Walker Nature Center
A LOOK INSIDE • Calendar of Events 4 • Kids’ Corner 6 • Get Nuts for Clean Water 7
BRANCHING OUT
Nature Notes
Migrating Dragons
SEPTEMBER
For many, the word migration conjures images of migrating geese in magnificent V’s flying southward in autumn, bound for exotic locales with more abundant food sources. While many bird species migrate, they are not the only groups of animals that fly south from Northern Virginia. Monarch butterfly migration is also well-known. Several other butterfly species also migrate, including Red Admiral and Painted Lady. Lesser known, and lesser understood, is the migration of dragonflies.
By Sharon Gurtz
• Goldenrods bloom. • Hummingbirds migrate to Central America. • Fall colors appear on Sumac and Black Gum trees. • Northern Water Snake and Copperhead young are born.
OCTOBER
• Mushrooms are plentiful. • Deciduous leaves are at peak fall color. • Black-throated Blue and other warblers are migrating. • Asters, Brown-eyed Susans and Goldenrods are blooming.
NOVEMBER
• Deer rut peaks. • Native Witchhazel blooms. • Migratory waterfowl begin to appear. • White-throated Sparrows and Dark-eyed Juncos arrive from the north.
By Ken Rosenthal
Of the 326 species of dragonflies in North America, only 16 are considered regular migrants. Of our local dragonfly species, Common Green Darner, Black Saddlebags, Wandering Glider and Spot-winged Glider are migratory. Migration adds another layer to the already interesting life cycle of these aerial predators.
Growing Up Dragon
Dragonflies begin life underwater, hatching from eggs into aquatic naiads (the immature form of dragonflies). They are fierce predators feeding on aquatic insects, fish and even tadpoles.
Dragonflies undergo incomplete metamorphosis. Naiads grow larger with each molt until a final molt into adulthood. Before the final molt the naiad crawls out of water, typically perching on a rock or vegetation, then shedding its exoskeleton one final time. The new adult dragonfly rests while its wings unfurl and its exoskeleton hardens. Adult dragonflies are amazing aerial predators. Their compound eyes, each composed of 28,000 ommatidia (simple eyes) provide a mosaic view, a very efficient method of motion detection. Dragonflies have two pairs of wings. They can move each wing pair independently of the other or, if needed, each wing independently. This trait allows them an impressive amount of maneuverability, which they use to catch their prey. In flight, dragonflies can reach speeds of 30 miles per hour, make swift right-angle turns, and stop suddenly to hover. Any flying insect is fair game, and larger dragonflies will even consume smaller dragonflies.
Fall 14 Volume Sixteen