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The Keeled Skimmer (Orthetrum coerulescens) is a captivating species of dragonfly belonging to the family Libellulidae. This medium-sized dragonfly presents a unique combination of physical and behavioral traits that distinguish it from other members of its family. Found across a wide range of habitats in Europe and Asia, from the United Kingdom in the west to Japan in the east, the Keeled Skimmer thrives in various environments, including heathlands, bogs, and the edges of forests near slow-flowing rivers or lakes.

One of the most striking features of the Keeled Skimmer is its appearance. Adult males exhibit a distinctive powdery blue body with a characteristic black line running down the center of the thorax and abdomen, which gives the species its common name. The abdomen is slightly flattened, which is more pronounced in males, giving them a keeled appearance. Their wings are clear, with a span that can reach up to 60mm, and feature a dark pterostigma (the colored, often thickened cell located at the leading edge of each wing). In contrast, females and immature males are more of a yellow-brown color, with similar but less pronounced body markings. Both sexes have large, compound eyes that are typically brownish in color, which provide them with excellent vision for detecting prey and avoiding predators.

Behaviorally, the Keeled Skimmer is known for its territorial nature, especially among males during the breeding season. They often perch on exposed vegetation or stones, vigilantly scanning their surroundings for intruders or potential mates. When a rival male encroaches upon their territory, a high-speed chase ensues until the intruder is driven away. The mating process involves a unique aerial display, where the male clasps the female behind the head with claspers at the end of his abdomen, and the pair performs a tandem flight before the female lays her eggs in water.

The larval stage of the Keeled Skimmer is aquatic and can last for up to three years. During this time, the larvae undergo several molts, gradually increasing in size until they are ready to emerge as adults. This transformation usually takes place early in the morning, with the newly emerged adult resting nearby to allow its wings and body to harden.

The Keeled Skimmer is a diurnal predator, both in its larval and adult stages. As larvae, they are ambush predators, feeding on a variety of aquatic invertebrates. Adults feed on flying insects, which they catch on the wing using their speed and agility. Their diet includes mosquitoes, flies, and other small insects, making them beneficial for controlling pest populations.

Despite their widespread distribution, the Keeled Skimmer faces threats from habitat destruction and pollution, which have led to declines in certain areas. Conservation efforts are focused on preserving their natural habitats and ensuring clean water sources to support their complex life cycle. Observing a Keeled Skimmer in its natural environment can be a rewarding experience for nature enthusiasts, offering a glimpse into the fascinating world of dragonflies and their role in the ecosystem.