Title text: I feel bad for Earth 2 and their shadowflies.
Transcript: xkcd comics picture
[Cueball and Megan are seen in silhouette (drawn in white against a black background) throughout the strip. They are walking to the right.]
Cueball: So where is this spot?
Megan: It's just up ahead.
[Cueball and Megan continue walking.]
Megan: You know,
Megan: fireflies didn't have to exist.
[Closeup on Megan.]
Megan: The ocean has lots of bioluminescence, but it's less common on land.
Megan: Creatures that glow are pretty rare here.
[Cueball and Megan continue walking. The light of one firefly is seen to their right.]
Megan: So it's not some niche whose exploitation was inevitable.
Megan: If insects hadn't stumbled on their fatty acid enzyme trick, Earth just wouldn't have fireflies.
Megan: Ooh, look!
Megan: They're starting!
[A panel as wide as the first four combined. Cueball and Megan stand in the tall grass, at night, and many stars can be seen in the sky above them. Above and below them, to their left and right, the lights of dozens of fireflies can be seen.]
Cueball: I'm glad we got a planet that has these.
Megan: Yeah, it's a good one.
This reminds me of the song by Owl City. Owl City - Fireflies