Bioluminescence in a firefly A firefly sends out bioluminescent signal. (more) How Do Fireflies Light Up? Ask the Chatbot a Question More Actions Share Share Share to social media Facebook X URL https://www.britannica.com/science/How-Do-Fireflies-Light-Up Feedback Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login). Feedback Type Select a type (Required) Factual Correction Spelling/Grammar Correction Link Correction Additional Information Other Your Feedback Submit Feedback Thank you for your feedback Our editors will review what you’ve submitted and determine whether to revise the article.

　　External Websites Ask the Chatbot a Question Written and fact-checked by The Editors of Encyclopaedia Britannica Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors. The Editors of Encyclopaedia Britannica Last Updated: Apr 4, 2025 • Article History Table of Contents Table of Contents Ask the Chatbot Fireflies light up summer nights using a chemical process known as bioluminescence, the key chemical players of which are the light-emitting compound luciferin and the enzyme luciferase. Luciferin, in the presence of luciferase, undergoes oxidation, resulting in the production of oxyluciferin, an unstable excited-state intermediate compound. As oxyluciferin quickly returns to a lower energy state, it gives off light. Because the reaction generates very little heat, and nearly all the energy is released as light, firefly light is often referred to as “cold light.” In the chemical reaction that produces firefly light, luciferase plays a crucial role as a catalyst, ...(100 of 186 words)

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