Dragonflies In Droves: Is it Migration?

Dragonflies. They’re seemingly everywhere this season.

Patch readers over the past week have said they’ve seen squadrons of them at the beach, bevies of them in their backyards and everywhere in between this summer.

So what gives?

Well, no one really seems to know for certain.

“Dragonfly tracking is really just in its infancy,’’ said Pat Sutton, a naturalist and dragonfly expert in Cape May County.

Some species of the dragonfly — or its cousin, the damselfly — are migratory, while others are not. Some are heartier species, others more sensitive to change, so without knowing exactly which are being seen, it’s difficult to give a concrete answer, naturalists say.

This is the time of year for many species of dragonfly to hatch and take flight. The mild winter that the state experienced could translate into an abundance of the insects that survived the winter, according to Dorothy Smullen, a naturalist at the NJ Audubon Society.

But it could also be a migration of certain species of dragonfly into New Jersey, since much of the country is in drought, said Pete Bacinski, director of the "All Things Birds'' program at the NJ Audubon Society.

----------------------------------------------------------------------------------------------
DRAGONFLY FACT: Dragonflies generally depend on water — lakes, ponds, rivers, streams ditches, marshes and bogs — for survival. Their larvae live underwater from six months to seven years before emerging as an adult dragonfly.

Learn how to attract dragonflies to your back yard with a quick tutorial from the National Wildlife Foundation.
---------------------------------------------------------------------------------------------

One likely answer is that people along the Atlantic seaboard could be seeing the annual migration of two particular species: Spot-winged Glider and the Swamp Darner, according to Mike Crewe, program director of the Cape May Bird Observatory.

"They push north this time of year every year,'' Crewe said. "Some years you might not notice them, but they push up in good numbers if they've had a good breeding year.''

New Jersey is home to some 180 species of dragonfly, according to Wild New Jersey, a nature website. The airborne carnivores eat mainly other insects and can devour its own weight in about a half hour.

"They're quite good insects to have around, because mainly they're feeding on mosquitos,'' Crewe said.

The state Department of Environmental Protection in February added 26 species of dragonfly to its "Species of Special Concern,'' list. The designation identifies species that warrant special attention because they're inherently vulnerable to environmental deterioration or habitat modification, according to the DEP.

There are 54 species of dragonflies in Monmouth County, according to the New Jersey Odonata Survey, a database that tracks the species of dragonflies in the state. Some of those are migratory species, Sutton said.

Of those, dragonfly watchers have noticed that vast numbers of a certain species of dragonfly, occasionally in the thousands, will move ahead of a storm, such as the one experienced in the Shore area Wednesday.

In Cape May on Tuesday, Sutton heard a report of upwards of 90 dragonflies a minute flying ahead of the storm.

“The reports you’re hearing are legitimate,’’ Sutton said. “It’s probably the migration of certain species that people are witnessing.’’

Black saddlebags, a species of dragonfly so named because of the black markings on their wings, are a migratory species found in Monmouth County. So too is the Common Green Darner. Both are known to move in en masse and in large numbers, Sutton said.

In Ocean County and farther south, the Common Green Darner is another migratory species frequently seen in groups, Sutton said.

Where most dragonflies go when they migrate, however, is anyone’s guess at this point. The science is too new to gauge, Sutton said.

“No one knows truly where they’re going,’’ Sutton said. “We’re still working on a way to track them.’’  

In the case of the Swamp Darner or the Spot-winged Glider, Crewe said their migration pattern is quite predictable -- beginning in the Caribbean and flying north sometimes as far as Canada.

"They spread right up the Atlantic,'' Crewe said. "And they survive by having so many.''       

Have you seen an abundance of dragonflies this season? Tell us in the comments.