Where Migrants and Residents Come Together
 

Migratory dragonflies have been moving north for several weeks in North America, mating and laying eggs as they go. And, with the arrival of sustained warmer weather, resident dragonflies that overwintered as nymphs in ponds, wetlands, or streams are also beginning to emerge as adults.

 

Dragonfly and damselfly nymphs develop into adults across months to years, depending on species, shedding their skin (molting) numerous times as they grow. Nymphs of some species survive winter by entering a resting state called diapause. As water and air temperatures increase and days lengthen in the spring, overwintering nymphs become active again, and can complete their metamorphosis and emerge as adults. The final-stage nymphs develop directly into the adult form, with no intermediate pupa stage. Because this type of development is less advanced in evolutionary terms than the larva-pupa-adult metamorphosis seen in butterflies, bees, beetles, and caddisflies, dragonfly metamorphosis is called "simple" or "incomplete". But anyone who has ever watched a winged adult dragonfly burst forth from the final instar nymph will agree that the process is anything but "simple".

Emergence sequence of a dragonfly. Left to right, splits the nymphal skin; emerges and leaves behind an exuvia; unfurls wings and expands body; the teneral allows cuticle to harden before taking flight.

 

As dragonfly and damselfly nymphs go through successive molts, small wing pads develop on the thorax. These become larger as the nymph matures, but give little indication of the size and beauty of the adult wings that will eventually break free. As adult emergence nears, the nymph stops feeding, shifts to aerial breathing, and crawls from the water to find a firm substrate on which to emerge. Some species climb up on aquatic vegetation to emerge, while others may crawl long distances from the water, even climbing onto tree trunks. The events that follow are spectacular. The new adult expands its thorax until the nymphal skin splits, allowing it to pull its head, legs, and thorax free. It then hangs backwards for a time to allow the body to harden and strengthen, at which point it reaches forward, holds on to the substrate, and pulls its abdomen free. The crumpled wings expand as body fluids are pumped through the network of veins; this fluid is then withdrawn and pumped into the body to lengthen the abdomen. Emerging adults are very vulnerable and subject to multiple threats such as being picked off by birds as tender morsels to feed nestlings.

 

Newly-emerged adults, called tenerals, have a distinctive shine on their recently unfurled wings, weak flight, and pale coloration, which can make them appear very different from mature adults. Tenerals seek refuge away from water, where they feed, develop their definitive color patterns, and become sexually mature. When a teneral makes its first flight it leaves behind it's the cast-off skin of the final-stage nymph, called an exuvia.

 

The presence of exuviae is evidence that a species is successfully breeding there. Reporting exuviae and first-of-the-year sightings of migratory species at your Pond Watch site helps us examine the timing of migration and differences in arrival of migrants vs. emergence of residents, and gives insights into the local life history of resident and migrant populations of the same species. The timing of your observations is key! Migratory and resident populations of Common Green Darner (Anax junius) can inhabit the same pond or wetland. Migratory adults emerge in the north in late summer and fly south; spring migrants return north to mate and lay eggs before overwintering resident nymphs have completed development to adults. Resident adults emerge in late spring and summer, laying eggs that hatch into nymphs that will spend the winter in diapause. This year, mature adult Common Green Darners were reported in February and March from California and southern Oregon and April saw a surge of migrant sightings in the southeast and northeast, while May 12 provided a surprisingly early report of a teneral Common Green Darner in southeast Massachusetts. Reports such as these give important clues about the phenology of migrants versus residents in different regions of North America.

 

So as the days grow longer and warmer and dragonfly development continues, explore the vegetation around your local pond for tenerals or the exuviae they left behind. If you're lucky, you might even get to witness an emergence! 

This newly released publication provides guidelines for landowners to help them create, manage, and maintain backyard ponds to attract dragonflies and damselflies. Download your copy here! 

  
ADULT EMERGENCE
Check out videos on dragonfly emergence and see the whole process in time lapse; from the nymph as it crawls out of the water, to the teneral adult, with pale coloration and shiny wings taking its first flight.
Please share photos and stories of the wildlife that visit your backyard pond. Email your stories, photos of dragonflies and other wildlife, or photos of your pond. We'll include as many photos or stories as we can in future annual reports & e-newsletters.
 
  

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The Migratory Dragonfly Partnership is composed of dragonfly experts, nongovernmental programs, academic institutions, and federal agencies from the U.S., Mexico, and Canada. Together, we are combining research, citizen science, and education and outreach to better understand North America's migrating dragonflies and promote conservation of their wetland habitat. 

To learn more about our work, visit www.migratorydragonflypartnership.org.
Photo Credits: Banner: A newly emerged teneral Twelve-spotted Skimmer (Libellula pulchella), by Peg Serani; 
 Side bar: Cover photo of Backyard Pond Guidelines, by Walter Chadwick, citizen science volunteer; 
Backyard habitat, by Celeste Mazzacano; 
In text: A sequence of dragonfly emergence, by Peg Serani

Migratory Dragonfly  I  Partnership 628 NE Broadway, Suite 200  I  Portland, OR 97232 USA
www.MigratoryDragonflyPartnership.org

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