According to an internet search, there is no butterfly that is so poisonous that it would kill a human. There are butterflies that are extremely distasteful to birds and other such predators due to the larva's consumption of poisonous plants. The Monarch butterfly is a well-known example of that. The larva eat milkweed.
No Butterflies are not poisonous to humans but can be poisonous to their natural predators. The Monarch Butterfly is the most common "poisonous" butterfly. While still in the larval stage they feed off the milkweed plant, causing them to become toxic. There are several different butterflies that do this.
no
yes they are poison
Anything that leads to survival and reproductive success is, generally, an intrinsic adaption. If a butterfly were to mimic another butterfly that was poison to it's predators then those self same predators would tend to leave the non-poison butterfly alone as well as the poison butterfly thus leading to survival and reproductive success for the mimic.
if you don't eat it?
it has poison on its wings
No.
No, it could not, because the poison was specifically designed to kill rats, and was developed as a rat poison/killer, not a human poison/killer. It would still be considered rat poison, even if the human died from the rat poison.
The butterfly in no way harms human activities. The butterfly is beneficial to humans because it helps to pollinate the flower.
No.
no geckos can not spit poison!
No, humans are not poisonious.
Poisonous butterflies live on poisonous plants and collect the compounds from their host when the are a caterpillar (larva). Poisonous butterflies are often imitated (mimicry) by non-poisonous species, so the difference is sometimes very hard to see.