Flying insects are often a nuisance. Mosquito bites leave itchy red marks, while bees and wasps sting if they feel threatened.

However, there's something magical about dragonflies; their appearance and behavior are not annoying.

Dragonflies belong to the order Odonata and the family Anisoptera. The dragonfly has well-developed wings, and the base of the hind wings is slightly larger than the base of the forewings. When resting, their four wings are spread out flat on both sides.

The head is flexible and the antennae are short. The compound eyes are well developed, with 3 single eyes, and the chewing mouthparts are powerful. The abdomen is thin, and the legs are long, thin, and weak with hooked spines; larvae are short and thick, with rectal gills and no tail gills. Dragonflies are a typical insect with incomplete metamorphosis and the insect with the most eyes.

Dragonflies are an ancient insect that can be traced back to 320 million years ago.

Taxonomically, the dragonfly order is divided into three categories: the extinct ancient Odonata, the original Odonata, and the modern Odonata.

From a time point of view, the three are in a sequential evolutionary relationship: the ancient Odonata only survived in the early Late Carboniferous; the Proto-Odonata appeared in the late Paleozoic and became extinct at the end of the Triassic; the Odonata appeared in the Permian and Jurassic. Radiation occurred and descendants continue to this day.

Ancient dragonflies were much bigger than we imagined. They appeared around 300 million years ago. During the Mesozoic Era, dragonflies gradually grew in size and became the "overlord" of the sky at that time. As a predatory animal, their main food is various insects and some small vertebrates, such as juvenile lizards, and they are out-and-out carnivores.

So, how big were the "overlords" in the air at that time?

While words can be speculative, fossils provide proof. According to Zheng Daran, a researcher at the Nanjing Institute of Paleontology, Chinese Academy of Sciences and a doctoral candidate at the University of Hong Kong, a team led by Zhang Haichun discovered a 200-million-year-old primitive dragonfly fossil on the northwest edge of the Junggar Basin.

This newly discovered primitive dragonfly has a single wing length of 101 to 102 mm and a wingspan of 210 mm, approximately the length of the short side of an A4 paper.

The same team led by Zhang Haichun also discovered a nearly completely preserved dragonfly forewing fossil in the Jurassic Daohugou fossil layer in Ningcheng, Inner Mongolia, a few years ago. The single wing is 107.6 mm long and 14.3 mm wide. Based on this, it is inferred that the dragonfly's wingspan is 225 mm, it is the fourth largest dragonfly in the world.

Furthermore, the Permian giant-veined dragonfly found in the United States from the Early Permian had a wingspan of up to 710 mm.

Why did the ancestor of the dragonfly look so tough? Scientists have long speculated that changes in oxygen levels in the atmosphere may have played a key role in their rise and fall.

A new study from the University of Arizona shows that raising dragonflies in a hyperoxic environment (oxygen above average) can make their bodies grow larger. Although they failed to breed a dragonfly with a wingspan of nearly 1 meter, increasing the size of the dragonfly by 15% is already a very interesting discovery.