How to Feed Fireflies. Catching fireflies is a fun summer activity for children, who may enjoy holding the insects in their hands and keeping them in a jar to watch them glow through the night. While fireflies are harmless and can be kept in captivity, it is best for the firefly to be released after a few days. In the meantime, concerned children may want to offer food to a pet firefly.
Keep captive fireflies in a jar or container that has a screen top or plenty of holes to admit fresh air. Without fresh air to breath, a firefly will not be able to survive even one night.
Place a shallow dish or bottle cap in the jar with a small amount of drinking water. Make sure that the water is shallow to ensure that the firefly does not fall in to the dish and drown.
Mix together some warm water with a high concentration of fine sugar and place it in another shallow dish or cap. Fireflies feed primarily on nectar and sugar water is the best substitute for natural nectar.
Provide fireflies with small slugs, mealworms or other small insects if desired. Fireflies prey on smaller, soft-bodied insects, but do not eat meat frequently, so a firefly may or may not choose to eat insects that are offered.
When keeping fireflies, ensure that children and pets do not eat the fireflies. The chemicals that produce fireflies' light are toxic to reptiles and mammals. If offering other insects to captive fireflies, do not offer large insects, spiders or other insects with pincers that may harm the firefly.