英语听力：自然百科 萤火虫为何会发光？

This week on Why? Tell Me Why! We are answering a viewer question as to why lightning bugs light up.

Lightning bugs light up basically to find a mate. It’s a way that lightning bugs communicate with each other, to call each other together, because someone’s looking for a mate. They have these features in the abdomen of the body: they light up and they can control when they light up, when they blink and how long they blink. And they use that blinking signal to attract each other.

Do both males and females have the lights?

They both have the lights, but the females have brighter lights and bigger lights because they are the ones who are trying to attract males to them. Each different species of lightning bug has a different pattern of flashing to only attract its own species. In this way, if there are five different species of lightning bugs all in the same field, they can tell who is their same species and who is not. So, they know who to be attracted to. There is an enzyme in these insects called luciferase. And it uses something that insects make from the food they eat to bind together and generate light with very little heat. So, one of the interesting things about fireflies is they generate this light without making heat.

The only time we see lightning bugs lighting up is when they are on a quest to find a mate? That’s a, that’s one time they'll use their lights?

There is one other time when lightning bugs will use their lights and that is there is one species of lightning bugs that uses the light to attract other lightning bugs which she will aim to eat.