Fireflies, lightning bugs, blinkies. Whatever you call them. the ASPCA Animal Poison Control Center warns that Photinus sp. are highly toxic to lizards: It takes half of a firefly to kill a full-grown bearded dragon.
Fireflies or Photinus sp. contain lucibufagins, steroidal pyrones similar to bufodienolides present in Bufo toads (such as the Cane Toad) or cardenolides present in plants, such as Digitalis sp. Death has been reported in bearded dragons and chameleons after ingestion, but other species of lizards are also likely susceptible.
Bearded dragons are thought to be more susceptible to toxicosis as they are fairly indiscriminant eaters. There have been reports of bearded dragons eating a firefly, vomiting the firefly and then reingesting the firefly, despite evidence that it was causing significant nausea.
Once a firefly is ingested, affected lizards will often head shake, orally gape, retch and vomit. This progresses to dyspnea, color change and death.
The onset of signs is typically noted 15 minutes to 2 hours post exposure, and death occurs within 2 hours post exposure. Treatment is theoretical, as to date, there are no reported cases of firefly ingestion in lizards who have survived long enough to receive veterinary care. Treatment would consist of decontamination (gastric lavage, activated charcoal), thermoregulation and oxygen.
Digoxin immune Fab (Digibind®) has been used successful for related compounds, but there are no reports of its use with lucibufagins or in lizards.