Common Green Darners Migrating South
Monarchs aren’t the only insect that are seasonal migrants. The Common Green Darner dragonfly and a few other dragonfly species are as well. However, where Monarchs move northward in the spring over several generations, one generation of Common Green Darners flies all the way from southern U.S., Mexico and the Caribbean in the spring to New England and Canada. Here they lay eggs which give rise to a second generation that migrates south in September and October. Upon reaching their destination they then breed. A third generation emerges around November and lives entirely in the south during winter. It’s their offspring that start the cycle again by swarming northward as temperatures warm in the spring.
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Common Green Darners Mating & Laying Eggs
Darners are a family of dragonflies whose members are quite large (some over three inches in length). Common Green Darners (Anax junius) are one of only two darners in the Northeast with an entirely green thorax (section between head and abdomen). Often you find them perching low in grasses and weeds. Males tend to fly along the shorelines of ponds, patrolling for females and keeping other males at bay.
After mating takes place, the males of some species of dragonflies disappear. In other species, the male stays nearby, guarding the female and fending off other males that might remove the initial suitor’s sperm and replace it with their own. Some species go to the extreme of remaining attached to each other while egg-laying takes place. Common Green Darners are the only species of darner that often lays in this manner – in tandem, with the male still clasping the female while she submerges her abdomen and lays her eggs in aquatic vegetation (pictured).
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Ebony Jewelwings
Damselflies, smaller and more delicate versions of dragonflies, are predatory aerial insects found near streams and wetlands. The male Ebony Jewelwing (Calopteryzx maculata) damselfly is aptly named. Its pure black wings (the only dragonfly or damselfly in the Northeast with entirely black wings) and iridescent green head and abdomen are a striking combination. The female lacks the iridescence of the male and its wings are dark but not quite black, with a distinct white spot (pterostigma) at the outer edge of both forewings.
Ebony Jewelwings only live about two weeks. During much of this time they can be found resting on leaves or branches in sunny spots of the forest, often near the slow-moving stream in which they spent their youth (most dragonfly and damselfly larvae are aquatic).
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“Mating Wheels”
Dragonflies and damselflies both create what are called “mating wheels” when they mate. The male grasps the female at the back of her head with the terminal appendages at the end of his abdomen and the female curls her abdomen forward until the tip of her abdomen reaches the male’s sex organs.
Many male dragonflies go to great lengths to make sure their sperm have reproductive success. Prior to mating they often remove any sperm that happen to be in the female from previous matings. In addition, depending on species, they may leave after mating, fly with and guard the female as she lays her eggs, or remain grasping the female as her eggs are laid. His proximity to the female during egg laying prevents other males from removing his sperm.
Much of this information, as well as excellent photos for identifying dragonflies and damselflies, can be found in A Field Guide to the Dragonflies and Damselflies of Massachusetts, by Burne, Loose and Nikula. Another excellent Odonata resource is Dragonflies and Damselflies of the East by Dennis Paulson. (Photo: Mating darners (fast flying, large dragonflies), male above female)
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Damselflies & Dragonflies Eclosing
It’s time to check emerging vegetation along the shores of ponds for adult damselflies and dragonflies emerging from their larval skins (eclosing). Fully developed aquatic larvae crawl up out of the water onto emergent vegetation and rocks, split the back of their skin and emerge as winged adults.
As the adult slowly pulls itself up and out of its larval skin two things are immediately apparent. Newly eclosed dragonflies and damselflies lack pigment, and they are extremely vulnerable to predation as they hang clutching their old skin, pumping air into their body and liquid into their expanding wings. These newly-eclosed adults must wait in this position, unable to escape predators, until their wings dry and they can fly. (Photo: damselfly eclosing. Note diminutive size of cream-colored wings before they expand.)
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Newly-emerged Dragonflies Vulnerable
When a dragonfly larva crawls up out of the water onto emergent vegetation or a rock to split its skin and emerge as a winged adult, it is in its most vulnerable state, for until its wings are pumped up and dry, it is incapable of flying.
Often for two or three hours a newly-emerged dragonfly will cling to the substrate, pumping hemolymph into its wings until they are fully expanded and then hang there defenseless while its exoskeleton and wings begin to harden. Only then does pigment in the dragonfly’s body become apparent, and its formerly pale, colorless head, thorax, abdomen and wings (see inset) assume their true colors.
