What Humidity Does a Tarantula Need to Molt Safely?
Tarantulas are low-maintenance until they molt, and then they need you to do almost nothing perfectly. Molting is how a tarantula grows, shedding its entire exoskeleton in a process that leaves it soft, defenseless and slow to harden. Knowing the signs and resisting the urge to intervene is the core skill. Get humidity right for the species and leave the spider alone, and most molts go fine.
What humidity and temperature do tarantulas need?
Keep most tarantulas at 70 to 78F, comfortably room temperature, with no heat lamp. Humidity depends on origin: arid species like the Chilean rose hair want 50 to 60 percent, while tropical species like the pink toe want 70 to 80 percent. Research your exact species, since the wrong humidity is a leading cause of molt and health problems.
Tarantula care is species care. A desert species kept too wet can develop fungal issues, while a rainforest species kept too dry can fail to molt. Humidity is usually managed through substrate moisture and a water dish rather than misting, which many keepers avoid to prevent mold. A digital hygrometer helps, but for most species a slightly damp substrate corner and fresh water are enough.
How do you know a tarantula is about to molt?
Pre-molt signs include refusing food for days or weeks, a darkening or balding patch on the abdomen, lethargy, sealing itself into a burrow, and webbing a molt mat. The clearest sign is the spider lying on its back or side. At that point it is molting and must not be touched, fed or disturbed until it has fully hardened.
A tarantula on its back looks alarming to new keepers, who sometimes assume it is dying and flip it over, which can kill it. This is normal molting posture. The spider pumps fluid to split and shed its old exoskeleton, then slowly works free. The process can take hours. Remove any live prey immediately, since even a small cricket can injure a soft, defenseless tarantula mid-molt.
How long after a molt can you feed a tarantula?
Wait until the new exoskeleton hardens, typically 1 to 2 weeks for spiderlings and 2 to 4 weeks or more for large adults. Right after a molt the fangs are soft and the body is fragile, so feeding too soon risks injury. The spider will not need food until it hardens, so patience costs nothing and prevents a serious mistake.
Fang hardness is the gate. A freshly molted tarantula cannot safely subdue prey, and a cricket left in the enclosure can chew on the soft spider. Watch the fangs darken from white to black as a rough readiness cue, and start with a single appropriately sized prey item. Always keep a shallow water dish available, since hydration matters more than food during this recovery window.
What are the target ranges by tarantula type?
Use species type as your guide: arid and desert tarantulas want 50 to 60 percent humidity and a dry substrate with a water dish; tropical and arboreal species want 70 to 80 percent and a damp substrate. Temperature for nearly all common pet species sits at 70 to 78F. Always confirm the exact requirements for your species before setup.
| Type | Humidity | Example species |
|---|---|---|
| Arid / desert | 50 to 60% | Chilean rose hair |
| Tropical terrestrial | 70 to 80% | Brazilian black |
| Tropical arboreal | 70 to 80% | Pink toe |
| Temperature (all) | 70 to 78F | Room temperature |
Key takeaways
- Keep most tarantulas at 70 to 78F room temperature with no heat lamp.
- Set humidity by species: arid 50 to 60 percent, tropical 70 to 80 percent.
- A tarantula on its back is molting, not dying, and must not be touched.
- Remove all live prey the moment you suspect pre-molt or a molt in progress.
- Wait 1 to 4 weeks after a molt for the fangs to harden before feeding.
Frequently asked questions
- My tarantula stopped eating, is it sick?
- Often not. A fast lasting days to weeks is one of the most common pre-molt signs, especially alongside a darkening abdomen or sealing into a burrow. Healthy tarantulas can also fast for long stretches between molts. Keep fresh water available, remove uneaten prey, and watch for the spider flipping onto its back, which confirms a molt.
- Should I mist my tarantula's enclosure?
- Usually only for tropical species, and even then sparingly. Many keepers raise humidity by dampening a corner of the substrate and keeping a full water dish, rather than misting, because heavy misting promotes mold and stresses the spider. Arid species should stay dry with just a water dish. Always match your approach to the species' natural climate.
- Why is my tarantula lying on its back?
- It is molting. Lying on the back or side is normal molting posture, not a sign of death, and flipping the spider over can injure or kill it. Leave it completely alone, remove any live prey at once, and do not feed or handle it until the new exoskeleton has hardened over the following days to weeks.
- How often do tarantulas molt?
- Spiderlings molt frequently, sometimes every few weeks to months as they grow fast, while mature adults may molt only once or twice a year. Molt frequency slows with age and depends on species, feeding and temperature. Logging each molt helps you predict the next one and recognize an unusually long gap worth watching.
Exotic Pet Husbandry Research, BigBalli. We translate invertebrate care into daily, trackable numbers, cross-checked against sources including the American Museum of Natural History and the RSPCA.
Crittora provides husbandry and educational information, not veterinary diagnosis or treatment. A failed molt, persistent fluid loss, or injury should be evaluated by a vet experienced with invertebrates.