Once a year, hordes of flying ants invade Britain – and this year was no exception.
The insects swept the southern part of the country early Wednesday morning in swarms so large they could be seen from space, according to the U.K. Met Office, which is the country's national weather service.
The flying ant invasion was picked up by a weather radar that mistook them for rain.
"These ants are a particular size and they are probably hovering at a certain height in the atmosphere towards the base of a cloud, and the sheer number of them would suggest there's enough for the radar systems to pick up," said BBC Weather presenter and meteorologist Simon King.
King told the BBC that it was the biggest swarm of insects he had seen in the United Kingdom and was a more common sight in parts of the United States.
If you said flying ants 🐜 you were correct! ✔️
We know this to be insect clutter (flying ants) based on inspection of raw reflectivity (Zdr and RhoHV) #WednesdayWisdom #FlyingAnts pic.twitter.com/8HejoLB9u5
— Met Office (@metoffice) July 17, 2019
Twitter users captured the phenomenon and the influx of seagulls that came with it.
The huge number of flying ants is a yearly occurrence known as Flying Ant Day.
Flying Ant Day, however, isn't a specific day: A study by the Royal Society of Biology found that flying ants descend on the U.K. on 96% of days between the start of June and the start of September.
The flying ants are not a different species of ant, but the queens and males of the common black garden ant.
The vast majority of these insects pick the same moment to head out from their colonies because they tend to mate when weather conditions permit.
A cacophony of gulls hoovering up the flying ants over BRISTOL. pic.twitter.com/DrknaIISqs
— Mary Colwell (@curlewcalls) July 15, 2019
Storm: Flying ants invade Wimbledon
This is not the first time the visitors have made headlines.
In July 2017, hundreds of flying ants invaded various courts at Wimbeldon, bugging tennis players who tried to combat the infestation while swatting at tennis balls.
While the annual attack may be inconvenient, the spectacle is essential for maintaining essential ecological processes.
The insects' activity "allows for more oxygen and water to reach the roots of plants and they can even improve soil fertility and help control pests," per the RSB.
Follow Elinor Aspegren on Twitter: @elinoraspegren.
This article originally appeared on USA TODAY: Flying ant swarm in Britain so large it can be seen from space