Chrysalis question

[Cate]

I have an overwintering spicebush swallowtail chrysalis. What factors are
necessary for this chrysalis to transform into a butterfly? Is it
temperature, day length or something else? A friend in Florida has noticed
that her Polydamus chrysalides have taken twice as long to develop into
butterflies in the last month than they do in summer and fall. Since they
are kept at a fairly even temperature (indoors), it doesn't seem that would
be a factor.Would appreciate any input you have to offer.

Cate