Many invertebrates, fireflies included, will "act up" when in a stressed situation. In fireflies specifically, the glow is produced by bioluminescent bacteria whom survive in the insects abdomen, which could also be stressed in the same ways the fireflies are. Make sure that they have plenty of food, water, and air and that you try to replicate their natural environment as close as possible to make them feel comfortable. Many insects are also laying eggs this time of year which could also be stressing them. Just make them happy and they should start glowing again!

Maybe they are just flies. Not fire flies.

You have to light them on fire.

Thats how they become fire flies.

I captured myself a mason jar full of fire flies in a reminiscing moment, and they aren't lighting up anymore. When I was young I never remember having this problem before. Mine always lit up my bedroom from my jar. There Is a very dim light in my room but its mostly dark. Help me out please ! I want too see my fireflies <3