Powdered dancer. Wandering globetrotter. Common sand dragon. These are only a few of the exotic creatures encountered by Pam Hunt on her quest last summer.
Hunt, a conservation biologist with New Hampshire Audubon, surveyed the Connecticut River for odonates, the order of insects that includes dragonflies and damselflies. “Odonate” literally means “toothed jaws.” These jaws pursue mosquitoes and other small prey both underwater and in the air.
New Hampshire Audubon biologists track the ebb and flow over time of a wide range of creatures, from lofty birds such as the peregrine falcon to the lowly insects, including the dragonfly. Populations rise and fall due to many factors, including weather and the abundance of prey. Populations may decline over time due to habitat degradation, habitat destruction, and the effects of persistent toxins; in other words, factors that people control.
Here on planet Earth, insect species far outnumber bird species. Over the last decade, conservation organizations like Audubon have begun systematically tracking the distribution and populations of insects such as butterflies and dragonflies, which tend to be more sensitive to environmental changes than their feathered predators. As such, odonates are indicators of habitat condition and sentinels of ecological change. Hunt, who describes herself as a “bio-diva,” particularly enjoys the hunt for odonates.
In New Hampshire and Vermont, there are eight families of odonates represented by nearly 200 species. A local pond might have a half-dozen species active at one time. Among the array, you might notice a group of metallic-colored bluets, which are easily disturbed from perches just above the water. You might also note a large twelve-spot skimmer with chocolate wing spots patrolling a stretch of shoreline. Or find a brilliant ruby meadowfly perched in the sun and moving its head to track a deer fly.
One of the identifying characteristics of all odonates is that all four wings can move independently. With only 30 wing beats per second (slow for insects), odonates can reach surprising speeds - up to 60 miles per hour. Typically the front and hind wings create turbulence in a syncopated rhythm that that allows for dazzling speed and instantaneous turns.
Dragonflies on the wing capture our attention, but the majority of their days are spent underwater. The aquatic, immature “odes” are called naiads or nymphs. The naiads grow incrementally over the course of a year, through a series of molts. At each stage, the naiad sheds its exoskeleton, emerges, swells in size, and then, when its armor hardens again, returns to the pursuit of underwater fare.
Among the cobbles and vegetation on the bottom of the river, the naiads walk, nearly weightless, seeking prey. If frightened, they can squirt water from their abdomen and jet along for short distances through a cloud of silt. This octopus-like trick may help them elude a fish or a probing beak. Upon sighting a mosquito or caddisfly larva, the dragonfly’s jaw unhinges and swings forward to grasp the prey with jagged teeth.
Odonates have a gradual metamorphosis and never undergo a pupal phase. In an early morning of a summer day, a naiad will crawl up a rock or a stem and change from an underwater stalker to a free-flying adult. In this process, the back of the insect splits open lengthwise and the soft new adult emerges from within, bending backward, then forward, to escape its aquatic form, leaving its exuvia, or shed exoskeleton, behind. Like a freshly emerged butterfly, the wings inflate with fluids, then drain and harden. This is the adult and final stage of an odonate’s life.
After emergence, the “tenerals” fly to sunny glades or meadows to feed and mature. The females of many species only return to the water for moments of mating and egg-laying. Otherwise, they forage widely.
Hunt’s survey included a day along the Connecticut River from Sumner’s Falls, south of White River Junction, to the Cornish-Windsor covered bridge. Stopping along the route, Hunt deftly netted perching dragonflies. Other species she sighted on the wing. From her kayak, she methodically canvassed the riverbanks for light brown exuvia clinging to riverside roots, branches, ledges, and snags above the water line. Some of these the biologist recognized in hand. Others would have to wait for identification back at her desk.
Hunt’s most exciting find last summer was a common sand dragon, a chocolate brown dragonfly with triangular yellow marks. Despite its name, the common sand dragon is anything but common in these parts, normally being a more southerly species. This specimen was the first recorded for the entire watershed. The naiads of the sand dragon are relatively intolerant of pollution, so the find was a positive sign along a river that was once known as the nation’s “best-landscaped sewer.”