Odonata is an order of predatory flying insects that includes the dragonflies and damselflies. The two groups are distinguished with dragonflies usually being bulkier with large compound eyes together and wings spread up or out at rest, while damselflies are usually more slender with eyes placed apart and wings folded together along body at rest. Adult odonates can land, but rarely walk.
A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of dragonflies are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threatens dragonfly populations around the world. Adult dragonflies are characterized by a pair of large, multifaceted, compound eyes, two pairs of strong, transparent wings, sometimes with coloured patches, and an elongated body. Many dragonflies have brilliant iridescent or metallic colours produced by structural coloration, making them conspicuous in flight. An adult dragonfly's compound eyes have nearly 24,000 ommatidia each.
Damselflies are flying insects of the suborder Zygoptera in the order Odonata. They are similar to dragonflies but are smaller and have slimmer bodies. Most species fold the wings along the body when at rest, unlike dragonflies which hold the wings flat and away from the body. Damselflies have existed since the Jurassic, and are found on every continent except Antarctica.
Aeshna isoceles is a small hawker dragonfly that is found in Europe, mostly around the Mediterranean, and the lowlands of North Africa. Its common name in English is green-eyed hawker. In Britain it is a rare and local species and is known as the Norfolk hawker. It has a brown colour with green eyes and clear wings and also a yellow triangular mark on the second abdominal segment which gave rise to its scientific name. It used to be in the genus Anaciaeschna as it has several differences from the other members of the genus Aeshna. Its specific name is often spelt isosceles.
The petaltails of the family Petaluridae are among the most ancient of the extant true dragonflies, having fossil members from as early as the Jurassic, over 150 million years ago.
A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which distinguish brightness and color. The image perceived by this arthropod eye is a combination of inputs from the numerous ommatidia, which are oriented to point in slightly different directions. Compared with single-aperture eyes, compound eyes have poor image resolution; however, they possess a very large view angle and the ability to detect fast movement and, in some cases, the polarization of light. Because a compound eye is made up of a collection of ommatidia, each with its own lens, light will enter each ommatidium instead of using a single entrance point. The individual light receptors behind each lens are then turned on and off due to a series of changes in the light intensity during movement or when an object is moving, creating a flicker-effect known as the flicker frequency, which is the rate at which the ommatidia are turned on and off– this facilitates faster reaction to movement; honey bees respond in 0.01s compared with 0.05s for humans.
The Cessna A-37 Dragonfly, or Super Tweet, is a light attack aircraft designed and produced by the American aircraft manufacturer Cessna.
Bromo-DragonFLY is a substance related to the phenethylamine family. It acts as a potent full agonist for the 5-HT2A receptor.
The brown hawker is a large dragonfly about 73 millimetres (2.9 in) long. It is a distinctive species and is easily recognised, even in flight, by its brown body and bronze wings. At rest, blue spots on the second and third segments of the male's abdomen can be noticed; these are absent in female.
The southern hawker or blue hawker is a species of hawker dragonfly.
Erythemis simplicicollis, the eastern pondhawk, also known as the common pondhawk, is a dragonfly of the family Libellulidae, native to the eastern two-thirds of the United States and southern Ontario and Quebec, Canada. It is a dragonfly of ponds and still waters. The species is distinguished in that the female is bright green with a banded abdomen and the mature male has a blue abdomen with a green face and green and blue thorax.
The scarlet dragonfly is a species of dragonfly in the family Libellulidae. Its common names include broad scarlet, common scarlet-darter, and scarlet darter.
Somatochlora, or the striped emeralds, is a genus of dragonflies in the family Corduliidae with 42 described species found across the Northern Hemisphere.
Petalura gigantea, the giant dragonfly or south-eastern petaltail, is a species of dragonfly in the family Petaluridae from southeastern Australia. Males have body length of 6–7.5 cm (2.4–3.0 in) and a wingspan up to 11 cm (4.3 in), while females have body length of 8–9 cm (3.1–3.5 in) and a wingspan up to 12.5 cm (4.9 in). This makes it a very large species of dragonfly, although it is exceeded by a few other species, including the closely related northeast Australian giant petaltail.
The eastern amberwing is a species of dragonfly in the family Libellulidae. It is very small, reaching a total length of no more than 25 millimetres (0.98 in). The males have orange or amber wings. Both sexes have a red pterostigma.
Chalcolestes viridis, formerly Lestes viridis, is a damselfly of the family Lestidae. It has a metallic green body and at rest it holds its wings away from its body. Its common name is the willow emerald damselfly, the green emerald damselfly, or the western willow spreadwing. It has an elongated abdomen and pale brown spots on its wings and resides in areas of still water with overhanging trees.
Telephlebiidae is a family of dragonflies endemic to eastern and south-western Australia. They are medium-sized to very large dragonflies, generally found around streams.
Dragonfly is a planned spacecraft and NASA mission to send a robotic rotorcraft to the surface of Titan, the largest moon of Saturn. It is planned to be launched in July 2028. It would be the first aircraft on Titan and is intended to make the first powered and fully controlled atmospheric flight on any moon, with the intention of studying prebiotic chemistry and extraterrestrial habitability. It would then use its vertical takeoffs and landings (VTOL) capability to move between exploration sites.
The Dragonfly project was an Internet search engine prototype created by Google that was designed to be compatible with China's state censorship provisions. The public learned of Dragonfly's existence in August 2018, when The Intercept leaked an internal memo written by a Google employee about the project. In December 2018, Dragonfly was reported to have "effectively been shut down" after a clash with members of the privacy team within Google. However, according to employees, work on Dragonfly was still continuing as of March 2019, with some 100 people still allocated to it.
