Rajah Brooke's birdwing

The Raja Brooke Butterfly is an uncommon insect that was introduced in City Folk. It is the only butterfly to be attracted to water, rather than plants. It is easier to catch between morning and noon, and harder to catch later on during the day. The "Bugs and Fish window" in City Folk says, "Flashing black wings with bright green markings make it easy to identify."

Donating to the Museum in City Folk
Upon donating to the museum, Blathers the curator will say;

"...I must say, I'm quite impressed with your ability to catch such an impressive butterfly... The Raja Brooke butterfly, I must tell you, is one of the larger tiger butterflies. Naturally, its antennae and proboscis also rank as some of the largest around. Be not proud, vile beast! Your cute red collar and fancy name do not fool Blathers!"

It can be found in the bottom-left enclosure in the insect exhibit, flying around the pond.

Further Information
The butterfly is actually a type of birdwing. It has distinctive black and electric-green markings, which are more prominent in the males, while the females have white markings. Both have a red head and another strip of red afterward, which is called a collar. It was named by Alfred R. Wallace in 1855, after James of Sarawak, the Rajah of Sarawark. It is also called the Rajah Brooke butterfly, sometimes mistaking the Animal Crossing spelling as a mistake - though both are acceptable. They can be found in the rainforests of Borneo and the Malaysian Peninsula, and is featured as the national butterfly of Malaysia. It is registered as being under protection.