Ok, so you often hear people asking: "Is my spider ready to breed" or "How big does my female spider have to be to breed?"
The usual answer you get is 75% of adult size.
Now while this might be true for most species, our local baboon spiders seem to be different.
Uncle scarab has recently sexed a few baboon spider moults for me and the results are quite surprising.
He sexed an A.junodi female for me this last weekend at 6cm and she was fully mature. The males of this species mature at around 4cm which would make mating quite a breeze (Even though the males of this species don't have mating spurs). Now what is strange about this you ask? Well, I have a junodi female around 14cm in legspan (And have seen some even bigger than this). That would mean that the females could possibly mature at around 35-40% of full grown size. Really fascinating. (To me atleast).
On the other hand, I have a few darlingi's and the one that scarab sexed for me was around 8cm and also a mature female. The males of this species mature at around 12-13cm, so the females would really be quite a bit smaller than the male if she were to mate at 8cm. The females do however grow to around 15cm which would kind of balance out the size difference. Even so, the females mature around 50% of full grown size.

Makes you wonder at what sizes spiders are able to really breed hey?

Anyone have similar stats on other species of tarantula?

Brachypelma albopilosum adult size: 12cm - 14cm

My MF is approx 8cm with egg sac - dropped 16 October 2011

Good thread.

We know when males mature because they develop clubbed pedipalps and some develop tibial spurs, but what about females?

Is it fair to say that if the spermathecae are visible on a female, she is already capable of mating even if the male is twice her size?

This is something I honestly don't know, when is a female mature? Care sheets often say species "x" is mature at "x" years... But what defines this? How do we know for sure that a female cannot be mated earlier?

Weird, this has never come to mind because naturally I have always accepted that the female must almost be full size before attempting a mating.

When breeding any tarantula size has never been an issue for me, rather the spiders sexual maturity. Studying the spermatheca is important and will give you an indication of how developed said female is. Some species I have bred at a small size compared to adult size is:
Avicularia "avicularia"
Brachypelma albopilosum
Brachypelma vagans
Psalmopoeus irminia
Psalmopoeus pulcher

Awesome thread Cerat, We always going on about the males but never the females.

I for one will be taking notes here

Thanks Hendrijs, can you give us some pointers or examples on when the spermathecae are developed/mature enough for a female to breed? Maybe even some picture comparisons?

Also what about attitude? Would a younger female be more receptive than an older female? Or no difference?