The common names in English, fly agaric or fly mushroom, are generally thought to derive from its European use as an insecticide, sprinkled in milk.[1] This interpretation is supported by the mushroom's names in a number of other languages (see below), e.g. French Amanite tue-mouches, i.e. "fly-killer amanita". The fly-killing agent is now known to be ibotenic acid.[2] Another compound isolated from the fungus is 1,3-diolein which is an insect attractor.[3] [4] An alternate derivation proposes that the term fly- refers not to insects as such but rather the delirium resulting from consumption of the fungus. This is based on the medieval belief that flies could enter a person's head and cause mental illness.