×

Editorial: Migration of the dragonflies


Wednesday, August 23, 2017

It’s a sight rarer than an eclipse or the Northern Lights. On the dunes just above the sea, just south of New Hampshire, squadron after squadron of dragonflies passed overhead, all moving south on a northerly wind.

The river of dragonflies flowed by until dusk, thousands, perhaps tens of thousands of the iridescent aerialists. At first we thought that a hatch of small insects must be happening on a marsh in that direction, but there were too many dragonflies for it to be just a feeding spree. It was, we learned, a dragonfly migration.

The migrations will begin any day now if they haven’t started already. The ancient insects follow the same migration paths as songbirds, but their movements are harder to predict. Migrations over land are extremely difficult to encounter. Even along the seashore, which dragonflies like to skirt on their journey, it’s mostly a matter of luck, or informed luck.

New Hampshire is home to or visited by about 165 dragonfly species, according to a remarkable four-year survey conducted by the Audubon Society of New Hampshire, the state’s Fish and Game Department and volunteers.

Only six of those species migrate, but that’s enough to put on a show if someone is lucky enough to see it. To watch dragonflies is to view a marvel of nature.

The insects are 300 million years old and some that flew above the dinosaurs had wingspans that topped two feet.

Dragonflies, though they’ve been vilified throughout history and called things like devil’s darning needle and ear cutter, neither bite people nor sting. But collectively they do eat tons of mosquitoes and other insects. They live but a year.

The migrators mate when they reach their destination. Females lay eggs that hatch into nymphs the size of crickets. The nymphs live on insects, worms, and even tadpoles and small fish, and molt as they grow. When ready to transform into a dragonfly, a nymph climbs a reed, splits its exoskeleton, dries its wings and flies off leaving behind a husk.

Non-migrating adults mate, die in the fall and their nymphs winter underwater to emerge as dragonflies in spring. They are yet another reason to protect and preserve wetlands, rivers, streams, lakes and ponds.

Dragonflies can fly up, down, backward, forward and sideways, turn on a dime and achieve speeds up to 30 mph. Their order, Odonata, includes damselflies. Dragonflies have bigger eyes than damselflies, thicker bodies and broader wings that they spread when at rest. Damselflies, as their name would imply, are thin with wings that narrow at their base. They fold their wings and hold them upright when at rest.

A friend, while standing in the Merrimack River this summer, had a brilliant blue damselfly land on her nose and go eyeball to eyeball. They are harmless.

There are now field guides to dragonflies, as there have long been for birds and butterflies. Fish and Game’s website contains a checklist of New Hampshire species and people are compiling life lists of sightings. Some of their names are almost as beautiful as the things themselves: River Jewelwing, Emerald Spreadwing, Lilypad Forktail, Scarlet Bluet, Powdered Dancer, Riffle Snaketail, Ebony Boghaunter, Eastern Pondhawk, Blue Dancer and our favorite, the Shadow Darner.

We knew something had to hold those shadows together.