What makes a firefly's light?

   A firefly's light comes from two juices that it makes in its body. Neither kind of juice will shine all by itself, but when the two mix together with air, they glow. A firefly doesn't burn your hand if you catch it. The light is cool, like the light from a fluorescent bulb.
   Scientists believe that fireflies attract their mates by flashing their lights. But no one can yet explain a strange habit of fireflies in Thailand. Large numbers of them gather in trees. Then suddenly they all light up at the same moment. On and off, on and off — sometimes several trees full of fireflies will flash in unison.
   Another glowing creature is the ferrocarril worm that lives in South America. It has eleven pairs of little green lights along its sides and one red light on its head. If you annoy the worm it turns its lights on.