14/06/2025
Yesterday late afternoon, Friday 13th June 2025, in Olhão, Algarve, Portugal, no one could avoid noticing the swarm of thousands (maybe millions) of dragonflies flying around the city. In some locations, the presence of the insect clouds was so intense that we could spot their shade on the ground.
It was the migration of the Vagrant Emperor (Anax ephippiger) dragonfly.
Never seen before by local inhabitants.
For those who carefully watched the city's nesting Swifts as they caught dragonflies in flight and deposited them into their chicks' mouths with surprising regularity, it was a memorable and amazing wildlife show.
And for the swifts, and the other insectivorous birds, it was a totally unexpected and wonderful funtastic banquet.
Over evening and all night, the migration carried on, with insects flying towards the North. It was very easy to spot them crossing the road N125, all in the same direction.
The next day (Saturday) morning, although it was easy to detect a few insects around the town, the quantity had no comparison with the day before
Let me tell you about it. The story begins in tropical Africa. There, during the monsoon season, the Vagrant Emperor breeds in sunny, shallow ponds and marshes created by heavy rains. The female lays her eggs by inserting them into plant stems, rotting vegetation, or mud. The larva, which feeds on aquatic insects, develops in 2 to 3 months—a very rapid development for a dragonfly, allowing it to colonise temporary environments.
As soon as they emerge, between September and November, the new generation of adults begins to migrate. Depending on the wind direction, they then reproduce in the rest of Africa, the Arabian Peninsula, India and sometimes in southern Europe. The third generation emerges at the end of winter and will migrate again. Driven by warm southerly winds, thousands of Vagrant Emperor can then be observed in Europe in spring. The migration abilities of this species are exceptional, and it has even been reported in Iceland, Guyana, the Caribbean and Japan! The Vagrant Emperor is therefore a migratory dragonfly that reaches our territories via favourable winds. At the beginning of the dragonfly observation season (March-May), the individuals observed have migrated from their African birthplace. On the other hand, the individuals observed in September or October could have been born in Europe. However, this species cannot survive the winter in Europe, and the latest generation of dragonflies will likely return south, although this has never been formally demonstrated.
