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Why Do Spiders Molt?

Spiders molt because they grow out of their exoskeleton. They need to adapt their exoskeleton to their growth, which allows them to become bigger and stronger.

Why Do Spiders Molt

Younger spiders molt more frequently than older spiders, as they are still growing and developing. When they’re young, they might molt once a month, which diminishes in frequency as they grow older. Molting is an adaptive behavior that allows the spider to grow and develop both sexually and physically.

Why Do Spiders Molt?

Molting is a necessary and frequent process for spiders that allows their exoskeleton to adapt to their body’s growth. 

Think of it like buying new clothes for children as they’re growing up – molting is a bit similar to that. The main difference is that the exoskeleton acts as a protective measure for the spider, as they don’t have an internal skeleton.

The exoskeleton of the spider wraps around its body and protects the internal organs of the spider. Without it, the spider would not be able to survive for very long. It is made of chitin, which is a strong compound that protects the spider from predators and provides structural support for the body of the spider.

As spiders grow, the exoskeleton does not grow together with the rest of the body. It’s made of rigid materials, which means it will not grow like the rest of the body, which forces the spider to molt.

This is one of the biggest drawbacks of the exoskeleton, as it does not grow as bones do in humans as we grow up, for instance. For this reason, the spiders will need to leave their old exoskeleton behind and start forming a new one that will allow the rest of the body to fit into the skeleton.

Related: Do Spiders have Bones?

How Do Spiders Molt?

The spider lies on its side, and at first slowly peeling its legs out of the skeleton as it wriggles its way out of the old skeleton. Slowly, the spider will crawl in its entirety out of its body, as it is a process that might take up to three hours to complete.

After the spider leaves its old exoskeleton, it will leave the skeleton right where it started the molting and a new and improved exoskeleton will start forming. A study has shown that a spider’s exoskeleton has an oil-like structure if it’s broken down, as the remains of the skeleton float on the water.

Most males and females will molt more frequently until they reach sexual maturity, which is at around age three to five. After that, most spiders will molt once a year, which is a necessary process to renew their exoskeleton and make it more powerful and effective again to protect the spider against predators.

The new skeleton might take some time to form completely and start to harden up. This process might take up to several hours to even several weeks, depending on the size and age of the spider. The faster this process is complete, the sooner the spider can return to normal life.

Is Molting Painful to Spiders?

Molting itself is not painful to spiders. They’re able to get out of their exoskeleton unscathed for most of the time, although it might take them a long time to do so.

The main issue after molting is the fact that spiders are vulnerable right after the process. That’s because spiders don’t have the same protection as they had before. After all, they lose the protective shield that was guarding them before.

This means that a spider might stay in hiding for a few hours or days after the molting. This is because they need to protect themselves fully against potential threats that arise because they’re not fully protected. Their exoskeletons are slightly compromised and not fully developed just yet.

Up to 85% of all spider deaths occur right after molting as this is when most predators are looking to strike. They know that the spider has compromised defenses and they’ll take every opportunity to strike and take advantage of the lack of protection from their exoskeleton.

How Long Does it Take for a Spider to Molt?

The molting process might take up to three hours to complete and sometimes even longer, especially if the spider is larger in size.

Then after molting has been completed, the spider will take a few days or even weeks to rest up and let its new skeleton fully grow. This process after molting is crucial for the spider and it might take a rest for the next few days just to make sure it’s not captured by a predator looking to strike.

Altogether, if we include the period after molting, the whole molting process will take up to several days to complete. The after molting process is crucial for the survival of the spider.

How Many Times do Spiders Molt?

Spiders molt multiple times in their life, and when they’re younger, they might molt every month or even more frequently which allows them to grow.

Older spiders, on the other hand, might only molt once a month or once in a few months. In one lifetime, a spider might molt more than 50 times altogether, while some spiders might molt even more times than this, which allows them to grow faster.

The number of molts is higher when the spider is younger, which is why it will need to molt more frequently as it is still developing and growing up. It will take more than 20-30 molts for the spider to fully grow up and develop completely as a mature and adult spider.


The molting procedure is necessary for the spider, as it allows the spider to grow quickly and develop an exoskeleton that will protect it. As the spider grows, it will need its skeleton to adapt to its growth to provide full protection to the spider.

Even though the molting doesn’t hurt the spider, it makes it vulnerable to potential attacks from other animals. That’s why the spiders exercise a high level of caution right after molting to avoid getting eaten as it does not have a high level of protection anymore.

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