Thanks duke. But it doesn't answer the question. If you open a pupae there's nowt inside but a soup of stuff, somehow something just does whatever, and a moth appears, so is the dna apparent at the caterpillar stage, or does it happen at the big bang part..
Internets don't help, but there's a plethora of incredibly intelligent people here, and possibly a lepidopterist.
(lordy lordy, Fri 14 Oct 2011, 19:01, 1 reply)

Well, you learn something new every day*.
I thought that sex was likely determined by then, but wasn't completely sure so I googled it.
Turns out that butterflies have a Z chromosome and an X chromosome (both passed on by the mother) and presence of both means female and one of each means male.
Source: biology.about.com/od/basicgenetics/p/chromosgender.htm
*At least I do**.
**Well, OK, not every day but quite often.
(Me, I'm not... in any way intoxicated, Fri 14 Oct 2011, 21:00, closed)

So...how do you determine
if you have both kinds of chromosome, or merely one of each?
(Falstaff's Spiritual Successor, Fri 14 Oct 2011, 23:30, closed)

doh
I, of course, meant only Z means male and both means female.
(Me, I'm not... in any way intoxicated, Sat 15 Oct 2011, 0:18, closed)