Spider molting, or ecdysis, is a complex physiological process essential for the growth and development of spiders. As arthropods, spiders possess an exoskeleton — a hard, external covering made primarily of chitin — that provides support, protection, and attachment points for muscles and organs.

However, this exoskeleton is rigid and cannot expand, limiting the spider's growth. Therefore, spiders must periodically molt to shed their old exoskeleton and replace it with a larger one to accommodate their increasing size.

The molting process is initiated by hormonal changes within the spider's body. These hormones trigger the production of enzymes that degrade the inner layers of the old exoskeleton, softening it and creating a space between the old exoskeleton and the spider's body.

Once the old exoskeleton is sufficiently softened, the spider begins the physical process of shedding. It typically starts by arching its body backward and breaking open the old exoskeleton near the cephalothorax (the fused head and thorax region). The spider then uses its legs and pedipalps to push and wriggle out of the exoskeleton, starting from the front and gradually working its way toward the rear.

Once free from the old exoskeleton, the spider's body is pale, soft, and highly flexible. At this stage, the spider is known as a post-molt or teneral spider. It will usually seek a safe, sheltered location to rest while its new exoskeleton hardens and darkens, a process known as sclerotization.

The duration of the molting process can vary depending on the spider species, age, size, and environmental conditions. Larger spiders typically take longer to molt than smaller ones due to the greater surface area of their exoskeletons. Additionally, factors such as temperature, humidity, and food availability can influence the frequency and success of molting.