Are Female Tarantulas Larger than Male Tarantulas? (And Why?)

When it comes to tarantulas, females are larger than males. Understanding this and some of the differences between female and male tarantulas is beneficial for keepers. Determining the sex of a tarantula can be tricky, but knowing this is crucial.

Female tarantulas are always larger than male tarantulas. The females are larger and bulkier than males, but they might have shorter legs. Male tarantulas usually have longer legs and look spindlier in comparison.

In this article, we will be covering everything related to why female tarantulas are larger than males and what this means for our pets. While females are heavier, they might not be ‘bigger’ depending on your definition.

Are Female Tarantulas Larger than Male Tarantulas?

Female tarantulas are heavier and bulkier than males. They have broader chelicerae in proportion to their body size than males have. Male tarantulas have longer legs than females giving them a leggier appearance.

Male tarantulas can sometimes look just as large or larger than females due to the long legs they have. Female tarantulas are recognised as being larger due to them having a much larger body and bulkier in comparison.

Why are Female Tarantulas Larger than Males Tarantulas?

The sexual dimorphism in tarantulas is advantageous. Smaller males can travel faster with their long legs, allowing them to hold her fangs out of reach while breeding. Larger females allow them to carry more eggs to produce more offspring.

Tarantulas have evolved with sexual dimorphism due to it working well for them. This means there are physical differences between males and females because this has helped tarantulas survive over millions of years.

There are multiple theories on why female tarantulas are much larger than males. Ultimately, it comes down to females carrying more eggs, but this alone doesn’t explain the massive size difference. Science now recognises it comes down to the males.

Why are Male Tarantulas Smaller than Female Tarantulas?

Male tarantulas are smaller due to it giving them an evolutionary advantage. Male tarantulas have a short life span, so they do not have the time to grow very big. They have longer legs to travel great distances quickly in search of a mate. Male tarantulas also use their long legs to hold the females’ fangs away during breeding.

Male arthropods don’t typically live very long, with male tarantulas living up to around 10 years maximum. This lifespan difference is due to males being more active, which means they have a higher metabolic rate ( Male tarantulas are usually only seen during mating season. They typically die shortly after, even if they’re well cared for.

Studies have shown ( that some males from spider species will use their long legs to fight with other males. Longer legs also allow them to travel great distances quickly, and the pedipalps on their front legs are used to hold the female up to reduce the risk of being eaten during breeding.

Why is there such a big size difference between Female and Male Tarantulas?

Being smaller is an advantage to male tarantulas but being larger is also advantageous to female tarantulas. Female tarantulas being large allows them to carry more eggs, but smaller males with longer legs let them move greater distances. However, male tarantulas have a faster metabolism than females, which means they don’t live as long.

If the size difference between male and female tarantulas were not advantageous, evolution would have eliminated it. Males being smaller makes them less of a target to predators when they look for a female to breed with. The small size and longer legs let them move great distances to find females with a lower risk of death.

What is the Largest Female and Male Tarantula?

The Goliath Birdeater (Theraphosa blondi) is the largest tarantula for both males and females currently known to us. Females are much larger and can reach a leg span of up to 30cm (12 inches).

The exact maximum size of male Goliath Birdeaters is unknown. However, we do know they have a shorter life span. Females of this species can live up to 20 years while males can live for 6 years at most (

Are Female Spiders always Bigger than Male Spiders?

Female spiders are usually larger than males, with some males being extremely smaller than their female counterparts. However, this is not always true. Male spiders from some species are bigger than the females.

While male spiders usually are much smaller, there are some species where this isn’t true. Diving Bell Spiders or Water Spiders (Argytoneta aquatica) have males as large or larger than the females. While the females range from 7.8 to 13.1mm, male spiders range between 7.8 to 18.7mm instead. This is due to large males having mobility advantageous over smaller males in dense water environments.


Female tarantulas are always larger than male tarantulas however, this assumption isn’t always true for all spiders. Male tarantulas are smaller with longer legs, so they can travel distances quickly while searching for a mate and protect themselves during mating. Larger female tarantulas can carry more eggs and produce more offspring. Evolution has favoured smaller males and larger females for tarantulas and most spider species.

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Stuart is the editor of SpiderAdvice.