How and why do lightning bugs glow?

(WHTM) - It is a sure sign of summer when you begin to see those lightning bugs (or fireflies) glow across the land. But have you ever wondered how they glow and why?
North Carolina State University says these insects are not flies or bugs; they are actually soft-winged beetles that really produce light, an ability called bioluminescence. The university says this is relatively rare in living organisms. Where can you get the best tacos in New Mexico?To produce this light, fireflies use special or