The find was made in a light trap for moths, set by a butterfly watcher on the south coast of Skåne.
It's a dream species that I've wanted to find ever since I started collecting butterflies, Jonas Waldeck says to Sydsvenskan.
The oak processionary moth, as the species is actually called, has caused a lot of commotion in Denmark in recent months because it is dangerous to humans.
The moth caterpillar can cause an allergic reaction with rashes and breathing difficulties. Danish schools, among others, have closed for decontamination to get rid of it.
Didrik Vanhoenacker, biologist on duty at the Swedish Museum of Natural History, emphasizes that isolated finds have been made in Skåne before. A single butterfly is not a sign that it has established itself in Skåne.
A single male won't produce any babies, he tells TT.
But the proximity to Danish Amager, where it has established itself, means there is reason to be careful, he thinks.
The name comes from the insect's behavior of walking in close ranks in procession once they have eaten all the leaves on an oak tree, after which they move on to the next one.
"The caterpillar from hell" is a dramatic nickname - perhaps a little overly dramatic, Vanhoenacker thinks.
"So, annoying hairs in all glory, but we're not talking about shrapnel. Somewhere you have to sit still in the boat and be aware that there are places in the world where it's hell," he says.
Corrected: In a previous version there was an incorrect statement about the find.
