Dragonflies (infraorder Anisoptera) are flying insects commonly found near freshwater habitats. Due to their carnivorous or insectivorous nature, dragonflies are highly agile flying predators. Possessing four membraned wings with knotted veins attached directly to their muscles, dragonflies can fly in every direction—forwards, backward, and upside-down. They can 0also move each of their four wings independently, allowing them to hover and swivel in place. They have huge compound eyes that allow some species to have a field vision of nearly 360 degrees. Dragonflies are also known by other names such as darner, devil’s darning needle, or devil’s arrow.
The largest dragonfly in the world is Petalura ingentissima, or the giant petaltail. A giant petaltail has a wingspan of 160mm or 6.2 inches.
The Giant Petaltail – Largest Dragonfly in the World
Petalura ingentissima, or the giant petaltail is said to be the world’s largest dragonfly. The giant petaltail is endemic to Queensland, Australia. Its scientific name stems from the Latin adjective ingens, meaning “huge.” The species belongs to the genus Petalura, native to southwestern and eastern Australia.
It is described as a large heavily-built dragonfly with some yellow markings on its black body and clear wings. The males have a black petaltail and the females have an orange petaltail. The females can grow up to 125mm (body length) with a wingspan of 158-162 mm.
The larvae of the giant petaltail, called “pit dwellers”, are distinct in the way they hunt passing prey while living in burrows along the river margin. Larval dragonflies are largely aquatic, and the semi-aquatic nature of the petaltail larvae sets them apart. Giant petaltails, even as adults, choose wet areas such as swamps as their habitat.
The diet of a giant petaltail consists of anything small enough for them to catch, including mosquitoes, flying ants, mayflies, damselflies, butterflies, termites, and other dragonflies.
The Genus Petalura
Petalura is a genus that houses very large dragonflies in the family Petaluridae. Five known species belong to this genus and are endemic to Australia.
The second largest dragonfly in southeastern Australia, Petalura gigantea, also belongs to the genus Petalura.
Is the Giant Petaltail the largest dragonfly in the world?
Over the years, debate has been on which dragonfly is the largest. The two primary contenders for this spot are the Petalura ingentissima (giant petaltail) and Anax walsinghami (giant darner). The giant darner has a wingspan of 5 inches and a body length of 5 inches.
The giant petaltail, when overall dimensions are considered, is the largest dragonfly in the world. The members of genus Tetracanthagyna can have longer wings. The species Cholorogomphus papilio possess wings with a larger surface area.
The Giant Darner
The giant darner (Anax walsinghami) is the largest dragonfly in the United States. The giant darner has a long black body with large blue metallic spots covering it making the dragonfly easy to spot. The giant darner can sometimes be confused with a common green darner. Besides its bright coloration, the giant darner’s most distinguishable feature is its size and abdomen. Its abdomen makes up for more than two-thirds of its body. The green head and the thorax make up less than one-third of its body. Like most dragonflies, the giant darner has transparent wings but with black intricate veins woven throughout.
Giant darners prefer to inhabit wet and boggy areas such as ponds, streams, and marshes. Their diet consists of anything they can catch while flying, including smaller insects like mosquitoes. Like typical dragonflies, their larvae are aquatic (naiads or nymphs).
The giant Hawaiian darner (Anax strenuus), also known as pinao, is also considered one of the largest living dragonflies, with a wingspan of 152 mm. The genus Anax belongs to the family Aeshnidae. These dragonflies are endemic to the Hawaiian Islands and are most commonly found at higher altitudes.
The Largest “Dragonfly” to Ever Exist
The largest insect to ever exist is related to the modern-day Odonata (the order that dragonflies and damselflies are members of). They belong to the extinct genus Meganeura. The giant extinct dragonfly, Meganeura monyi, had a wingspan of 71 cm (28 in). While these iconic giant insects had bodies that could be compared to that of crows, they weighed very little, measuring up to only 1 lb.
The species of the genus are said to have dwelled in open habitats near the edge of bodies of water and humid wetlands. Their fossils were first discovered near Coventry in France in 1880. The Meganuera inhabited the planet during the late Palaeozoic period, roughly 300 million years ago. They were carnivores with large appendages, which they presumably used to catch their prey, dubbing their behavior as “hawk-like” and similar to “perchers.” Meganeura means “large veins,” the genus originating from the intricately veined wings their species possessed.
The Meganeura was at the top of the food chain. A lack of flying predators allowed the species to evolve to grow as large as they did. The Meganeura belongs to the superorder Odonaptera, many details of odonate biology have been borrowed to study the fossils effectively.
The anatomical details of their heads, including their bulging eyes and mouthparts, are unknown due to some species’ poor preservation. A few fossils could be retained that have helped envisage the torso and head. The Meganura were found to have sturdy jaws with sharp teeth owing to their predatory nature.
These enormous flying insects’ extinction has been hypothesized to have occurred due to declining oxygen levels. There has been research that has proven the connection between the size of an insect and atmospheric oxygen levels. Basically, oxygen is diffused through its tracheal respiratory system in such a manner that puts an upper limit on its body size. 300 million years ago, the atmosphere’s oxygen level was much higher than it is now. The declining levels of oxygen eventually brought about the end of the Meganeura.
While today’s dragonflies and damselflies cannot grow as large as their prehistoric relatives, they are still a sight to behold. Dragonflies are harmless and feast on what humans would consider pests. For this reason, many people even want to lure dragonflies to their backyards or gardens. They are remarkable predators who are extraordinarily nimble in their movements. Whether or not these insects live to grow larger in the following centuries, their evolution would no doubt be fascinating.