off topic query

[viridian]

hi,

i have what might seem like a stupid question and i hope i'm not 
bothering you folks by posting it here, but i tried to research it on 
the net and didn't come up with much. can anyone tell me (or point me in 
the direction of an explanation) what the composition of butterfly 
pigmentation is?  as someone who is completely in the dark about 
butterfly biology, and butterflies in general, i'm not sure that i'm 
even phrasing the question properly. i was just curious as to what the 
powdery stuff is on their wings that makes their individual markings 
appear yellow or blue, for example, to the human eye.

thanks!

hilary
viridian at pipeline.com