`Vampire watermelons are a folk legend from the Balkans, in southeastern Europe. The story is associated with the Roma people of the region, who originated much of vampire folklore among other unusual legends.
The belief in vampire watermelons is similar to the belief that any inanimate object left outside during the night of a full moon will become a vampire. According to tradition, virtually any kind of melon or pumpkin kept more than ten days or after Christmas will become a vampire, rolling around on the ground and growling to pester the living. People have little fear of the vampire melons because of the creatures’ lack of teeth. One of the main indications that a melon is about to undergo a vampiric transformation (or has just completed one) is said to be the appearance of a drop of blood on its skin.’