What unique feature surrounds the egg sacs of the Brown Widow spider?

The unique feature that surrounds the egg sacs of the Brown Widow spider is spiky furs. This distinctive characteristic sets the Brown Widow apart from other spider species. The spiky appearance not only serves as a physical barrier, making the egg sac less appealing to potential predators but also helps in camouflaging it within its environment, providing an additional layer of protection for the developing eggs. The spines can also create an unpleasant tactile experience for any creature that attempts to disturb the sac, deterring them from doing so.

While other options like silk threads, hardened shells, and bright colors may describe attributes associated with other types of spider egg sacs or serve different protective purposes, they do not specifically define the defining feature of the Brown Widow spider's egg sac.