Cribellate

Cribellate refers to an organ found in some spiders. This organ is a spinning field located on the rear of the spider's abdomen, typically between the spinnerets. It is characterized by its sieve-like structure, hence the name "cribellum" which comes from the Latin word for sieve. The cribellum is covered in thousands of tiny spigulae, which are sharp, hair-like bristles.

Spiders possessing a cribellum are known as cribellate spiders. These spiders use their cribellum to produce a specialized type of silk. This silk is not sticky in the conventional sense but is instead extremely fine and woolly. When the spider draws this silk through the spigulae on its cribellum, the bristles comb and aerate the silk, creating a fluffy, powdery network. This ultra-fine silk is then often spread over the spider's web.

The sticky droplets typically found on orb-weaver webs are absent in the webs of many cribellate spiders. Instead, their webs rely on the physical entanglement of prey within the fine, woolly silk. This unique silk production method is an adaptation found in several spider families, including the Uloboridae and some members of the Dictynidae and Amaurobiidae families. The presence or absence of a cribellum is a significant taxonomic feature used in spider classification.