Quick Take
- Tarantulas molt by shedding their exoskeleton, allowing them to grow larger and develop stronger protection.
- Molting allows tarantulas to develop better armor, but they are vulnerable during the process.
- The pre-molt phase involves specific behavioral shifts that signal the start of the cycle.
Molting is one of a tarantula’s greatest superpowers. They shed their old skin to become something bigger, stronger, and more mature. As this happens, the spider undergoes a transformation few have the chance to witness. This is how it happens, and why it’s such an incredible process to watch from start to finish.
Why Tarantulas Molt Their Old Skin
Like many arthropods, tarantulas require new exoskeletons as they grow. Their bodies require space to expand and flex, which would be impossible if they kept the same skin their entire lives. Younger tarantulas may molt several times throughout their juvenile life, while mature adults molt once every year or two. After reaching maturity, female tarantulas may continue to molt periodically throughout their lives. In contrast, mature males typically molt only once more, if at all, before dying.
Male Mexican red-knee tarantulas typically do not molt after reaching sexual maturity, which occurs at around 4 to 5 years of age.
©Dean Pennala/Shutterstock.com
Although the process sounds complicated, it’s natural for the spider. The actual shedding of the exoskeleton can take anywhere from 15 minutes to several hours. However, the entire molting process, including preparation and recovery, may take longer. During that time, tarantulas often end up in strange-looking positions. This may include lying on their backs or sides, depending on how they shed their exoskeleton. Once the process is complete, the tarantula has a new layer of armor, while the old exoskeleton remains behind, resembling a smaller, lifeless copy of the spider. The shed exoskeleton serves no purpose afterward, but some tarantulas may curl up on top of it or move it around their enclosure. In the wild, a molt is often left behind as the tarantula moves on.
The Signs of a Tarantula Preparing to Molt
Before molting, tarantulas give clear signals. Most of the time, they’ll stop moving and become relatively still. They may lie on their backs, which is often mistaken for a tarantula that’s dead or dying. The difference is that molting tarantulas will not have curled legs. Tarantulas also do not eat when they’re about to molt, and a decrease in appetite is entirely normal.
Most tarantulas leave their molts behind and don’t have any use for them.
©Cornel Constantin/Shutterstock.com
Slow-moving tarantulas may also be preparing to molt. This behavior is temporary, and it will soon become clear whether the tarantula is molting or experiencing an illness. Another telltale sign is balding: tarantulas preparing to molt may have bald spots. These can appear in various places on their bodies but will disappear after shedding their skin. Discolored or faded skin is also a sign that a tarantula is molting, as the old skin loses its vibrancy. Increased webs or silk-spinning are another common sign, and some tarantulas may even sit in their webs as they shed their skin.
