Orange-spotted emerald  (Oxygastra curtisii)

Classified as Near Threatened (NT) on the IUCN Red List (1), listed on Appendix II of the EU Habitats Directive (4) and listed on Appendix II of the Bern Convention on the Conservation of European Wildlife and Natural Habitats (5).

As a typical emerald (Corduliidae spp.), this medium-sized dragonfly possesses vivid emerald green eyes and a metallic green body, with a dark, bronzed tinge to the long abdomen (2) (3) (6) (7). The presence of conspicuous deep yellow spots on the upper surface of the abdomen, which merge almost into a longitudinal stripe, is a characteristic feature of this species and earns it its common name (7). Unlike males, the wings of females are suffused with yellow along their leading edge, a feature that helps distinguish between the sexes (2) (6).

In Europe, the orange-spotted emerald is mainly found in Spain, Portugal and France, but also occurs in Belgium, Luxembourg, Germany, Switzerland and Italy, and has become regionally extinct in the UK and the Netherlands (1). Three records also originate from Morocco, North Africa (2) (8).

Found in and around slow-moving, tree-lined rivers with muddy or sandy bottoms (7) (9).

Mature orange-spotted emerald males establish territories at favourable breeding sites along a stretch of water, 10 to 20 metres in length, which they patrol continuously, flying back and forth low above the water and banks. Females venturing towards the river are quickly coupled with a male, and mating continues in the heights of the surrounding trees. Females then return to the river to lay their eggs in calm, shaded areas, unaccompanied by the male (9). Males change their territory rather frequently. This reproductive period in which adults are ‘on the wing’ lasts until early August (2) (3) (10).

The eggs hatch two to ten weeks after deposition and the larval period extend over two or three years. The larvae are mostly confined to leaf litter and detritus, accumulated between tree-roots along river banks, where they hunt. The larvae metamorphose into the adult form and emerge as dragonflies mainly in May or June, dependent on the climate. After emergence, the adults undergo a pre-reproductive phase away from the river known as the maturation period, which probably lasts around ten days (7), when they normally develop their full adult colour (11). After this period, they will return to the river to establish their territory.

Adults may feed at any time, but hunt particularly in the evening, when they attack swarms of midges above the river. The night is generally spent in the foliage of surrounding trees (7).

Although the orange-spotted emerald is not currently considered threatened, extensive water pollution, irrigation, large-scale stream alterations, global warming and associated summer droughts and stream drying may pose significant future threats, and an overall decrease in population sizes is therefore anticipated. Fortunately, the highest population densities that exist in south-west France and north-western Iberia are less likely to suffer than elsewhere, due to the mountainous nature of the area and therefore lower levels of agricultural pressure, river pollution and alteration, and drought (1).

While there are no conservation measures currently targeting this species, there is a need for control of water pollution, conservation of ‘natural’ stream and river structures, and preservation of tree borders (1).

View information on this species at the UNEP World Conservation Monitoring Centre.