The pictured Common Grackle has taken advantage of this precarious stage in a dragonfly’s life cycle and collected several dragonflies to feed to its offspring. The dragonflies’ lack of color indicates that this predation took place while the dragonflies were still flightless and before pigmentation was present.
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Shadow Darners Laying Eggs
The dragonfly family Aeshnidae consists of strong-flying dragonflies called darners, some of which are over three inches in length. The majority of darners reach the peak of their population in August and early September. Male Shadow Darners (Aeshna umbrosa) can be seen patrolling breeding sites a few feet over the water’s surface, searching for females and driving off competing males. Females can be observed repeatedly landing at the base of cattails, inserting their sharp-edged ovipositors and slicing open leaves, where they then deposit their eggs. If you look at the bottom third of cattails at this time of year, near the water’s surface, you will find tiny, tan, vertical slits where dragonfly egg-laying has taken place. (Photo: female Shadow Darner laying eggs)
Common Green Darners Appearing
The Common Green Darner (Anax junius) is one of our most common dragonflies. often seen near ponds. The family of dragonflies known as “darners” consists of species with large eyes and long abdomens that tend to rest infrequently and when they do rest, usually hang vertically. The Common Green Darner is the only North American darner in which the male and female usually fly in tandem when the female is laying her eggs on emergent vegetation.
Up to 50 of the world’s 5,200 dragonfly species migrate and the Common Green Darner is one of them. In the fall most (but not all) adult Common Green Darners migrate south to Florida, eastern Mexico and the West Indies. Huge clouds of migrating dragonflies have been seen along the East Coast, Gulf Coast and the Great lakes in autumn. Transmitters weighing 1/100th of an ounce that have been attached to migrating dragonflies confirm that they migrate much like birds. Just like avian migrators, they build up their fat reserves prior to migrating; they follow the same flyway as birds, along the Atlantic Coast; and like birds, dragonflies don’t fly every day but stop and rest every three days or so.
Some dragonflies mate and lay eggs along the way, while others do so when they reach their destination. The eggs hatch, larvae develop and the adults head north in the spring. Unlike birds, migration is only one-way for dragonflies. It is the offspring of the fall migrating generation that migrate north in the spring. Here in the Northeast, most arrive before any resident Common Green Darners have emerged. (photo: female Common Green Darner)
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Damselfly or Dragonfly?
A visit to a pond will usually include sightings of dragonflies and the more delicate damselflies. Both of these types of insects are in the order Odonata (Greek for “tooth,” referring to the serrated jaws of the adults). They are separated into two suborders, due to their wing shapes and sizes. The wings of dragonflies differ in shape and size (hind wings are broader than forewings), whereas damselfly fore and hind wings are similar in shape, with the hind wings sometimes being smaller.
In addition to wing differences, damselflies have eyes that are separated by more than an eye’s width, whereas dragonfly eyes either touch or are separated by less than an eye’s width. Damselflies are smaller and more slender than dragonflies and perch with their wings closed over their abdomens or held slightly spread. Dragonflies at rest hold their wings out flat or downward. In addition, dragonflies are more powerful and acrobatic in flight than damselflies.
Although these differences distinguish them, damselflies and dragonflies do have many similarities. Both are carnivorous, both spend most of their lives as aquatic larvae, and both lay their eggs in or near water.
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Eastern Newts Dining On Hapless Dragonflies
Inevitably, as newly-emerged drying dragonflies and damselflies hang over the surface of the water on emergent vegetation, breezes blow and some of them lose their grip, falling into the water below. At this stage, their bodies are soft and they are not capable of flight, which leaves them very vulnerable to aquatic predators such as Eastern Newts. While amphibian eggs, aquatic insects, crustaceans, worms and small molluscs make up most of their diet, Eastern Newts are quick to make a meal of most invertebrates that end up in the water.
