A spectacular butterfly migration with no return journey

If you have spent any time outdoors over the past few weeks, chances are you have noticed them. On coastal paths, in valleys, in gardens and even in urban areas, butterflies have been appearing in numbers that feel anything but ordinary. People have been stopping to photograph them, posting about them online, and trying to figure out what is happening.

It is one of the most impressive painted lady butterfly migrations seen over the Maltese islands in recent years.

The painted lady, known scientifically as Vanessa cardui, travels thousands of kilometres between Africa and Europe every year, crossing deserts, open sea and mountain ranges. Malta sits at the centre of the Mediterranean, making it a natural stopping point for butterflies to rest and feed before continuing north.

Naturalist Arnold Sciberras has been watching the phenomenon closely. He says influxes like this tend to occur on a roughly one-to-two-year cycle, but the numbers this season have been exceptional, with painted ladies turning up across the full length and breadth of the islands. Alongside them, in unusually high numbers, has been the small white, Pieris rapae, a less celebrated species that is also capable of long-distance travel. Seeing both together in such volume does not happen every year.

Godwin Degabriele, a trained butterfly farmer and researcher who has spent years studying Malta’s Lepidoptera, says the explanation lies in Africa. As temperatures rise, the vegetation painted ladies depend on to lay their eggs dries up.

“These animals migrate northwards to find a better chance of laying their eggs on fresh, flourishing plants,” Degabriele says.

The same dynamic plays out on every continent with different butterfly species. Degabriele points to the Monarch butterfly crossing the American states. In the Mediterranean, he adds, the African Monarch, passes through Malta too. It cannot breed here as its food plant does not grow locally, and so it continues on, most likely toward Sicily.

One thing Degabriele is keen to correct though is the idea that painted ladies migrate south again in autumn. They do not. Once they arrive at their destination, they mate, lay their eggs and die. There is no return journey.

More butterflies, or more phones?

Before drawing too many conclusions from this year’s numbers, Degabriele offers a caveat. The apparent scale of the migration may not be as clear-cut as it seems.

“I’m not aware of a scientific study that has compared this year with previous years,” he says. “It’s not necessarily that there are more butterflies. It’s just that there are more people reporting it.”

Social media has changed what gets noticed. A migration that might have passed with little comment a decade ago now generates hundreds of posts and photographs within days. But that is not the same as a scientific count.

The species that cannot leave

The painted lady is, by most measures, not a species under threat. It is one of the most widely distributed butterflies on the planet and adaptable enough to be very difficult to threaten. A good migration year is not a conservation story.

The conservation story is about the species that never leave.

Malta has around 22 butterfly species. Only four are migratory. The remaining species are residents with no ability to move elsewhere when conditions deteriorate.

Degabriele says habitat destruction and increasingly dry summers have stripped away the plants these butterflies need to complete their life cycles. When a food plant dries up too early in the season, caterpillars starve before they can develop and surviving adults find nowhere suitable to lay their eggs.

Of the 22 species, around 11 are still seen with regularity. The others have become exceedingly rare.

The thousands of painted ladies currently passing through Malta are a reminder of what migratory insects are capable of. For the species that live here permanently, the picture looks rather different.