wow thats a great camera! the picture is of a female. that last visible "segment" is not really a true segment i dont think, it will get covered up by the second to last visible segment (the one with the tiny little "notch" at the tip but no "spike") after a couple of moults. i have no idea why, maybe that last visible "segment" in your picture somehow becomes an internal part of the genitals? i dont know.
here is another picture of a female of your age (i think):
eventually the last (6th) segment you see will be the big one in the middle of the photo (if that make sense?). here is a picture of a female at fourth instar, you can see now the segment has basically grown over the little one you can see in your picture, and the sex is now alot clearer.
here is what males look like at the same age as your photo:
and at fourht instar:
as you can see the males have one last little spike (where the females have only a little notch). hope this helps.