The arrival of dragonflies heralds the arrival of summer, whether they are delicately perched on a cattail or floating over a pond. Found on every continent except Antarctica, these gigantic four-winged, horizontal insects are easily identified by their large bodies, hovering movements, and zipping movements. Dragonflies can fly forward at speeds of up to 35 mph and backwards just as gracefully taking off vertically like a helicopter. Each nearly touching compound has approximately 28,000 individual eyes, called ommatidia.
In addition to being ancient, dragonflies are among nature’s most useful insects. They do not represent dragons, despite what their name might lead you to believe.
A rocky start
The life cycle of a dragonfly begins in the water. During midsummer, females float over freshwater areas and submerge their bellies, laying eggs that hatch in about 7 to 8 days. These larvae, also known as naiads or nymphs, hunt aquatic species, mosquitoes, or tiny fish using lower jaws that stretch and expand laterally, drawing food into their jaws. They can stay in the water for up to 3 years. They might even consume other dragonfly nymphs as food.
The nymphs move forward quickly, spitting out the water they have sucked into their stomachs. It takes them between six and fifteen molts, or about 12 hours, to develop into full-fledged adult dragonflies. Hunting for flies, mosquitoes and midges is all that adults do for almost a month. They can catch food in flight due to the upward tilt of their arms, which resembles a basket.
Adults also look for opportunities to find a partner. The autoinsemination process begins when the male bends his body to move the sperm from the main genitalia, located at the end of his belly, to the complementary genitalia, located immediately below the sternum.
When he spots a woman open to approaching him, he grabs her by the back of the head with physical restraints at the end of her belly, and the two walk off.
As they settle in, the female forms a “mating wheel” that can actually take on the appearance of a heart by bending her belly down to touch her secondary genitalia. (They occasionally mate in the sky.) After a brief mating period, the female may lay her eggs.
In addition to predators (especially mosquitoes), dragonflies also serve as food for fish and birds, which is crucial for their environment. Scientists believe that these insects are accurate bioindicators of the health of an ecosystem, since they depend on fresh water and constant levels of oxygen.
According to the first comprehensive study of insect species, ten percent of dragonfly species were threatened with extinction in 2009. The creatures are endangered due to pollution, non-native flora, and the degradation of freshwater ecosystems. , particularly ponds, swamps and wetlands.
For example, a professionally imported tree called Australian black locust displaces yellow Presba, a dragonfly found exclusively in South Africa. The rapidly spreading invasive plant blocks the sunlight that grasses need to thrive. This dragonfly is currently listed as endangered by the World Conservation Union.