From Nookipedia, the Animal Crossing wiki
The Tiger Butterfly (アゲハチョウ, Agehachō) 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.
Donating to the museum
As with all fish and bugs in the Animal Crossing series, 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 Butterfly:
In Animal Crossing
"There's an old saying among some of my contemporaries: "Butterflies are beautiful, yet moths are monstrous." Well, if you were to ask me, I'd say they were all the same! By which I mean disgusting! Truly hoo-rrific, wot wot!"
In Wild World
Blathers will accept Tiger Butterflies for donation to the insect room of the museum, but this does not 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.
In New Leaf
Upon being donated, the butterfly can be found in the first room of the bug exhibit resting on flowers with the other butterflies. The exhibit has this to say about the Tiger Butterfly:
"The larvae of tiger butterflies feed on leaves of orange trees until the metamorphose. When they're threatened, they emit a foul smell from their antennae to protect themselves. The dusting you see on your fingers whenever you touch their wings is actually from their scales. These scales form the wing pattern as well as repel rainwater, making them very important for survival."
Bug Encyclopedia 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.
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.
Names in other languages