FWD:

[Herbert Eichenseer]

Hi,

The following references may not be specific for butterflies, but may be
good sources for understanding the physiology of insect development:

P.O. Lawrence, "The making of a fly"

and 
F. Nijhout, "Insect Hormones".

These will give you a very good start, if you can find, them.  Certainly
at the U.C. Irvine library.

Herb

Herb Eichenseer <HEICHEN at COMP.UARK.EDU>
Department of Entomology
University of Arkansas
321 Agriculture Building
Fayetteville, AR 72701
501-575-2451