Early Sex Determination of Tarantulas

[Inflammation]

Hello all arachnid keepers&breeders,

While raising tarantulas, I’ve always wondered how early they could be sexed.

There are some good posts here tackling this issue,
and I wanted to share my experience with sexing tarantulas.

I use a microscope to observe molts, with x40 ~ x500 zoom.

As a fan of Aviculariinae, I mostly keep pinktoes and close relatives.
I’ll start this post with them, and finish with big and scary species including Xenesthis and Pamphobeteus.


Avicularia, Iridopelma, Ybyrapora, Pachistopelma, Caribena etc. all can be sexed in the 4th instar (using the molt from the 3rd instar).
At least x100 zoom will show clearly a pretty spermatheca. (still detectable at x40)
The 1st~2nd molts do not show any difference between male / female.

1. Iridopelma cf. oliveirai (ex. ‘Encantada’) 4th instar, female


x40

x100

x200

x500

2. Iridopelma cf. oliveirai (ex. ‘Encantada’) 4th instar, male



x40

x100

x200

x500


As shown in above images,
females have prominent spermathecae and external uterus.
With growth and maturation, the spermatheca will get bigger and longer, exhibiting numerous bumps all over it, while the external uterus also gets large enough to cover the spermathecae.

On the other hand, males do indeed have structures that sometimes may resemble those of females,
but are much smaller and lack an external uterus.
Mostly, it appears sort of like a face,
with gonopores on the sides and a fish-mouth resembling structure in the middle.

 

[Wolfram1]

great pictures and demonstration

could be very useful as a reference in the future though most people probably wont have the means to check as early as you have demonstrated now.

still, thanks

 

[MariaLewisia]

Fully agree with your conclusions! Great pics!

 

[Ultum4Spiderz]

Impressive!!! I gotta wait until 2-3” too guess the sex of mine . I don’t know about pamphos being scary lolz.. mines pretty laid back . My g rosea was more defensive when I had it rip.

 

[fq314]

Nice pics.

 

[spideyspinneret78]

I also use a microscope to sex mine and have come to similar conclusions on when they can be sexed, depending on species. Great photos! This will be a helpful resource since microscope molt sexing resources can be difficult to find.