This, by Melissa Kaplan, has all you need to know:
Uhm..there are several theories about finding out an ig's sex by looking at the igs, but IMO they all have a 50% chance of being right. The only physical characteristic of males I can trust a little is the presence of large femoral pores. But some females have big ones too. Both can have small ones, but many females's pores are barely there at all.
I suggest that if it's sex is ambiguous and an x-ray shows no eggs, to go ahead and make the
nesting bin just in case.