Signs Your Tarantula Is About to Molt

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Molting is one of the most fascinating and nerve-racking parts of keeping a pet tarantula. It’s a natural process that allows them to grow, heal, and even regenerate lost limbs. For newer tarantula keepers, it can be a stressful sight because a tarantula getting ready to molt can look sick, sluggish, or even disappear into hiding for months at a time. Understanding the process and recognizing the early warning signs helps you keep your tarantula safe and reduces the stress for both of you.

What Is Molting?

Tarantulas, like all arachnids, have exoskeletons, which means they wear their skeletons on the outside of their bodies. When that exoskeleton becomes too tight, they have to shed it in order to grow. This process is called ecdysis. Spiderlings molt frequently, sometimes every few weeks or months, while adults may only molt once a year or less. Adult males usually stop molting after they mature, which is known as their ultimate molt (and the molt directly preceding that molt is the penultimate molt). Before a molt, your tarantula will enter a phase called premolt. This is when you will begin to notice physical and behavioral changes that show the molt is coming soon.

Physical Signs of Premolt:

1. Dark, Shiny, or Swollen Abdomen

One of the most reliable signs that a molt is approaching is a change in the color and texture of the abdomen. As the new exoskeleton begins to form underneath the old one, the outer layer stretches and thins. This causes the abdomen to appear darker and sometimes glossy, especially in species that have kicked off some of their urticating hairs. The new cuticle developing underneath can give the surface a metallic or shiny look, and many tarantulas also appear plump or swollen at this stage. Imagine a grape, covered in hair, that is what it looks like. As molting gets closer, the dark patch on the abdomen often deepens to gray, blue, or nearly black, depending on the species. When the abdomen looks dark and shiny, the molt is likely only days away.

2. Reduced Appetite

As the tarantula prepares for the molt, its appetite naturally decreases. Internally, the process of forming a new exoskeleton requires energy and fluid shifts throughout the body. Feeding during this stage can be risky, so the spider instinctively stops eating. This fasting can last anywhere from a few days to several weeks, depending on age and species. I once had a Grammastola rosea (Rose Hair Tarantula) that went over a year without eating before she finally molted. So, refusal to eat is normal and should not be forced.

3. Lethargy and Hiding

Premolt tarantulas often become sluggish and seek out quiet, secure spots. They may retreat to their burrow or hide and stay there for long periods. Some species seal themselves inside with substrate and webbing to maintain the stable humidity they need for molting. This behavior is completely natural and not a cause for concern.

4. Increased Webbing or Burrow Work

Many species lay down a dense web mat right before molting. This mat provides traction for the spider to push against while working out of the old exoskeleton. Others reinforce the walls of their burrow or construct a silken retreat to molt in. This “home improvement” phase, in addition to the other signs, is a clear signal that a molt is approaching.

5. Duller Overall Coloration

In addition to changes in the abdomen's appearance, the tarantula’s overall color may fade. The legs and carapace lose their normal vibrance as the old exoskeleton prepares to split. The colors become faded, and blacks turn into grays or even dark browns. Once the molt is complete, the spider’s colors will return brighter and more vibrant than ever.

How to Help Ensure a Successful Molt:

Once you know that your tarantula is in premolt, there are a few simple but critical steps you can take to help them have a successful molt:

1. Keep Them Hydrated

Dehydration is one of the most common causes of molting complications. Always make sure your tarantula has access to a clean, full water dish. Even species from arid regions drink regularly, and a hydrated spider is far more likely to molt successfully. Slightly moistening one small corner of the substrate by overflowing the water dish occasionally in their enclosure can also help maintain humidity without making the enclosure too damp.

2. Avoid Handling or Rehousing

Handling a tarantula in premolt is very risky. Their exoskeleton is stretched tight and very sensitive, and even a short drop could rupture their swollen abdomen. If your tarantula is due for a rehouse, wait until after they have molted and hardened before moving them to a new enclosure. Stress is a major enemy during this stage, so limit vibrations, bright lights, and unnecessary disturbances.

3. Do Not Dig Them Out

If your tarantula has sealed itself into their burrow or web tunnels, leave them alone. This behavior is completely natural and helps them control the humidity and temperature they need for a safe molt. It also gives them a dark, safe place where they can relax and not worry about prey disturbing them. Trying to dig them out or “check on them” can destroy their carefully built environment and cause fatal stress.

4. Respect the Hunger Strike

When a tarantula refuses food in premolt, that is your signal to stop offering it. Forcing prey on them can lead to stress and even injury if the tarantula tries to defend itself. They will eat again when they are ready, usually after their fangs harden post-molt.

5. Remove All Live Feeders

Never leave live prey in the enclosure with a tarantula that is about to molt or is in the process of molting. Crickets, roaches, and even mealworms can attack or chew on the soft, immobile tarantula, causing serious injury or death. If you suspect your tarantula is close to molting, remove all feeders immediately.

