Sexing a Tarantula

Molt from an Aphonopelma seemanni.

Determining the sex of a tarantula can be one of those “can of worms” topics among some tarantula enthusiasts. Some say you can tell by looking at certain external features of the spider, but the most accurate method (and I think most would agree with this) is by looking at the molted (shed) skin of the tarantula.

Female tarantulas have small organs that store sperm after they have mated with a male. These organs are called spermathecae. If the molt of the spider is big enough (a magnifying glass or microscope may be needed), you can check for the presence of the old spermathecae – now shed by the spider. From there, it is simple:

Spermathecae = Female Tarantula

No Spermathecae = Male Tarantula

What you are looking at here is the inside of the abdomen portion of the tarantula’s molt. The four white patches are the spider’s booklungs. (They are folds of tissue that filter air, allowing the animal to breath.) In between the top pair of booklungs, you will see a groove, or slit. (It almost looks like a pair of lips.) Just above that grove, although difficult to see, is a flap with two brown spermathecae. (If you see the slit as a mouth, then the spermathecae look like the eyes.)

This Aphonopelma seemanni is a female.