The Lampyridae are a family of elateroid beetles with more than 2,000 described species, many of which are light-emitting. They are soft-bodied beetles commonly called fireflies, lightning bugs, or glowworms for their conspicuous production of light, mainly during twilight, to attract mates. Light production in the Lampyridae is thought to have originated as an honest warning signal that the larvae were distasteful; this was co-opted as a mating signal in the adults. In a further development, female fireflies of the genus Photuris mimic the flash pattern of Photinus species to trap their males as prey.

जुगनू या खद्योत कीटों का एक परिवार है। इनके पंख होते हैं। ये जीवदीप्ति उत्पन्न करके अपने संगी को आकृष्ट करते हैं या दूसरे जानवरों का शिकार करने के लिये इसका उपयोग करते हैं। इनके द्वारा उत्पन्न प्रकाश पीला, हरा, लाल आदि हो सकता है। यह प्रकाश रासायनिक क्रिया द्वारा उत्पन्न किया जाता है। इसमें अवरक्त और पराबैंगनी आवृत्तियाँ नहीं होतीं।