To prepare where you will keep the fireflies when caught, choose a large jar with a matching lid or enough cheesecloth to cover the top. If you want to use a lid, poke at least six holes in the lid with the screwdriver. Be careful not to make the holes too big; you do not want the fireflies escaping from the jar. If you choose to use cheesecloth, have a rubberband ready to secure the cloth to the opening of the jar. Make sure the jar is clean and dry.
Watch for fireflies to light up once it is dark outside. Fireflies are only active when it is warmer, making summer the best time to look for fireflies. To catch only females, look to the ground or near shrubbery. Females will not move around as often as their male counterparts and will remain close to the ground.
Cup your hands around the firefly, gently. Be sure not to crush any part of the firefly with your hands.
Place the firefly in the jar and quickly cover the opening with cloth or a lid.