A while back, we spotted a very convincing mechanical butterfly in a jar in a store. Really, you have to see it; it's uncanny.
This firefly-in-a-jar version must be by the same folks. The illusion isn't quite as startling, probably because it is limited to a single firefly. Still, the effect is good -- especially at night. They show the firefly simulacrum at night later in the video below.
There your have it: a little bit of summer preserved in a jar for those urban/winter nights. No fireflies were harmed in the making of this film. I can live with the diminution of 3 AAA batteries (included).
Here is where you can check out the electronic firefly in a jar