I desperately want a better word for butterfly than butterfly to use in this post. Butterfly is like the limpest name for a critter that, at least in my campaign, is big and scary and cast spells willy-nilly. Lepidopterans sounds too formal, and using foreign words just seems cheap. However, the Russian babochka is far and away the coolest sounding word for them I could find.
The wizards of Ig don't wear pointy hats. Wizards wear robes and capes and turbans and queer haberdashery of iridescent moth-wing This is because butterflies and moths are natural spell casters not out of any knowledge of their own, but due to the markings on their wings. The pattern of colorful scales on their wings form mandalas, sigils, and the true names of all things. A solitary normal butterfly or moth is harmless, but a sufficiently large swarm (rabble) resonates magically, so many wings brushing together builds up an esoteric charge that can be released at any shock to the group. The spells released scale in proportion to the amount of number of individuals in the rabble. A wizard wearing specially fashioned robes, cloaks, or masks will find his mystical abilities heightened by the wings.
Any gear crafted from butterflies or moths is lumped together in the catch-all of "moth-wing." This type of clothing can only be crafted by a wizard, and at no small cost. However, a wizard wearing a full suit gains a +3 to resist offensive spells and +3 to all spell checks as well as providing several mystical abilities. Moth-wing provides no bonus to AC.
Moth-wing Hat: Often taking the form of a turban bedecked in scintillating wings or simply the decapitated head of a giant moth hollowed out and made into a cap. A moth-wing hat provides a +1 bonus to all spell checks and saves. The wearer can also be used to cast Speak with Insects 2/day Cost: 400gp and 5 HD in butterflies/moths
Moth-wing Cloak: Usually made from giant wings sewn in a fashionably gaudy cape. A moth-wing hat provides a +1 bonus to all spell checks and saves. The wearer can also cast Color spray 1/day. Cost: 600 gp and 10 HD in butterflies/moths
Moth-wing Robes: A moth-wing hat provides a +1 bonus to all spell checks and saves. The wearer can also cast Featherfall 2/day. Cost: 900 gp and 15 HD in butterflies/moths
Butterfly Rabble: Init +4; Atk none (but see SP); AC 9; HD 1d8+; MV fly 40'; Act special; SP random spells, half damage from non-area attacks; SV Fort +0, Ref +6, Will +0; AL C.
For DCC the rabble can cast a random spell of a level up to the number of HD they have. It casts this spell with a spell check bonus equal to half its current HP. For mores standardized systems, consider it to have spell slots equal to a magic user of equal HD, with the spell taking up as many slots as possible.