6. Reduce Stress in the Environment

Keep the enclosure in a quiet place away from heavy foot traffic, loud noises, or vibrations. If they are in a room with a lot of activity, noise, and light, consider putting a towel or small blanket over their enclosure (if it is safe) or even consider moving their enclosure into a closet or a quiet room until after they have molted and hardened up successfully. Even minor disturbances can interrupt the molting process or cause your spider to panic at the worst possible moment.

The Molt Itself

When it is finally time, the tarantula will usually roll onto its back or side and remain still. This position can look alarming if you have never seen it before, but it is completely normal. They will slowly push themselves free from the old exoskeleton, beginning at the carapace and working out the legs. Depending on the size and health of the spider, the entire process can take anywhere from thirty minutes to several hours. Do not disturb your tarantula while it is molting. Avoid spraying, tapping, or moving the enclosure. Any vibration or interference could cause a fatal injury.

Post-Molt Recovery

After the molt, your tarantula will look brand new. Their colors will be brighter and their legs freshly stretched. However, the new exoskeleton and fangs are extremely soft at first. Avoid feeding or touching your tarantula until the fangs turn dark black again. Depending on size, recovery may take a few days for slings or up to two weeks for adults. Keep clean water available at all times, because tarantulas will usually drink soon after molting to rehydrate and expand their new exoskeleton fully.

When to Be Concerned

Even under perfect conditions, things can go wrong during a molt. Knowing what to look for can help you decide whether to intervene or simply give your tarantula more time.

Wet Molt

A “wet molt” occurs when humidity is too high or the tarantula has been kept on overly damp substrate. Try a well-draining bioactive substrate like The Bio Dude's Terra Aranea that's designed for tarantulas. The spider may appear shiny or slick during molting, and the old exoskeleton can cling to the body instead of sliding off. This makes it difficult for them to pull free and can lead to deformities, lost limbs, or even death. The best prevention is proper ventilation and balanced humidity. If a wet molt occurs, resist the urge to interfere. Allow the spider time to finish and dry out naturally. Unfortunately, during these vulnerable times, anything we do to help can be perceived as a threat by the tarantula, causing them to move to try to escape danger. This can be very disastrous for a soft, freshly molted spider.

Stuck Limbs or Abdomen Pieces

Sometimes pieces of the old exoskeleton remain stuck to a leg, the pedipalps, or the spinnerets. This is usually the result of dehydration or low humidity during the molt. Do not try to pull the piece off immediately. Instead, increase humidity slightly and leave the spider alone for a day or two. Often, the stuck material will loosen on its own. If it does not, you can use long tweezers to gently remove the dry fragment once the tarantula has fully hardened. In more severe cases, the leg may need to be lost, but it will often regenerate over the next few molts.

Stuck Inside the Molt

If your tarantula has been on its back for many hours without progress, it could be trapped inside the old exoskeleton. Increasing humidity and leaving the room dark and quiet are the safest options. If the spider remains trapped after an extended period and is clearly struggling, carefully moistening the old exoskeleton with a small brush or dropper may help soften it, but only attempt this as a last resort, and never touch the spider directly.

“Bleeding” or Fluid / Hemolymph Leaks

If you notice any fluid leaking from the body or limbs, your tarantula may have torn its soft exoskeleton. Applying a small amount of cornstarch or liquid bandage to the wound can sometimes stop the leak or hemolymph, but this is often a fatal injury. Prevention through proper hydration and low stress is far more effective than emergency intervention.

Final Thoughts

Molting is one of the most important and delicate moments in a tarantula’s life. It is a test of your husbandry, patience, and understanding of the tarantula's needs. When a molt goes smoothly, it feels like a victory for both you and your spider. But when it goes wrong, there’s often nothing you can do to reverse it or help them out.

Caring for tarantulas is a lot like growing plants. By the time a plant starts showing signs of disease or dehydration, the damage has already been done. You can’t fix it overnight, and sometimes you can’t fix it at all. Tarantulas work the same way, especially when it comes to molting. Once the process begins, the outcome is already determined by the conditions you’ve provided leading up to it. An ounce of prevention is worth far more than a pound of the cure, especially when there really isn't any cure. Proper hydration, stable temperatures, good ventilation, and minimal stress are the foundations of a successful molt. By the time you realize your tarantula is struggling, the die has already been cast. The best thing you can do is prepare in advance, maintain consistency, and let nature do what it’s designed to do. In most cases, our attempts to assist a tarantula's molt will cause more harm to the spider than help.

When that fresh, newly molted tarantula finally stretches its legs and shows off its vibrant new colors, it’s a reminder that all your attention and care have paid off. These animals may be slow-growing and secretive, but when they reward you with a flawless molt, it’s one of the most satisfying experiences in the hobby.