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Dragonflies Eclosing
The sudden hot weather seems to have triggered a mass emergence of dragonflies and damselflies. The emerging vegetation along the shores of ponds is covered with larval Odonates (members of the order of insects that includes dragonflies and damselflies) metamorphosing into adults. The adults, still in the skin of their last larval stage, crawl out of the water, climb up vegetation, rocks, etc., and split the back of their larval skin. The adult flips backwards out of this opening, hangs upside down and then grasps the vegetation and/or empty larval skin while as its abdomen is released. The dragonfly hangs in the breeze while it pumps air into its body, sending liquid into its wings.
To appreciate this process called eclosion, compare the size of the wings in the photo insert (recently-emerged adult) with those in the larger photograph, which was taken twelve minutes after emergence. Within a day or so the sheen on the newly-formed wings goes away, the dragonfly’s body hardens and colors start to appear.
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Darners Laying Eggs
Females of different species of dragonfly have different techniques for laying their eggs. Most skimmers, cruisers and clubtails dip the tip of their abdomen to the surface of the water while hovering or flying, and release their eggs. Most darners, such as the Shadow Darner (Aeshna umbrosa) pictured, have a sharp-edged ovipositor with which they slit open a stem or leaf of a plant on or near the water. They then push their egg into the plant tissue exposed by the slit. Because they are stationary during this process, female darners are vulnerable to predation by fish and frogs at this time. A close look at the bottom third of cattail leaves this time of year will tell you whether or not darners are in the vicinity, as the slits they make are very apparent, appearing as thin, tan, 1/2″ vertical lines.
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button.
Predator Eating Predator
The Six-spotted Fishing Spider, Dolomedes triton, is an arachnid in the nursery web spider family Pisauridae. As its name implies, the Six-spotted Fishing Spider does occasionally eat small fish, but also consumes other invertebrates and tadpoles. The hunting techniques of fishing spiders are varied. Often they sit patiently during the day, waiting hours with their legs stretched out for an unsuspecting insect (such as the pictured Dot-tailed Whiteface dragonfly) to land on the same lily pad or leaf that the spider is sitting on. They can and do walk on water as well as dive up to seven inches deep in order to catch aquatic prey. The Six-spotted Fishing Spider in this photograph has removed the head of its prey and is drinking its liquefied innards.
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Waxwings Supplementing Sugary Fruit Diet With High-Protein Insects
The diet of both Cedar and Bohemian Waxwings is primarily sugary fruits throughout most of year. Research shows that they can subsist on this diet exclusively for as many as 18 days. However, in winter when feeding on fruits, they also feed on buds and available insects. In warmer months, waxwings will fly out over water from exposed perches, much like flycatchers, and snatch emerging aquatic insects such as mosquitoes, midges, mayflies, caddisflies and dragonflies out of the air. They also glean for vegetation-borne insect prey, such as scale insects. At this time of year they are taking advantage of winter stonefly hatches over open streams. (photos: bohemian waxwing & stonefly)
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Meadowhawks Mating & Laying Eggs
There is a genus of dragonflies, Sympetrum, referred to as meadowhawks, which emerge and fly in late summer and autumn, breeding in ponds and foraging over meadows. Mature males and some females of certain species of meadowhawks become bright red on part or all of their bodies. When breeding, the male grasps his mate behind her head with the appendages at the end of his abdomen and often does not release the female until after she has laid her eggs, which she typically does by dipping the tip of her abdomen in the water (see photo). The reason for this continued connection is related to the fact that a male dragonfly may remove sperm present in the female from any previous mating and replace it with his own packet of sperm, or spermatophore. In order to prevent this from happening, and to assure his paternity, a male dragonfly sometimes flies close to his mate, guarding her while she lays her eggs, or, in the case of meadowhawks, may fly in tandem with the female throughout the egg-laying process.
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Dragonflies Laying Eggs
Never let it be said that Naturally Curious readers aren’t creative thinkers (see guesses on yesterday’s post) ! The vertical slits in the cattail leaves were made by female dragonflies that were in the process of laying their eggs. There are many different egg-laying strategies employed by dragonflies. Many females in the group of large, strong-flying dragonflies known as “darners” (such as the pictured Black-tipped Darner, Aeshna tuberculifera) use their lance-like ovipositors (see photo) to insert eggs into plants stems such as cattail, sphagnum moss, rotting wood or wet soil. However, most species of dragonflies possess non-functional ovipositors. The eggs of many of these species are washed off into water during flight as the female dips the tip of her abdomen into the lake, pond, river or stream.
