Molting is an essential part of a tarantula’s life cycle, it’s how they grow! When a tarantula starts to prepare for a molt, it goes into a state called premolt. When a tarantula is in premolt, it becomes sluggish and refuses food, and if the “skin” under the abdomen is visible from hair kicking, you will notice its abdomen will change to a much darker color. Premolt can last a few days for fast growing spiderlings to months for adults of slower growing species such as the Arizona Blonde Tarantula (Aphonopelma chalcodes).
Before the molt, a tarantula will lay down a molt mat, which is essentially a sheet of non-sticky silk that protects a tarantula during molting. When a tarantula is ready to molt, it flips upside down on the molt mat. Many beginner keepers see their tarantula upside down, and assume that it is stuck, so they flip it right side up. This could actually be fatal for the tarantula, causing it to get stuck in its molt, at which point there is not much you can do for it. After flipping over, the tarantula will slowly begin to push out of its old exoskeleton. This can take hours to accomplish and is very exhausting for the spider. The video shown was filmed over a course of around 6 or 7 hours.
After molting, a tarantula is very soft and completely defenseless. This is when a tarantula is at its most vulnerable state. It may take anywhere from one day to harden up for very tiny spiderlings to weeks for some of the largest species. The tarantula in the video, a Burgundy Goliath Birdeater Tarantula, took 2 weeks from the molt to when her fangs finally completely hardened. When a tarantula molts, it can also regrow stomach linings, hairs that have been kicked off, and even lost limbs!