calamistrum

Century Dictionary and Cyclopedia

1. n. One of the curved movable spines forming a double row on the upper surface of the sixth or penultimate joint of the posterior legs of certain spiders. The calamistra are used to curl and bind the lines of silk issuing from the spinnerets, forming a filmy web peculiar to the species possessing these organs.

Wiktionary

1. n. zoology A comb-like structure on the metatarsus of the hind legs of certain spiders (Ciniflonidae), used to curl certain fibres in the construction of their webs.

GNU Webster's 1913

1. n. (Zoöl.) A comblike structure on the metatarsus of the hind legs of certain spiders (Ciniflonidæ), used to curl certain fibers in the construction of their webs.