Swarms of Flying Ants Overtaking Great Britain Show Up as Rain on Radar

Every summer, flying queen ants descend upon Great Britain en masse, swarming in search of suitable mates, shedding their wings upon making a match and settling down in new colonies. Their mates, meanwhile, die within days of the nuptial flight—per London’s Natural History Museum, male black garden ants’ “sole reason for existence is to mate with … queens.”

Earlier this week, a group of particularly prolific winged ants took flight in southern England, forming swarms so dense that they showed up as rain on radar. According to BBC weather presenter Simon King, who highlighted the eerie incident in a Wednesday Twitter post, meteorologists noted the disparity because they “knew it was dry in the south of England, and yet the radar was showing this very light precipitation.”

Speaking with BBC News, King adds, “You can tell it's not rainfall because it has that eerie look to it. … 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.”

Although black garden ants, or Lasius niger, grace the skies of Great Britain nearly every day between June and September, the seasonal phenomenon is widely viewed as a singular occurrence. Colloquially dubbed Flying Ant Day, the purportedly one-day event actually unfolds over several weeks throughout the summer. As Adam Hart, a University of Gloucestershire entomologist who co-authored a 2017 study debunking the popular perception, writes for BBC News, publicly reported data reveals that flying ants “are much less coordinated across space and much less synchronized” than most believe.

Hart notes, “You might have flying ants in your garden one day and your neighbour might have them the week, or even the month, after.”

In an interview with the Guardian’s Aaron Walawalkar, the entomologist further states that the timing of the ants’ flight depends on weather conditions across the U.K. Typically, the insects embark on their annual mating ritual when hot, humid weather follows rain.

According to Lisa Hendry of the U.K.'s National History Museum, smaller winged males known as drones and larger winged queens depart the nest in order to form new colonies. As Walawalkar explains, the queen emits pheromones upon taking flight, encouraging the drones to follow and compete for the honor of mating with her. Ultimately, several of the strongest males emerge victorious, while the rest fall prey to predators such as birds.

Once a queen ant successfully mates, she chews off her wings, returns to the ground and begins the business of launching a colony. The sperm exchanged during this initial encounter is enough to fertilize the queen’s eggs for the rest of her lifetime (up to 15 years in the wild and 28 in captivity), ensuring the colony’s growth and longevity. Once a colony reaches its maximum capacity, new queens embark on their own nuptial flights and start the cycle all over again.

Despite their semi-apocalyptic appearance and behavior, black garden ants pose no threat to humans. (Wimbledon aside, of course: As tennis player Caroline Wozniacki commented at last year’s tournament, “They’re in my mouth and in my hair and everywhere—we need to do something. Is there a spray? I want to be here to focus on tennis, not eating bugs.”)

In fact, Hendry writes, the insects’ tunneling activities play a key role in improving soil quality, and their annual swarming trips provide a steady source of food for many bird species. Seagulls, however, may want to refrain from snacking on the winged ants. Hart tells the Guardian that the birds can appear drunk after eating just a few of the insects, perhaps as a result of the formic acid found in the ants’ bodies.

Speaking with Walawalkar, Hart says this week’s satellite sighting was probably the result of increasingly advanced technology, not a sudden jump in ant population.

“If it is increasing, I think it is a potentially a good thing,” he concludes. “But I would be cautious to interpret that.”

Meilan Solly | | READ MORE

Meilan Solly is Smithsonian magazine's associate digital editor, history.