The taxonomic order, Odonata, is ancient. Its members were here long before dinosaurs roamed the planet, and they survived the mass extinction that turned T. Rex and his buddies into crude oil.
Dragonflies were among the first winged insects to evolve and have developed exceptional flying and hunting skills. Their wingspans range from 2 to 5 inches, though fossilized specimens have been found with wingspans up to 2 feet.
Because a dragonfly can beat each of its four wings either together or separately, it can fly at speeds approaching 20 miles per hour. They can hover, fly straight up and down, fly upside down, or even fly backwards. They are known as being the world’s fastest insect and are superior hunters, capturing their targeted prey nearly 97 percent of time. It’s a remarkable success rate given that other aerial hunters such as falcons and owls only claim a successful hunt 25 percent of the time, and the king of beasts only about 30 percent.
Besides their flying proficiency, dragonflies owe their hunting prowess to their eyesight. The insect’s head is almost all eyes, five to be exact. They have two large compound eyes with 30,000 facets, each with a lens and multiple light-gathering proteins.
Each facet of its compound eyes faces in a different direction unlike its three simple eyes which point forward. Dragonflies can also perceive ultraviolet and polarized light and have an almost 360-degree field of vision.
Dragonflies are carnivores. Mosquitoes, gnats and other six-legged fliers are all targets but most of a dragonfly’s life is not spent flying or hunting above ground. All but about a month or so of its sometimes-multi-year existence is spent underwater.
After hatching from eggs layed near the water’s edge, on aquatic plants or in the water dragonfly nymphs grow. They will outgrow their exoskeletons and molt as many as six to 15 times, depending on species.
Dragonfly nymphs are peerless hunters. Their ability to extend their lower mandible to grab their prey and bring it back into their mouth for chewing is lightning fast and has been compared in National Park Service writing to the “extendable mouth of the titular Alien creature in the classic film series.”
Newly-hatched tadpoles, mosquito larvae, tiny fish and other insect larvae are in peril when dragonfly nymphs, are on the hunt. In addition to their “spring loaded” mandibles, dragonfly nymphs are jet-propelled. They suck water in through a specialized rectal chamber, to wash across gills in their abdomen so they can breathe. Then they rapidly expel the water from the same chamber, propelling themselves forward with a burst of speed, like a jet ski.
After a final molt the nymphs leave the water, breathe air, attach themselves to vegetation and begin metamorphosis. A winged dragonfly emerges from a crack in the attached exuvia (exoskeleton), pumps blood into its new wings and after drying in the sun, goes on the hunt for food and a mate.
Dragonfies can bear brilliant colors in remarkable designs on their bodies and wings. Depending on their species, the insects can be brilliant blue to orange to black with attached “saddlebags.”
Along with their many color schemes, dragonflies have garnered numerous monikers such as mosquito hawk, horse stinger (although they don’t sting) and the devil’s darning needle because of their long needle-like abdomens.
This is the time of year visitors may see a diversity of dragonflies on the refuges of the San Luis NWR Complex.
The Merced National Wildlife Refuge which is located at 7430 West Sandy Mush Road, the San Luis National Wildlife Refuge and the San Joaquin River National Wildlife Refuge comprise the San Luis National Wildlife Refuge Complex. Its headquarters and visitor center are located just north of Los Banos off Highway 165 at 7376 South Wolfsen Road.
The refuges are open to visitors daily from one half-hour before sunrise to one half-hour after sunset. The visitor center is open Monday through Friday except federal holidays from 8 a.m. to 4:30 p.m.
For more information call 209 826-3508 ext. 127.
