Grammostola rosea [ventral sexing]

Waaaaay too small to tell. G. rosea take a very long time to grow, so you're in for a bit of a wait. It'll be with you for a long time, male or female.

@Arachnophoric Yes, it is a very small sling. On the other hand, the location and position of the book lungs dont really change over time so I figured the upper two and the spacing between them looks more like it would develop into a epiandrous fusillae.

@Tarantula Japan They do though, particularly from this size. As the T gets larger the shape, length, and position can change, and the area can look pretty diffeent depending on how well fed or recently molted the T is. That's why some genera/species - C. versicolor, for example - are very hard to ventral sex up until a certain size, in which they become incredibly easy to ventral sex. Trying to tell with your sling based on the shape/width/position of the furrow and epiplate with how small it is will not be an accurate thing to guess off of for another few molts. I wouldn't even bother trying until the sling is over 4cm in leg span, which is still small enough that any guess should be taken with a grain of salt. And that's saying something, since ventral sexing is still dubious at best. There are some Ts that will throw you for a ringer, even when you're dead-sure you knew the sex based on the ventral.

@Arachnophoric
Thank you for your detailed reply.
I was unaware that the position of the book lungs actually change over time.
I do have experience raising a C.Versicolor from a tiny sling but never tried to ventral sex it, mostly because of its webbing.
Im still curious how some people manage to ventral sex a sling. Although it may not be 100%accurate, some do a very good job at it.
Is it better with a micro lense mybe?
I wonder which parts they exactly examine..
Still lots to learn ^^;