Is it male or female?
This is often one of the biggest questions that goes through a keepers mind when acquiring a new tarantula. Females are prized among hobbyists for their larger size, longer lifespans (some species can live decades!) and ability to produce eggsacs. Males are often requested for breeding projects or for those who want a pet with a lifespan (and commitment) of a only few years. Determining the sex of a tarantula can be tricky though, especially when it is younger as male and female tarantulas will often look and act extremely similar until mature.
How can you determine the gender of a tarantula?
The ONLY way to absolutely know the gender of a specimen is to look at it’s molt/exuviae.
The other, and not so reliable method is by looking at the tarantula itself, either ventrally (underside) or dorsally (topside) which we’ll cover later in this article.
What about spiderlings?
With over 35 years combined tarantula keeping experience we still do not know of any method to determine the gender of spiderlings. If we come across even semi-reliable method to sex spiderlings I will update this article with instructions.
So how do I molt/exuviae sex a tarantula?
By using the tarantulas exuviae (also: exuvium) also known as a cast skin or molt. Exuviae sexing, also known as molt sexing is the most reliable way to confirm the gender of a specimen and the only tried and true way to absolutely confirm the sex of larger, immature or mature specimens. In order to properly determine the gender first you will need an intact molt.
Getting an intact, read-able molt is a feat in itself… You must be quick to grab the molt soon after the tarantula has shed it’s skin or else the tarantula is likely to much on it. Bon appétit!
If the molt gets eaten you’ll have to wait until next time for the chance to revel it’s gender.
Not all tarantulas will much on their molt however, if the molt is recovered quickly after the tarantula has shed not only will the molt be soft and pliable (which makes the next step much, much easier) but you won’t give him/her the chance to eat it.
If you are able to get to the molt before it’s eaten be extremely careful not to disturb the soft and very vulnerable tarantula!
I have the intact molt, now what?
Is the molt soft? If not take care not to break it (the molt will crumble easily when completely dry) soften it in some warm soapy water for 15-90 minutes, or overnight. How long it needs to soak depends on how large and how dry it is. Make sure the molt is completely soft before proceding.
With the molt pliable, carefully unwrap the abdomen section. Examine the molt to look for the presence of a spermathecae. This female reproductive organ is where sperm is stored until the eggs are laid.
While a female can be identified by the confirming the presence of a spermathecae, a male can be identified by confirming the absence of a spermathecae.
The spermatheca is located between the first pair of book lungs.
Pictured below is a female Grammostola porteri (Rose Hair). The spermathecae is being manipulated with a toothpick.
The same molt (Female G. porteri) approx. 5 1/2″ DLS. The spermathecae is highlighted in red (below)
Now compare these females molts to that of a male Avicularia (Pinktoe) below.
The Looking Methods
So, you don’t have an intact molt handy? Be advised the looking methods are not very reliable, can not be used on spiderlings and small juveniles as the smaller specimens look more or less the same (at least to me…)
The exception to this rule is mature males as once a male has reached his mature (also known as “final” or “ultimate” molt) he can be easily identified and his gender 100% confirmed by the presence of his male reproductive organs.
You can use the looking method to visually sex the actual tarantula two ways, by ventral sexing, that is looking at the tarantulas ventral side, the underside of it’s abdomen or by dorsal sexing, this is looking at the tarantulas dorsal or back/top side.
Ventral comes from latin venter meaning belly, stomach or womb. Dorsal form the latin dorsum meaning back and/or ridge of a hill.
We do not use the looking methods to determine gender here at Jamie’s Tarantulas with the only exception of “suspect, not guaranteed males” offered every-so-often. Although the looking methods are not considered to be completely accurate the topic still be covered in depth as to help others to make educated guesses as to the gender of their specimen, at least until an intact molt/exuviae can be recovered.
Ventral Sexing It is possible to make an educated guess at the specimens gender by examining the ventral side of the abdomen. You’ll want to try this with tarantulas minimum about 2″ DLS Ventral sexing is not considered an accurate way to determine gender however, most often the specimens intact molt is not immediately available and we must rely on what we have and accept the answer will only be a “best guess”
Some advice for those wanting to ventral sex: Getting good at ventral sexing is something that comes with experience. No one starts off good at it, In my early hobby days can recall going crazy because I couldn’t detect any difference. I can tell you the more you practice, the better you’ll get! Look at lots of tarantula undersides. It will become easier and easier!
Here is an Aphonopelma chalcodes (Arizona Blonde) 4 1/2″ male first unedited:
Here are some easy-to-spot visual characteristics between mature males and mature females
…that don’t require looking at their underside.
When a male matures (has his final or “ultimate” molt) he gains some distinguishing characteristics such as “tibial hooks” (present in most species) and bulbous pedipalps which are often referred to as “boxing gloves”
Mature Male C. cyaneopubescens (Green Bottle Blue) “Boxing gloves” are circled left & tibial hooks are circled right Also notice the lankier overall appearance, including longer legs and smaller, more narrow fangs of the mature male…
Mature Male C. cyaneopubescens (Green Bottle Blue) below:
Dorsal sexing immature specimens:
Larger juvenile and sub-adult specimens can sometimes be identified by their “body type.” Just like the adult male GBB and B. hamorii/smiti adults pictured above immature males typically have a lankier overall appearance including longer legs and smaller, more narrow fangs when compared to the females same size DLS. Be aware that females of most species go though a leggy adolescent phase and can be sometimes be mistaken for males during their “awkward teenage” years. Occasionally I might see an unusually stocky immature male.
We hope you found this article useful!
-Jamie
For those looking to purchase from Jamie’s Tarantulas:
If the gender of the specimen is known it will be included in the title.
If the gender is unknown no gender will be stated and the specimen will be sold as “un-sexed”.
Those tarantulas are sold as “unsexed” because we are unable to determine, or even guess their gender at this time.
We do not attempt to “pick out” females or males from the “unsexed” specimens.
Your chance of getting a male/female is roughly 50/50 with an “unsexed” specimen.
Leave a Comment - Reply to