A firefly met a spider at dusk once, and they exchanged a few words in the secret language of arthropods, a patois of gestures and pheromones that no larger creature could ever hope to understand.
“I have often wondered why it is you glow,” said the spider. She was busy spinning a fresh web for the wave of prey that would arrive with the dusk. “Surely it only attracts those who would eat you.”
“We find our mates that way,” replied the firefly, alighted on a nearby branch, with caution. “They shine in the dark and so do we.”
“But I find my mate without such blinking,” replied the spider. “He comes for my scent and my web, and does not speak or display anything but the utmost obedience as he dances, lest he be my next meal. None need know what passes between us.”
“Ah, but surely one of the big ones has seen the dew on your web in the morning sun,” the firefly said. “As great a light as mine, or greater, and worse because you cannot move it.”
“But I can move myself,” the spider sniffed. “And the big ones do not often seek me for their repast, as they know my fangs drip with venom. You have no such fangs.”
“My children do.” The firefly flitted its wings casually. “They eat the slimy garden-creepers below before turning to the sweet flower-juice in their old age.”
“But we are not speaking of your little worm-brood, but of you. What is to keep me from eating you now? I can leap farther than you can fly, and faster, and my sight is far beyond your little shining orbs.” Thus saying, she jumped.
The firefly had predicted this; what had seemed a mere idle twitch had really been the warm-up to his takeoff. “There is one thing you should know,” he said as he flew away. “Our lights are also a warning to your kind. A firefly is toxic to any who would eat it, as surely as your venom is. Remember that, and your manners, the next time you meet one.”