Four-Spotted Chaser

• There is a form called praenubila with greatly exaggerated wing spots, which appears to depend on water temperature during the larval stage and is commoner in Europe than in America.
• It is the official state insect of Alaska.
• The males are markedly territorial: they post themselves on tall plants to watch the whole sheet of water and return to the same perch after every patrol.
• It stars in spectacular, poorly explained mass migrations. Swarms of millions of individuals have been documented crossing Europe, one of them in 1862 in Germany described as a cloud that took hours to pass.
• Those irruptions seem to be triggered by larval overcrowding and by parasites, and have been documented since the 18th century.
• It is identified without difficulty: four dark spots, one at the node of each wing, which give it its name.
• It is aggressive and territorial despite its moderate size, and males defend perches over the water from which they dart out to intercept rivals.
• It is one of the few dragonflies that breeds well in acidic bog waters, which gives it a niche of its own.

Skeleton type

Invertebrate - chitin exoskeleton (insect)

Habitat & environment

Ponds, lagoons, peat bogs and slow-flowing rivers throughout the Holarctic. In Europe it reaches the Arctic Circle, and in mountain areas up to 1,000 m; it is more abundant the further north one goes

Gestation / incubation

The larvae have a two-year development cycle

Sources consulted: IUCN Red List (e.T165469A65834060); Asturnatura; Iberian Odonata (UCM); Wikipedia (Four-spotted chaser)

Best time: From April to early September, peaking in June and July