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Insect Migration

Common Green Darners Appearing

6-20-17 common green darner 021The 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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Monarch Butterflies Reach Wintering Grounds

Two days ago, on November 6th, the first Monarch Butterflies arrived in their 73-mile-wide overwintering area in the Transvolcanic Mountains of Central Mexico. This miraculous flight, which takes a Monarch roughly two months, can be up to 3,000 miles long. Using the sun, and most likely the earth’s magnetic field, they head for specific stands of Oyamel Fir trees, where they will cluster and be protected, unless weather conditions are severe, from extreme temperatures, predators , rain and snow until next March, when their journey north begins. (These butterflies only get about half way back to New England, at which time they mate and lay eggs. The third or fourth generation of these monarchs will reach their eastern destination.) To track the migration of these remarkable insects, go to http://www.learner.org/jnorth/monarch/index.html.
11-8-13 monarch butterfly IMG_6361

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Common Green Darners Migrating

9-16-13 common green darner 249The 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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