A royal invasion — Ecosystems in the Sky

Cyprus today: a royal invasions of thousands and thousands of vagrant emperors (Hemianax ephippiger)!

Recorded by PhD student Will Hakwes and colleagues from University of Exeter.

The vagrant emperor is a monsoon migrant, with a core distribution in the Middle East and Africa. It is a very strong flyer, and have been reported out at sea in the Indian Ocean, all the way across the Atlantic in the Dutch Lesser Antilles and is the only species of dragonfly ever found on Iceland.

In the Atlas Mountains in north Africa, it is also known to engage in vertical migration, or altitudinal migration. This is a type of refuge movement evolved as an adaptation in some species of dragonfly in order to cope with their breeding habitat being periodically unsuitable. In north Africa, the summer months can be very hot and dry, and the ephemeral pools of water the vagrant emperors prefer to breed in may dry out entirely. Thus, immature emperors that have just newly emerged in early spring/ summer may fly up to the cooler mountains, where they will spend the summer months. They reach maturity in late autumn, when the rains return to the lowlands, and then they descend from the mountains to breed or to spend the winter there, delaying reproduction until the next spring.

In years where conditions have been good in the tropical core distribution area, mass emergence of vagrant emperors can occur, and large swarms can move northwards, reaching Europe. This happens quite frequently: 1995 was a mass swarm year, and so was 2016. 2019 appears to be a new one.