Firefly Luciferin: A benzothaizole which is oxidized by LUCIFERASES, FIREFLY to cause emission of light (LUMINESCENCE).Luciferases, Firefly: Luciferases from FIREFLIES, usually Photinus, that oxidizes FIREFLY LUCIFERIN to cause emission of PHOTONS.Luminescence: Emission of LIGHT when ELECTRONS return to the electronic ground state from an excited state and lose the energy as PHOTONS. It is sometimes called cool light in contrast to INCANDESCENCE. LUMINESCENT MEASUREMENTS take advantage of this type of light emitted from LUMINESCENT AGENTS.Beetles: INSECTS of the order Coleoptera, containing over 350,000 species in 150 families. They possess hard bodies and their mouthparts are adapted for chewing.Luminescent Agents: Compound such as LUMINESCENT PROTEINS that cause or emit light (PHYSICAL LUMINESCENCE).Fireflies: The family Lampyidae, which are bioluminescent BEETLES. They contain FIREFLY LUCIFERIN and LUCIFERASES. Oxidation of firefly luciferin results in luminescence.Luminescent Measurements: Techniques used for determining the values of photometric parameters of light resulting from LUMINESCENCE.Luciferases: Enzymes that oxidize certain LUMINESCENT AGENTS to emit light (PHYSICAL LUMINESCENCE). The luciferases from different organisms have evolved differently so have different structures and substrates.Cnidaria: A phylum of radially symmetrical invertebrates characterized by possession of stinging cells called nematocysts. It includes the classes ANTHOZOA; CUBOZOA; HYDROZOA, and SCYPHOZOA. Members carry CNIDARIAN VENOMS.Dodecanol: A saturated 12-carbon fatty alcohol obtained from coconut oil fatty acids. It has a floral odor and is used in detergents, lubricating oils, and pharmaceuticals. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)Benzothiazoles: Compounds with a benzene ring fused to a thiazole ring.