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How to Tell If a Tarantula Is Male or Female

By Amy S. Jorgensen | Updated October 19, 2017

Determining the sex of your tarantula can be challenging. However, several key anatomical differences will make the job easier.

Subtle Differences

Generally, tarantula females are larger and bulkier than males. If these are your first tarantulas or if you do not have a spider of the opposite sex for comparison, sexing based only on your spider’s size can be difficult. Similarly, female tarantulas have broader chelicerae, her jaws or fangs, than males do in proportion to their body size. But without previous familiarity with tarantulas and/or other spiders for comparison, you can't rely on this detail alone to sex your spider.

Mature Male Differences

If you wait until your tarantula matures, sexing him or her will be easier. Mature males have a hook on the underside of their front leg. These hooks keep the female's fangs away from the male during mating. Mature males also have bulbs on their pedipalps, the two shorter, leg-like feelers located near their fangs. These bulbs are the male spider's sex organs.

Molted Skin Differences

For owners who want to sex their tarantulas early, the task requires taking a closer look at the spider’s molted skin.

Carefully, smooth out the skin around where the spider's abdomen would have been. You should see four white spots at the top of this area. Those spots represent the discarded lining of the tarantula's lungs. Between those spots you should see a crease. If the crease has a roundish bump emerging from it, you are looking at the skin of a female tarantula. The bump is the female's spermathecae where she stores the male's sperm after mating. Male spiders will not have that bump.

Extra Spinnerets

Another difference you can often see in male tarantulas is the presence of epiandrous fusillae, additional spinnerets believed to be used for spinning a sperm web where they deposit their sperm so they can then take it into the sex organs on their pedipalps. If you gently flip your tarantula over and examine its abdomen, you will see a line called the epigastric furrow across the abdomen. Just above that line, you may see an arched or semicircular area. That area is epiandrous fusillae, which means your tarantula is male.


Amy Jorgensen has ghostwritten more than 100 articles and books on raising and training animals. She is also an amateur dog trainer. She has also written more than 200 blog posts, articles, and ebooks on wedding and party planning on behalf of professionals in the field.