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Raccoons Quick and Adept Hunters
Not everyone enjoys discovering what an animal eats by dissecting its scat, but for those of us who do, the revelations can be worth the effort. One quick glance at the shape and size of the pictured scat confirmed that a raccoon had been in the vicinity and bits of crayfish exoskeleton in it indicated that the raccoon fed from the nearby pond. Further examination of the contents revealed that raccoons are fast enough to catch dragonflies – something I wouldn’t have necessarily known and most likely wouldn’t observe in the field. Who would have guessed that raccoons are quick enough or interested enough in dragonflies to catch them? (NB: Do not do as I did – do not touch or dissect raccoon scat as it can contain bacteria, ticks and Baylisascaris roundworms which can cause neurological damage.)
As an aside, I thought it might be of interest for readers to know what goes into the making of a Naturally Curious post. The following describes my morning yesterday: out for a walk, visit a pond, see scat on a big, wooden raft that has floated near shore, manage to leap onto raft to take a picture of the scat, photograph scat and then look up to see that my leap has shoved the raft away from the edge of the pond, and I’ve drifted out into the middle of said pond. Balancing the camera on the raft, I paddle, first with one hand and then with both (at one corner), trying to move this 15’ x 15’ wooden structure in the direction I want it to go. Make a little progress, but not much. Beloved chocolate lab swims up to raft, I hold onto her neck and she pulls us to shore, camera intact. And I haven’t even begun to dissect, photograph, label and write about the contents of what led me on this adventure!
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Antlions Trapping Insects
The larvae of a predaceous group of winged insects (family Myrmeleontidae) that closely resemble dragonflies and damselflies are referred to as “antlions” – they have the ferociousness of a lion and prey mainly on ants. The manner in which an antlion traps its prey is ingenious. It excavates a conical pit in sandy soil (an antlion is also called a “doodlebug” because of the squiggly trails it leaves in the sand looking for just the right spot for a pit). Using its head as a shovel, it tosses out sand as it turns in a circle, digging deeper and deeper, until it forms a pit roughly two inches deep and three inches wide. The antlion lies at the bottom of the pit, covered by a thin layer of sand except for it pincer-like mandibles, which are ready to snatch prey at a second’s notice.
The slope of the sides of the pit is at the angle of repose – as steep as it can be without giving way – so when an ant accidentally steps over the edge of the pit and falls in, the sand beneath it collapses, carrying the ant to the bottom of the pit and into the pincers of the waiting antlion. If the ant tries to scramble up and out of the pit, the antlion tosses a load of sand at the ant, knocking it back down. The antlion then injects venom and digestive fluids into the prey via grooves in its mandibles, and drinks the innards of the ant through these same grooves.
The antlion’s anatomy is as unusual as its method of capturing prey. It has a mouth cavity, but no mouth opening, and no external opening for solid waste. Because digestion takes place outside of its body, the antlion doesn’t accumulate a lot of waste, but what it does accumulate stays inside of it until the antlion matures into an adult. This can be anywhere from one to three years, depending on the species. When fully developed, the antlion constructs a small, round pupal case out of silk and sand, in which it overwinters. It emerges from this case the following spring as a winged adult. (Thanks to Joan Waltermire and John Douglas for photo op.)
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Dragonfly Eclosure: A Vulnerable Time
Dragonfly larvae reside in ponds until the time comes for them to climb up stalks of emergent vegetation or adjacent rocks, split their larval skin and emerge as adults (a process called eclosure). Before it can take flight, a dragonfly has to cling to the substrate long enough to expand its wings by pumping fluid into them, and dry its exoskeleton as well as its wings. During this time the dragonfly is extremely vulnerable – not only can it not fly, but it is usually situated directly above the water. The slightest breeze can blow it from its precarious perch into the water below, where opportunistic predators such as this Eastern Newt are at the ready and make quick work of their helpless prey.
