalized communities within our jurisdiction, who must be included and supported in actively engaging in climate resilience planning, policy, and actions; and

Whereas, Actions to eliminate greenhouse gas emissions and/or drawdown greenhouse gases may be taken in ways that also improve resilience to the effects of climate change, and vice versa; and

Whereas, Climate justice requires that frontline communities, which have historically borne the brunt of the extractive fossil-fuel economy, participate actively in the planning and implementation of this mobilization effort at all levels of government and that they benefit first from the transition to a renewable energy economy; and

Whereas, Fairness demands the protection and expansion of workers’ right to organize as well as a guarantee of high-paying, high-quality jobs with comprehensive benefits for all as the mobilization to restore a safe climate is launched; and

Whereas, Common sense demands that this unprecedented mobilization effort address the full suite of existential ecological threats facing humanity in a comprehensive, integrated and timely fashion; and

Whereas, Nearly 400 cities, districts and counties across the world representing over 34 million people collectively have recently declared or officially acknowledged the existence of a global climate emergency, including Hoboken, Berkeley, Los Angeles, Montgomery County, Oakland, Richmond, and Santa Cruz in the United States, Bristol and London in the United Kingdom and many cities in Australia, Canada, and Switzerland; and

Whereas, New York City, as the largest city in the United States, can act as a global leader by both converting to an ecologically, socially, and economically regenerative economy at emergency speed, and by rapidly organizing a regional just transition and climate emergency mobilization effort; now, therefore, be it

Resolved, The City Council declares a climate emergency and calls for an immediate emergency mobilization to restore a safe climate.

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.

Dragonlets

Actual entomologists often trap their subject specimens. Some dragonflies can’t be identified unless they’re in the hand. Others rarely stop moving. (Red meadowhawks, I’m thinking of you.)Not that “capturing” a dragonfly by camera is easy. The swaying reed, the moving camera, the photographer’s crappy eyesight… When I spot a dragonfly I don’t think I’ve seen before, my heart starts racing. Which is unfortunate in dragonfly season, already hot enough as it is. These were definitely unfamiliar. Nice of them to perch, too!These are all Seaside Dragonlets (Erythrodiplax berenice). The darks ones are male, the yellow female.Look at this patterning! I think this is a variation on the female.Females further south don’t have as much spotting on the wings.

It turns out I’ve seen the females before, on Plumb Beach, which is not far from where I saw these at Marine Park. That first time was under quite different light conditions, though. The jumping yellow here wasn’t imprinted on my eyes the first time.

This species is unusual: they lay their eggs in salt water, so look for them around salt marshes.

* * *

Paine: “Let them call me rebel and welcome, I feel no concern from it; but I should suffer the misery of devils, were I to make a whore of my soul by swearing allegiance to one whose character is that of a sottish, stupid, stubborn, worthless, brutish man.”

Amberwing

Perithemis tenera.

***

I found this, on the carbon bombing of the planet and the fatalism that induces in some, interesting.

Odonata Season

I saw my first living dragonfly outside my windows on Saturday. I’d seen a couple of Common Green Darners here and there during the last few weeks, but spotting an unidentified dragon over 6th Avenue was the real start of the summer flying season for me. On the same day around Green-Wood’s Sylvan Water, I saw just a handful of dragons, but there were at least three species: Common Green Darner, Black Saddlebags, and one of the gliders. I also saw this Familiar Bluet damselfly, also one of just a handful. These were the first damsels I’ve seen this year. Also spotted this exuvia, or shed husk, of the aquatic nymph stage of a dragonfly. Several of the dragonfly species seen at the moment are migratory, but some are local breeders.


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