Tiger butterfly

The Tiger Butterfly is a common butterfly that can be found near red flowers during the spring and summer months. They travel slowly and so can be caught easily. This butterfly can often be found on or around red or pink flowers. The "Tiger Butterfly" is called the "Old World Butterfly" in real life.

The tiger butterfly was shown in the Animal Crossing 3DS trailer. Although it cannot be confirmed that it will be featured in this game, it does seem likely.

Donating to the Museum
As with all fish and bugs in the, the Tiger Butterfly can be donated to the Museum by talking to Blathers, who will also tell the player a little bit about the donation. Regarding the tiger butterly:

In Wild World
Blathers will accept tiger butterflies for donation to the insect room of the museum, but this doesn't necessarily mean that he likes them:

"Tiger butterflies are named due to their distinctive tiger-like markings... I must say, I'd almost rather encounter a real tiger than one of these. Real tigers are nowhere near as... wretched."

The tiger butterfly can be found hovering around the flowers in the first room of the insect exhibit after donation.

In City Folk
After donation at the museum in City Folk, Blathers the curator will talk about the tiger butterfly:

"Aside from the south pole, one can find tiger butterflies just about anywhere on earth. Imagine these monstrous bugs flapping about the whole globe... The very thought robs me of sleep!"

The tiger butterfly can be found fluttering around the flowers on the lower tier of the insect room after donation.

Bug Encylopedia Information
In Wild World and City Folk players can access information about fish and insects in the menu. Regarding the Tiger Butterfly -

Further Information
Papilio machaon, the Old World Swallowtail, can be found throughout Asia, Europe, and North America. There are over 30 subspecies of Old World Swallowtail. It is a common butterfly that flies quickly. They are around 80 to 100 mm in length.

Etymology
Papilio is the Latin word for butterfly. The word machaon is derived from the Greek word mache, meaning 'battle' or 'combat'. In Greek mythology, Machaon was a son of Asclepius, the god of healing. He led an army in the Trojan war, fighting on the side of the Greeks.