Re: Why do multiple mutational fruit flies appear to have darkened wings?

This mutant's genotype sounds like (w m f), homozygous - in other words,
it's lost function in the genes white, forked, and miniature.

A search on Flybase (www.flybase.net) for miniature shows that the dark
wing phenotype is a common aspect of miniature mutations. So the miniature
wing mutation is probably responsible for the darkened wings.

The reason for this is that miniature encodes a protein important for wing
cuticle development, and when it is knocked out, the cuticle develops
abnormally. Debris from dead cells accumulates in the mutant wings; perhaps
this is responsible for the darkened appearance, though I'm not entirely
certain of that.

Sources:

www.flybase.net

Roch, F et al. (2003) Drosophila miniature and dusky encode ZP proteins
required for cytoskeletal reorganisation during wing morphogenesis. Journal
of Cell Science 116: 1199-1207