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Common Green Darners Migrating
The Common Green Darner, Anax junius, is one of our largest dragonflies, measuring three inches long, with a four-inch wingspread. It is strikingly colored, with a green thorax and a bright blue (male) or reddish (female) abdomen. As if that weren’t enough to set this dragonfly apart, it is also migratory. Common Green Darners migrate south from August to November, stopping over (like migrating birds) occasionally along the way, resuming flight after resting and refueling. Thanks to radio telemetry, we now know that over a two-month migration, Common Green Darners, each weighing about one gram, can migrate over 400 miles. (Photograph is of a Common Green Darner perched on Bottle Gentian.)
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Eastern Kingbird Nestling With A Mouthful
If you look very closely you will see that the adult Eastern Kingbird has just stuffed a female Widow Skimmer dragonfly (that it has caught and killed) down the throat of one of its nestlings whose beak is pointed skyward. Eventually, after much hard work, the young kingbird succeeded in swallowing the insect, wings and all. The parents will continue feeding their nestlings for at least three weeks after they have fledged.
Dragonfly Eyes
Dragonflies (and bees) have the largest compound eyes of any insect, each containing up to 30,000 facets, or ommatidia (house flies have 6,000). Each facet points in a slightly different direction and creates its own image, and the dragonfly’s brain compiles these thousands of images into one picture. This eye structure enables dragonflies to be extremely sensitive to motion. Because a dragonfly’s eyes wrap around its head, it can see in all directions at the same time (though its forward-looking vision is the sharpest). When capturing prey, a dragonfly doesn’t chase it – it intercepts it in mid-air, and it’s successful nearly 95% of the time. This hunting technique entails calculating the distance of its prey, the direction it’s moving and the speed that it’s flying – an impressive feat any tennis, baseball or football player would especially appreciate!
(Photo is looking down on the eyes of a Common Green Darner. Three simple eyes, or ocelli, are located in the black section below (above in the photo) its two tan compound eyes. The short, thin black lines are its antennae, which can detect wind direction and speed. The yellow section is part of the upper half of its face, or frons.)
A Great Christmas Present!
If you’re looking for a present for someone that will be used year round, year after year, Naturally Curious may just fit the bill. A relative, a friend, your child’s school teacher – it’s the gift that keeps on giving to both young and old!
One reader wrote, “This is a unique book as far as I know. I have several naturalists’ books covering Vermont and the Northeast, and have seen nothing of this breadth, covered to this depth. So much interesting information about birds, amphibians, mammals, insects, plants. This would be useful to those in the mid-Atlantic, New York, and even wider geographic regions. The author gives a month-by-month look at what’s going on in the natural world, and so much of the information would simply be moved forward or back a month in other regions, but would still be relevant because of the wide overlap of species. Very readable. Couldn’t put it down. I consider myself pretty knowledgeable about the natural world, but there was much that was new to me in this book. I would have loved to have this to use as a text when I was teaching. Suitable for a wide range of ages.”
In a recent email to me a parent wrote, “Naturally Curious is our five year old’s unqualified f-a-v-o-r-I-t-e book. He spends hours regularly returning to it to study it’s vivid pictures and have us read to him about all the different creatures. It is a ‘must have’ for any family with children living in New England…or for anyone that simply shares a love of the outdoors.”
I am a firm believer in fostering a love of nature in young children – the younger the better — but I admit that when I wrote Naturally Curious, I was writing it with adults in mind. It delights me no end to know that children don’t even need a grown-up middleman to enjoy it!
Autumn Meadowhawks Mating
Meadowhawks are the only small red dragonflies seen in New England (most males are red, most females are brown).The latest species of dragonfly flying in the fall in this area is the Autumn Meadowhawk (Sympetrum vicinum), which doesn’t emerge until mid-summer. It seems a bit incongruous to observe these dragonflies not only flying, but mating and laying eggs in late October, but that is exactly when you can expect to see them. Until there have been several hard frosts, these winged masters of the air are able to keep active by basking in the sun and warming their flight muscles. The two pictured Autumn Meadowhawks are copulating in the typical “mating wheel” fashion, with the male grasping the female behind her head while the female places the tip of her abdomen at the spot on his abdomen (the seminal vesicle) where he stores his sperm. The female Autumn Meadowhawk lays her eggs in tandem with the male (his presence prevents other male meadowhawks from replacing his sperm with their own).
Naturally Curious with Mary Holland 
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