This is a large damselfly with a total length of up to 48 millimetres (1.9 in) and a hindwing length of up to 36 millimetres (1.4 in).The male has translucent wings which each have a broad, dark iridescent blue-black spot (or band) across the outer part. On immature dragonflies the spot is dark brown. The body can be a metallic blue or blue-ish green.
The dark wing patch of the male starts at the nodus (the slight dip midway down the upper edge of the wing) but can reach up to the wing-tip in southern races. In the very similar species C. virgo (Beautiful Demoiselle), the dark starts before the nodus.The female has translucent, pale green iridescent wings with a white patch near the tip (a pseudopterostigma), and a metallic green body.
Females can lay up to 10 eggs per minute for 45 minutes. They lay in a wide variety of emergent or floating plants, sometimes even submerging to do so. The eggs hatch after 14 days. The larvae have very long legs and are stick-shaped. They develop over two years, usually. They tolerate muddy water and overwinter buried in mud. When they are ready to moult into an adult, they climb up a suitable reed or plant and shed their skin.
Text and photographs by Wikipedia