萤火虫用英语是：firefly。

firefly 英[ˈfaɪəflaɪ] 美[ˈfaɪərflaɪ]

n. 萤火虫;

[例句]A firefly is a type of beetle.

萤火虫是一种甲虫。

In joy and sorrow, I will be my own firefly.

在喜悦和哀痛，我将是我自己的萤火虫。

A sympathetic firefly would have been enough for me.

如果有一只萤火虫同情地陪伴我，我就知足了。

This is actually the first time I have seen a firefly, so to me it felt amazing.

这实际上是***前次看到萤火虫，所以觉得非常特别。

If you have ever seen a firefly then you have witnessed the same process in action.

如果你曾见过萤火虫，那么你其实就已经目睹了同样的运作原理。