The blood sucking creatures originate in Asia but have gradually been moving west. This is the first time they have been spotted in Sweden.
The so-called vampire butterflies can have a wingspan of up to 45 mm and get their name from their diet of mammal blood which the males suck up through their long snout.
Insect expert Jan-Olov Björklund told TT news agency that people should not be alarmed if they come across a vampire. They normally eat fruit and plants, he says, blood is more of a delicacy to them.