Tarantula Molting Guide
Molting is one of the most important — and most misunderstood — events in a tarantula's life. It is how they grow, replace damaged limbs, and renew their exoskeleton. Understanding the molting process helps you avoid the most common keeper mistakes and gives your tarantula the best chance of a successful molt every time.
What Is Molting?
Tarantulas, like all arachnids, have an exoskeleton — a rigid outer shell that does not grow with the animal. To increase in size, a tarantula must shed its old exoskeleton entirely and expand before the new one hardens. This process is called ecdysis, or molting. A tarantula will molt dozens of times over its lifetime, with frequency decreasing significantly as the animal matures.
How Often Do Tarantulas Molt?
Molting frequency depends on age, species, temperature, and feeding rate. Spiderlings may molt every few weeks. Juveniles typically molt every 1–6 months. Adults of slow-growing species like Grammostola and Brachypelma may only molt once every 1–2 years. Faster-growing species molt more frequently at all life stages. Growth rate — and therefore molting frequency — is influenced by temperature and feeding. While heavier feeding can lead to faster growth in juveniles, intentionally overfeeding is not recommended because it increases the risk of obesity and husbandry issues.
Signs a Molt Is Coming
Pre-molt can last anywhere from a few days to several months depending on the species. Common signs include:
- Refusal to eat — often the first and most reliable sign
- Lethargy — reduced movement and activity
- Darkening abdomen — the new exoskeleton forming underneath causes the abdomen to appear darker or more matte
- Sealing the burrow or hide — many species web over their hide entrance before molting
- Flipping onto the back — the spider will roll onto its back when the molt begins; this is normal and not a sign of illness
Do not attempt to right a tarantula that has flipped onto its back. This is the molting position and interference can be fatal.
The Molting Process
Once the molt begins, the tarantula lies on its back and begins to work free of the old exoskeleton. The process typically takes 15 minutes to several hours depending on the size and age of the spider. Older, larger tarantulas generally take longer. The spider will flex and pump fluid to split and shed the old exoskeleton, starting from the carapace and working down through the legs and abdomen.
Do not disturb the spider at any point during this process. Even well-intentioned intervention can cause a limb to be lost or the molt to fail entirely.
What to Do During a Molt
- Remove all live prey from the enclosure immediately when pre-molt signs appear
- Leave the water dish in place — the spider may need hydration
- Dim or cover the enclosure if it is in a high-traffic area
- Do not handle, feed, or disturb the spider
- Do not attempt to assist a tarantula during a molt. Intervention should only be considered by experienced keepers in exceptional circumstances.
Post-Molt Care
After the molt is complete, the spider's new exoskeleton is soft and vulnerable. This is the most dangerous period — even a cricket left in the enclosure can injure or kill a freshly molted tarantula. Follow these steps:
- Wait at least 48–72 hours before removing the shed exoskeleton (the molt)
- Wait until the fangs have fully darkened before offering food. For many species this is around 1–2 weeks, while large adults may require longer.
- Do not handle the spider for at least 2 weeks post-molt
- Ensure fresh water is available throughout the post-molt period
- The spider's colors will be more vivid immediately after molting and will settle as the exoskeleton hardens
Failed Molts
A failed molt occurs when the spider cannot fully shed its old exoskeleton. Common causes include low humidity, dehydration, disturbance during the molt, or underlying health issues. Signs of a failed molt include a spider that has been on its back for an unusually long time (more than 12–24 hours without progress), or a spider that appears stuck with legs or abdomen still partially encased in the old exoskeleton.
If a tarantula experiences a failed molt, keep the enclosure quiet, ensure fresh water is available, and avoid further disturbance. Intervention is rarely successful and can easily worsen the situation. If you are considering assisting a failed molt, seek guidance from an experienced keeper or exotic veterinarian first. Prevention is far better than intervention — ensure the enclosure has an appropriate moisture gradient and a water dish is always available.
Saving the Molt
The shed exoskeleton (called the molt or exuvia) can be used to sex your tarantula. Female tarantulas have a spermatheca — a small reproductive structure visible on the inside of the abdomen portion of the molt. Flatten and dry the molt carefully, then examine the abdominal section under magnification. A fresh molt is much easier to unfold while still slightly damp than after it has completely dried. This is the most reliable way to sex unsexed juveniles and adults.
Molting and Regeneration
One of the remarkable aspects of molting is that tarantulas can regenerate lost limbs. A leg lost to injury or autotomy (self-amputation as a defense response) will begin to regrow at the next molt, appearing smaller than the others. It will continue to grow with each subsequent molt until it matches the remaining legs. Lost pedipalps and other appendages may also regenerate over successive molts, although complete recovery depends on the age of the tarantula and the severity of the injury. This process takes several molts to complete in adults but is faster in juveniles that molt more frequently.