I think the difference comes in the size. Females are usually bigger than males. According to my books, the bodies are yellow with a black midline. No reference to black bodies.

If the yellow bar across the back is solid, it is a male, if there are delineated yellow dots in the black field, it is a female. Hope this helps.

Mechelle

Could you show us some pictures that show the difference?

Maybe these photos will help.

Susan

Here is a link that might be useful: Male/Female Tiger Swallowtails

Thanks but I think the OP was asking about Giant Swallowtails. I couldn't find any info that mentions the yellow bar being different on males than females.

Oops, my bad; pbs (poor brain synapses) lol!

The horizontal bar that runs across the back is thicker on males than on females, and the oval shaped spots that also run horizontally are a little bigger and closer together. It's hard to tell the difference in the field, though, because the difference isn't all that great.
Here's a picture of a female giant swallowtail -
{{gwi:474261}}
And here's a picture of three males that had been "wing slapping" upward in a spiral, fighting I guess -
{{gwi:490789}}
And here's a picture of a mating pair - oddly, the female is on top -
{{gwi:506821}}
Sherry

That is awesome info, thank you!!

and, I have gender ID info on them when they are pupae on my Butterfly Guide...