Banded and Hickory Hairstreak  - male and female
Banded Hairstreaks, male (L)  female (R)

Hickory Hairstreaks, male (L)  female (R)

(1) the red spot above the large blue spot in the hindwing is smaller in Hickory (male and female), and the black basal area within the spot much bigger, making the red portion smaller.  This makes the blue spoy appear larger, but may be an illusion.

(2) The antenna on the female Hickory tends to have the underside (nudum) more extensively pale, often completely orange, but this appears to be somewhat variable.

(3) The scent gland on the forewing of the male, is long and narrow on Hickory, and broader on Banded.

 Many ID points can be variable, and some only call them "tendancies", but if you can put a good combination of these points together I don't hesitate to call it a Hickory. The one point that is completely unreliable is the offset in the fore-wing band. I chose the pictures to illustrate this. Some you just have to walk away from. There are some lepidopterists that will not accept a record of Hickory Hairstreak without a specimen and examination of the genetalia.