Emerald damselflies like to perch among reeds, their colour providing good camouflage.

Their habit of perching with their wings half open is characteristic of the family Lestidae and gives rise to their other common name of spreadwings.

L. sponsa mate in the usual dragonfly manner and will form tandem pairs away from water.

The number of stadia is not fixed and in good conditions the last or final larval stage, called F-0 can be reached in as little as 5 weeks.

Furthermore, it was experimentally shown that faster larval growth in time constrained larvae is accompanied by higher activity and feeding efficiency, including cannibalism.

Adults are not sexually mature when they emerge and need a week or more, depending on conditions, before they can breed.

This would disrupt the normal cycle as larva hatched in autumn would not survive the winter.

Mature males have a powder blue colour on the prothorax and on segments 1–2 and 9–10 of the abdomen.

Immature males also lack the blue pruinescence and have greeny brown eyes.

The emerald damselfly has a large Palaeartic distribution, and is found in a band across central Europe and Asia from Spain to the Pacific.