The Western Willow Spread-wing (Chalcolestes viridis), also known as the Willow Emerald Damselfly, is a large, metallic-green damselfly found across Europe and North Africa. Famous for its tree-dwelling habits, it uniquely lays its eggs in the bark of overhanging branches rather than underwater.
Key Physical Facts
Size: Relatively large and long for a spreadwing, with a typical body length of 39 mm to 48 mm and a wingspan of up to 59 mm.
Coloration: Both sexes are a striking, dark metallic green with no blue "dusting" (pruinosity).
Wing Spots: They feature pale, creamy-brown wing spots (pterostigmata) outlined in dark veins.
Identifying Mark: They have a distinct, small green marking shaped like a thorn on the side of the thorax.
Behavior & Habitat
The "Spread-wing" Stance: Unlike most damselflies that fold their wings parallel to their body while at rest, spread-wings hold their wings at a distinct 45° angle.
Tree Preference: Adults spend a significant amount of time in marginal shrubs and trees (such as willow and alder), often quite far from water.
Flight Period: They are active late in the season, primarily from August to October.
Life Cycle & Reproduction
Egg Laying: Unlike most damselflies, females lay eggs inside incisions in the bark of live, overhanging branches. The process leaves distinct oval scars or dimples in the wood.
Overwintering: The eggs develop for a few weeks and then enter a dormant period (diapause). They overwinter safely inside the tree bark.
Larval Stage: In the spring, the eggs hatch, the larvae drop into the water below, and they quickly develop into adults within a couple of months.
