This is a lovely vintage Glass Wasp Trap, which is very likely to be hand blown about a century ago. The glass is quite thick with imperfections and bubbles through it. There is a narrow gauge wire loop wrapped around its neck for hanging in a tree. There are three wasp shaped impressions on the outside of the glass. The trap sits on three small glass feet, one of which is chipped at the base but the trap still sits firmly and balanced on a flat surface.
To use the trap pour sweet liquid such as a mixture of honey and water or sugar and water into the well which runs around the inside of the base. Place a cork into the open neck to prevent the flies and wasps from escaping. The insect is attracted to the sweet liquid, and as it tries to get out, it will fall into the liquid and drown.
These kinds of vintage hanging glass traps are said to be more effective at trapping the wasp than other methods. If it stops the fruit fly wasp from eating my citrus fruit then I am willing to believe this.