A disturbing new video lets you watch as a Mexican red-kneed tarantula (Brachypelma smithi) literally crawls out of its skin.

The 40-second time-lapse from The Cincinnati Zoo & Botanical Garden captures the adult tarantula as it tosses and turns, spending seven long hours shedding its old exoskeleton.

The Mexican red-kneed tarantula is a docile spider that inhabits the desert and scrublands of Mexico. And, just like all other arthropods, the red-kneed tarantula must moult in order to grow.

Arthropods are covered in a hard and inflexible exterior, which means they can't expand within this casing. This means that before they can grow bigger, they have to grow a new skin.

While adult tarantulas usually moult about once a year, younger tarantulas going through more routine growth spurts moult at a higher rate. Scientists call this 'ecdysis', and it is an extremely important process.

Initially, there's nothing to see. The tarantula begins secreting a new skin while it is still encased in the old exoskeleton. Yet once the living tissue between the old and the new skin begins to disintegrate, the moulting process begins.

First, the tarantula squeezes its abdomen, pushing fluid into its head and upper body. This creates a pressure that pops the exoskeleton right off of the spider's head.

The tarantula then flops onto its back and begins kicking away the old skin, like taking off a particularly tight pair of jeans.

Once the spider manages to unwrap itself from the old shell, the new and softer skin begins to harden, usually within a few days. For this reason, the tarantula does most of its growing immediately after ditching its old skin.

Still, moulting isn't just about growth. The new skin also comes with a whole bunch of added perks.

The final product is free of any external parasites, and it comes with brand new sensory and protective hairs.

Plus, when they are moulting, tarantulas can also replace internal organs, and even regrow lost appendages.

All in a day's work.