B. vagans are tough to molt sex unless there's a good picture. Even larger specimens have small spermatheca - try to get a closer photo, or reference the one I've linked below and make your own judgement. I'd guess female from this picture, but still, try to make your own judgement.
At that size iwould expect to see some darkened spermathecae but I don't see any. Of course, the picture could be clearer but I'm think it is male. Can you upload a better pic for more positive answer?