What about the dragonfly's life span?
Soon after mating, impregnated females deposit fertilized eggs by dipping their abdomens into shallow water alongside vegetation, or into soft muck. The eggs undergo a maturation over winter and hatch into larvae the next spring. The ugly larvae have been called little "dirt balls" since dirt clings to the hairs that cover their bodies. They are voracious aquatic predators feeding night and day (the larva at the left was cleaned up for the photograph by Lauren Pintor). They capture their food by means of a hinged lower lip that can be flipped forward to trap prey on stiff bristles. The lip can be extended about a third of the length of the larva's body, giving them enough reach to even capture small fish. Larvae breathe by means of gills inside the anal chamber, into which water is pumped, then forcibly expelled.
Over a 3-4 year period, larvae molt many times as they grow their way toward adulthood and an aerial existence. When they reach a pre-adult stage, they stop feeding and crawl out of the water onto vegetation, where they gulp air to inflate and expand their bodies. They break out of their larval skin and next inflate their wings, which become outstretched. Thereafter they wait as their body parts dry. Then they take flight to feed on other flying insects some distance from their watery birthplace.
The adults live for only 4-7 weeks. After vigorous daylight feeding on mosquitoes, deerflies, flying ants, and whatever they can capture in flight, females return to water after copulating to lay their eggs. Males join them and patrol the swale or pond where eggs are being deposited. It is a short, but intense, adulthood of feeding, sexual interaction, and egg deposition.
Some interesting facts about dragonflies in general
1. Dragonflies are living fossils, having remained unchanged for over 300 million years. The fossil at the right is from the Pennsylvanian Period and is at least 300 million years old. It has a wingspan of 6 1/2 inches and was obviously a member of the clubtail group. Modern clubtails closely resemble this fossil specimen. The first known dragonfly fossil had a wingspan of about 29 inches.
2. The four wings of dragonflies can move independently of one another and are powered by large muscles that almost fill the thoracic cavity. The wings typical beat about 35 times a second and can propel the dragonfly at speeds up to about 35 miles per hour.
3. In spite of their delicate appearance, the wings are remarkably strong, which is a tribute to the weight/strength characteristics of the tiny tubes, called veins, that reinforce the dragonfly wing. Dragonflies can do everything a helicopter can do, and much more quickly. They hover, fly backward, do loops, barrel rolls, and execute very tight turns. A hovering dragonfly can accelerate to top speed in a fraction of a second.
4. The most highly developed sensory system of a dragonfly is that relating to sight. Their eyes cover a visual area of almost 360 degrees and they are designed to detect even the slightest of movements and light flickering off the wings of prey insects. One scientist suggested that 80% of the dragonfly's brain is dedicated to processing and responding to visual information.
5. Dragonflies may have a fearsome look to some people, but they are harmless to humans. In earlier times they were referred to as "horse stingers" of "devil's darning needles." In fact, many dragonflies are quite beautiful, as in the case of the Calico Pennant (Celithemis elisa), on the left, and the Widow Skimmer (Libellula luctuosa), on the right:
6. Some dragonflies can fly for great distances. For example, swarms of Wandering Gliders (Pantala flavescens) have been spotted over the Atlantic Ocean hundreds of miles from land.
7. Although most temperate dragonflies are active only when ambient temperature is above about 50 degrees F., they have the ability to regulate their internal temperature within a narrow range. Also, by "whirring" (vibrating) their wings for a few moments, they can raise the temperature of their flight muscles enough to fly.
Some other dragonflies of The Ridges Sanctuary
Other members of the Emerald Family seen at the Sanctuary include the Brush-Tipped Emerald (Somatochlora walshii - see photo below), Williamson's Emerald (S. williamsoni), Kennedy's Emerald (S. kennedyi), American Emerald (Cordulia shurtleffi), and the Racket-Tailed Emerald (Dorocordulia libera). Chalk-Fronted Corporals (Ladona julia) and Common Green Darners (Anax junius) are among the earliest appearing species, followed by Skimmers, Emeralds, Canada Darners (Aeshna canadensis), and later, Meadowhawks (Sympetrum sp.) that persist into late fall. Other darners often seen are Lance-Tipped Darners (A. constricta), Shadow Darners (A. umbrosa) and Black-Tipped Darners (A. tuberculifera - see photo below). The Canada Darner is especially abundant. About 30 species of dragonflies occur with some frequency at the Sanctuary. Calico Pennants (Celithemis elisa), Black Saddlebags (Tramea lacerata), Twelve-Spotted Skimmers (Libellua pulchella), and Widow Skimmers (Libellula luctuosa), are commonly seen in the spring. A valuable guide to dragonflies in Wisconsin is: Legler, Karl and Dorothy, with Dave Westover, 1998. "Color Guide To Common Dragonflies Of Wisconsin," published by Karl Legler, 429 Franklin St., Sauk City, WI 53583 (email@example.com).
At the top is a lateral view of a male Black-Tipped Darner, a species recently reported in the Sanctuary. At the bottom is a dorsal view of a male Brush-Tipped Emerald dragonfly; at the right is a lateral view of the "brushy" clasper of the male, shown in close-up.
Just what is The Ridges Sanctuary?
The Ridges Sanctuary is a 1,200 acre nature preserve in Baileys Harbor, WI, along the shoreline of Lake Michigan. It consists of sandy ridges created along ancient shorelines by wind and wave action, combined with incremental dropping of the lake level over a period of about 1,000 years. Today, long water-filled swales lie between the ridges. The shallow swales are spring fed, and the ridges themselves are covered by boreal forest. Several miles of trails wind back and forth along the ridges, and interconnect by bridges over the swales.
The Ridges Sanctuary is noted for its wildflowers, with over 25 species of wild orchids, and as a "dragonfly heaven." The great glacier moving down into Wisconsin from Canada brought diverse species of plants from the far north to Door County. As the glacier receded (about 10,000 years ago) many of them established themselves in and around what is now The Ridges Sanctuary because of the cooling effect of Lake Michigan breezes. The mission of the Sanctuary is to preserve and protect ecologically significant natural areas, and provide environmental education opportunities. It is officially recognized as a National Natural Landmark by the National Park Service. Its website is: <ridgesanctuary.org>.
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