Well i try to make fountain of youth potion but i need Green Swallowtail Butterfly my werewolf i hunting everyday but he only find the rarest insects but nothing from Green Swallowtail Butterfly i also put some boxes from buydebug for make more insects and i got every incest but nothing from Green Swallowtail Butterfly i also went to all vacation worlds but nothing so is there any place in Moonlight Falls that i can find them

This is why it's important to read what you say before you post.

Green Swallowtails are uncommon, base-game bugs. Those spawners are probably all over the place, so giving you a list would be pointless. I'd recommend putting a bunch of uncommon base game spawners on your home lot and letting them do their job. It might take a while, though, so you should also check the alchemy store while you're waiting. They usually carry alchemy ingredients, including insects (if I remember correctly).

The alchemy store doesn't sell insect but the Green Swallowtail Butterfly is also part of the alchemy spawner that becomes active around each alchemy station that is being used regularly. So, you'll eventually be lucky if you visit the elixir store regularly and use the alchemy station there. No need for incests or child sacrifices.

also, do some alchemy at the alchemy shop. This produces spawners, some of which spawn those silly butterflies. (which look really silly when they have spawned in the parking lot and are swarming all around the giant bat (by Esmeralda, here on MTS) which your sim has ridden over on.)