not until they get bigger or when they pair up from a group.
when fully grown the female is smaller and has a rounded look to the belly. the male gets a humped look to the head and a pinched look to the belly.
if they manage to pair from a group then the female just before she lays eggs has a short blunt breeding tube, whereas the male is longer and more tapered.
sometimes though if there isnt the choice of partner two females can pair up and lay eggs together.