it is called a guépière which I think is a much nicer word than wasp trap. Filled with water and rotting fruit they will attract wasps which fly in from underneath. They then find themselves unable to leave and drown in the food they came for. Highly effective and highly recommended if you have lots of wasps. In recent years made by many glass makers, including Empoli, India, Romania and various French glass works. In France you sometimes see the very old ones, going right back to the 18th century.