Mediterranean crooked flower white Brussels in three years
One of the butterflies that you can still see flying this autumn is the crooked flower white. No one is better placed than butterfly expert Thomas Merckx, professor of ‘global change biology’ at the VUB, to explain how special that is: until three years ago, this relative of the little cabbage white had never set foot in Brussels.
“The skewed white is actually a Mediterranean species,” Merckx explains. “Ten years ago, the most recent site was the Rhone Valley in France. Around 2005, Swiss biologists noticed something strange: it suddenly appeared in rock gardens in cities.”
From purchasing, the crooked flower white rose spectacularly. “The butterfly entered Belgium via the Rhine valley. In 2016, the first copies were spotted in the East Cantons and Bastogne, followed in 2019 in Brussels. By 2021 it was already much more common here. Last summer the brand new migrant was on the Pachecolaan, in the Pentagon. Everyone is amazed at how fast it has gone.”
Heat Island Effect
Changes at work. Merckx: “They are more cold-tolerant, develop faster, and above all: the females are much less picky when it comes to host plants. They no longer only choose the crooked flower to lay their eggs, but also other plants from the same family. Rapeseed from arugula, for example, from large sand cabbage, actually wild arugula.”
Crooked flower whites on the existing species in Belgium are not, says Merckx. “They just brighten up life in the city. In addition to the Atalanta, Peacock-eye and Goldfinch, city dwellers can now also see this newcomer fly into the year, as it has two to three generations in one year. Climate change and the urban heat island effect naturally help with this.”