When the butterfly dies and is raised from the dead through Egyptian black magics, it returns to this mortal plane as the moth. It may resemble the butterfly you once knew, but remember – he’s dead now. What you’re seeing is a monster.
Perhaps you doubt this. Perhaps you believe that the moth is in fact a living creature of its own, distinct from the butterfly. I would ask you to try killing a moth yourself. You will find that, when the demonic fire keeping the moth going is snuffed out, its body will be reduced to dust. Yes, dust just like the vampires in seminal genre television series Buffy the Vampire Slayer.
There are, believe it or not, a number of ways in which the moth is different from the vampire. While neither beast needs to eat to sustain itself, the moth does not feed on blood.* The vampire burns up in sunlight, whereas the moth only grows weak and nauseous. The vampire can be killed through a wooden stake to the heart or beheading, but the moth is vulnerable to most any traditionally mortal wound. It is, however, immune to all forms of disease.
If you have seen the moth in person, there is little doubt that you have seen it careen toward a light source. It may appear to be a suicidal and unrequited love affair between moth and lamp, but the moth’s actions are not illogical. The moth does not die when it touches a hot light because it knows how to travel the subspace pathways that link all incandescent bulbs.** Any moth body that remains in this dimension is a mere husk, which will be easily replaced when the moth reaches its destination – which may be your home!
Also, as mentioned above, the moth can not be felled by disease.
Again, the moth weakens in sunlight. It is also, honestly, not that great at flying.
Number of legs
Life cycle notes
A cursed butterfly does not immediately emerge from its grave as a moth. First, it wraps itself in a cocoon made of pure silk. Within this structure of its own (or Ed Hardy’s) design, the corpse transforms into its new unholy form. After six nights, the moth breaks free, leaving behind silk which can be harvested by clothing manufacturers. This is why silk workers are no better than war profiteers.
Horrifying Wikipedia quote
“Grease Moth (Aglossa cuprina), known to have fed on the rendered fat of humans”
What if it fought a bear?
The moth may be an abomination, but it is not terribly powerful. The bear would destroy it and become a hero.
Is it noble?
The moth is a disgusting perversion of a good animal. A twisted funhouse mirror image. It does not have the strength to execute much in the way of evil, but its corrupting influence is enough to condemn it.
*Well, not usually.
**Thanks, Thomas Edison!