Sooty copper fritillary

Only the leading lepidopterists at Ba Sing Se University know how many butterflies there are in the Earth Kingdom, but the sooty copper fritillary species is one of the most coveted. It is often found flying near the dust of copper mines, so following them can be both flighty and prosperous to the wallet. Many wealthy miners have gotten their start by following these creatures.

History
After Haru's capture by the Fire Nation, Katara decided to get herself arrested in order to save him and the other Earthbenders on the prison; while she and Sokka were discussing their plan, Aang was playing with a sooty copper fritillary. The butterfly was in fact near an area known for coal deposits.