Male or Female?
Males have a small black spot on the top surface of the hindwing. Females do not.
You can see the spot when the wings are open; sometimes it's faintly visible when the wings are closed, too.
Males also have slightly thinner wing veins.
Although not evident in these pictures:
— females tend to be slightly darker than males.
— the tip of the abdomen of the male and female are visibly different.