Migratory dragonfly species return to CT


Green menders – large dragonflies, all gorgeous iridescent greens and blues – head to the coast in the fall.

Throughout the state, they congregate in the thousands along Long Island Sound. They will follow the coastline to warmer climes – like birds, butterflies and pensioners, they migrate south. They will cover some 900 miles before reaching their destination.

“You don’t see them in a swarm,” said Valinn Ranelli, seasonal research assistant for the Department of Energy and Environmental Protection’s wildlife diversity program. “It’s like seeing them fly in a line – another and another and another.”

“You see them one, then two, then three,” said David Wagner, a professor of ecology and environmental biology at the University of Connecticut at Storrs.

It is one of the great seasonal migrations in North America. But it is also somewhat misunderstood and unstudied.

“Unfortunately, it doesn’t get much press attention,” Ranelli said. “It’s not that romantic.”

It may be an image problem.

Butterflies flit from flower to flower. Dragonflies zoom. Butterflies are gentle pollinators. Dragonflies are predators, concentrating on their prey and taking it in flight.

“These are big, big, powerful bugs,” said Gale Ridge, an entomologist at the Connecticut Agricultural Experiment Station in New Haven.

“They will eat any insect smaller than themselves,” Ranelli said. “They are very vicious.”

Connecticut has 158 identified species of dragonflies and their cousins, the damselflies. They’re not really flies, they belong to a separate order, Odonata.

It is an ancient species that lived before the dinosaurs. During the Carboniferous Period, more than 300 million years ago, giant dragonflies with a wingspan of two feet buzzed across the vast swamps of this world.

Today’s version are amazing flyers. They have four wings that operate independently. They can fly forwards, backwards, hover, and make 90-degree turns without bulging eyes blinking.

“They can fly 40 miles per hour,” Ridge said.

Although they can perch on tall blades of grass, they cannot walk, Ridge said.

Each dragonfly has six legs. Rather than being designed for trolling, these legs have evolved into barbed baskets that allow dragonflies to grab their prey and quickly hold it.

They have eyes with 30,000 lenses that can see almost 360 degrees.

“There’s a little space underneath that they can’t see,” Ridge said. “If you want to catch one, you catch them from below.”

They need good vision. They cannot hear, do not vocalize, and at best have a rudimentary sense of smell.

Almost all species of dragonflies and damselflies in the state are resident, hunting, breeding, laying their eggs and dying here, with the next generation living as nymphs in ponds until they rise again to themselves. glorify in the summer sun.

But there are five species in the state that migrate, Ranelli said: green rappers, black saddlebags, Carolina saddlebags, spot-winged gliders and wandering gliders.

The latter are the world’s greatest migratory insects, traveling 4,000 miles between Africa and India. By comparison, monarch butterflies travel about 2,400 miles.

UConn’s Wagner said migrating dragonflies can save time by flying high in the atmosphere and catching prevailing winds.

“They can travel at 75 mph,” Wagner said.

These migrations are difficult for scientists to study – even large insects like dragonflies are harder to track than butterflies or birds. New initiatives to study them include the Migratory Dragonfly Partnership, a joint effort of academic researchers and citizen scientists in Canada, the United States and Mexico.

A recent study of green darners – by researchers from the Smithsonian Conservation Biology Institute, the University of Maryland and the Vermont Center for Ecostudies – used citizen science observations and chemical analysis of water molecules in the wings of the green darners.

He found that their migration involves three generations.

In the spring, newly hatched green rappers in the southern United States fly north. They arrive here in April and May – at the beginning of the dragonfly year – mate and lay eggs in the plants along the ponds, then die.

In the fall, the summer-hatched green menders reverse the pattern – they head south, mate, lay eggs, and perish south. Research shows that there is also a third generation in the south that bridges the gap between fall arrivals and spring departures.

Migration patterns show that green darres follow the same migration routes as migratory birds.

And like monarch butterflies, each generation is born with the innate knowledge of when to migrate and where to go.

“It’s in the genes,” said UConn’s Wagner. “A lot of what we do is genetics. Just look at your parents.”

Contact Robert Miller at earthmattersrgm@gmail.com


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