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Tuesday, July 10, 2018
This blog post is written by Extension Educator Kelly Allsup,firstname.lastname@example.org
They are the stuff of nightmares, but can make us stand in awe at their beauty. Their dark, extended bodies are poised to attack while lurking under water. They propel themselves through the water with a forceful expulsion of water through their rectum, directing themselves at any unsuspecting insect, small fish, or tadpole. They snatch at their prey with an enlarged lower jaw that looks like it may detach due to the vigor of the attack. Some crawl with long legs while on the hunt and some wait in ambush. When they are fully-grown nymphs, they surface from the water and an adult emerges from the splitting exoskeleton.
If you have not guessed by now, this mystery creature is a dragonfly.
"Dragonflies have been on Earth since before the dinosaurs, and they continue to captivate us today. As adults, their hefty size, vibrant color patterns and spectacular aerial agilities make them a standout in the garden," says Kelly Allsup, University of Illinois Extension educator.
Adult dragonflies are different from their cousins, the damselflies, in that they hold their intricate wings horizontal to their body when perched. Damselflies close their wings when they are perched and have much more slender bodies than the dragonfly. Dragonflies have very large compound eyes that bulge on the sides of their head, allowing for a 360-degree field of vision. Each eye can contain 10,000 to 30,000 individual facets or light-sensing units, allowing for excellent vision.
They will eat flies, mosquitoes, wasps, butterflies, and even other dragonflies, often in dramatic fashion.
"Dragonfly adults, however gorgeous, scoop their prey up with their legs during flight and swiftly tear it to pieces with their massive jaws and razor sharp mandibles, making them the top of the insect food chain," Allsup says. "However, all of this happens too fast for us to see. When flying, they can top out at 30 mph, making it very hard for a 4-Her to catch one for their fair project without the swift and steady sweep of a net."
Any onlooker who visits a pond or lake in the summer has most likely seen the mating ritual of the dragonfly. The sexually mature males are territorial, as water is crucial to complete their life cycle. They make trips to scout for other invading males and mates.
"When a mate is found, the male clutches the females head and she brings her abdomen up to a special structure that holds the sperm. This is known as the wheel position. In some cases, males have adapted special techniques to remove the sperm of a previous mate," Allsup says.
Once they have mated, the females will dart around a body of water looking for a suitable site with submerged vegetation to lay her eggs. All the while, the male will either hover above her or remain clasped to her to prevent other males from mating with her.
Dragonflies are excellent beneficial insects in the garden but require ponds, plant variety, hiding and perching spots in rocks, shrubs and trees, and full sun.