An Attention Grabbing Dragonfly: Swamp Darners Catch More Than Prey
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There are themes that repeat in our visits and conversations together that reinforce the wonder and amazement found in the fields, forests, creeks, and ponds of Harmony Hill. Part of us sharing these recurring themes is the shear giddiness we find in the gifts of Mother Nature. But a bigger portion of it is that we want you to seek the same joy in the species, the connections, and the beauty found around you, wherever you might be. Your very own backyard, a neighborhood or state park, or any public greenspace can be a Harmony Hill where you uncover the mysteries of delicate spring wildflowers, melodic bird songs, the process of insect metamorphosis, or the intricacies of the web of life.
Just last week, we talked about a species of butterfly, taking to the air in beautiful flight. You’ve likely noticed we can talk for lengthy periods about birds. And if you stay with us as we continue these regular visits, we’re going to spotlight bats, the only mammals capable of sustained, powered flight. There is no doubt whatsoever that we are enthralled by all things with wings.
Today, we’d like to talk about another winged species; but not one with the immediately recognized loveliness of a butterfly or feathered features of a bird.
Any amount of time on the creekbanks or around the edges of the pond here in the spring and summer includes sharing the space with the darting, dashing, and diving of dragonflies. We are blessed with quite a variety of species, with colors and patterns that cover nearly every shade found in rainbows that arch across the sky following an afternoon summer shower. We’ll be talking about more species down the road, but one of the largest dragonflies we have at Harmony Hill is taking to the skies and their impressive size catches our attention. And we think they’ll fascinate you just as much as they do us.
Most of the dragonflies we see during our time outside are a couple of inches in length, with about the same size wingspan. But there is a much bigger species that is regularly found in open areas near the waters of Harmony Hill. There is a fairly common species that can reach around 4” in length, with a wingspan that can exceed that measurement and a body that is strong and heavy in appearance. The Swamp Darner (Epiaeschna heros) will grab your attention if it ever zooms near you, if for no other reason by its size!
Even its scientific name alludes to the how much bigger it is than most dragonflies. Epiaeschna means “in addition to” Aeschna, which is itself a genus containing many species of dragonflies. (As an aside, Aeschna means unattractive or ugly… and we totally disagree with any assessment that dragonflies are ugly!) The species name of “hero” is a word we are all familiar with, as it means a protector and demi-god. For the Swamp Darner, it is another nod to just how big individuals are, as any dragonfly this large might have the blood of some mythological deity.
Dragonflies, along with their close relatives, the Damselflies, are in the Order Odonata, meaning “jaw toothed”. True to that name, they used their strong mouths to devour prey at all stages of their lives. (And, no, they don’t really have teeth. But, if you’ve ever gotten an up-close look at their mouths, you know just how big they are in proportion to the rest of their faces, and you get an idea of just how those strong jaws can chew on the bodies of prey.)
Remember the stages of metamorphosis we learned in elementary school science? How some species of insects undergo various types of metamorphosis, with three types of metamorphosis being recognized by scientists. Depending upon the life stages throughout the process, an insect may be seen as undergoing Ametabolous (little to no metamorphosis), Hemimetabolous (gradual or simple metamorphosis), or Holometabolous (complete metamorphosis) types of metamorphosis. Most of this is revisiting things we all learned in elementary, middle, and high school, and even reviewed in the early days of Biology 101 in college. But if you’d like to take some time to focus more on metamorphosis, we can make that the topic of a future visit. No matter how many times we talk about it, it still amazes us that species change quite drastically from one stage of life to another!
Like other members of the Odonata order, Swamp Darners undergo Hemimetabolous, or gradual, metamorphosis. In that lifespan, an individual Swamp Darner will pass through an egg stage, a nymph (actually a Naiad) stage, and an adult stage. Most darners in our area will have more than one generation each year and Swamp Darners are no exception. Depending upon the weather, it may not be unusual to have up to three generations of Swamp Darners in a year at Harmony Hill.
In the spring, the naiad stage Swamp Darners in the waters of Harmony Hill emerge and molt into their adult stages. The time in which they do this varies on the calendar, but it coincides when springtime low temperatures regularly stay above about 50F degrees. The new adults take to the air with a sense of urgency, as they must reproduce within the limits of an adult stage that will only last between 4 - 8 weeks. With intense pressure from predators ranging from birds and fish to frogs and bats, their lives may very well be even shorter than that!
Once the adults reproduce, the females quickly lay eggs, with protective males actively watching over their territories. The second generation is underway, as the next egg and naiad stages might only last days or weeks. Unlike some species whose females lay eggs directly in water, Swamp Darner females lay their eggs near the water, in damp locations. Females have been observed laying eggs in the mud, in the cervices of fallen trees near the water or, in what may surprise many, inside the top layer of plant tissue or tree bark near water. You see, female Swamp Darners have ovipositors that are perfectly capable of slicing into and penetrating some plant material in order to lay their eggs. Eggs laid in this fashion usually hatch in the dampness of the environment in which they are laid. Some eggs may lay dormant until rehydrated by rains or rising water levels. Once hatched, the naiads will make their way into the water to complete this stage.
Once those naiads are ready to crawl out and molt into the second adult Swamp Darners of the year, the cycle of finding a mate and preparing for the third generation begins.
Let’s take a second and talk about this time as an adult. We just mentioned that adult male Swamp Darners, like many other species of dragonflies, establish, and defend a territory. While some dragonfly males patrol their territory, Swamp Darner males prefer to perch and watch over their area. An insect with a brain so small and simple in appearance that many would not recognize it as an organ capable of any complex neurological activity is, in fact, capable of far more than most would ever expect! Swamp Darners are capable of filtering out motion to focus on visual cues for potential prey and potential threats from predators and other members of their own species. Males are capable of setting up a defined territory, with appropriate habitat for attracting females for laying eggs and finding enough prey to capture. And both males and females are capable of navigating during a migration before setting the third generation into motion!
Now is the time when we pause and encourage you to think about what we just said! An insect with a head that is roughly the size of an adult human pinky fingernail can navigate, behave territorially, and can track targets that equate to us following a baseball traveling around 125 miles per hour! (Sometimes all at the same time!)
The third generation of naiads for the year will overwinter in the waters here, actively hunting for most of the days, weeks, and cooler months of winter.
At all periods of its nymph and adult stages, Swamp Darners are veracious hunters that will capture and devour whatever prey items it can chew and eat. As a naiad, that is usually found in the form of other aquatic invertebrates swimming and crawling in the waters around it. As an adult, that is any invertebrate it can catch on the wing and nibble away on. Their diet includes mosquitoes, flies, yellowjackets, horseflies, other dragonflies (including other Swamp Darners), and even the occasional spider, beetle, or ant.
Well now… we told you we are fascinated by all things with wings and this visit has certainly found us covering all sorts of topics as we discuss a dragonfly that always catches our attention! Large, beautiful, and, as it turns out, smarter than most people give them credit for, the Swamp Darner is more than a flying tank of an insect. It is a multigenerational resident each year at Harmony Hill, and it is an important part of our natural management of mosquitoes and other flying pests. They may not have the stylish, scaly wings of a butterfly and they may not sing the lovely songs of birds, but they are absolutely a valued and revered flier in the airspace in and around Harmony Hill.