one of a number of tubular appendages that, in spiders and some insects, exudes silk threads. In spiders the silk is used to make webs, and in insects to make cocoons. Spinnerets in insects and spiders are not homologous structures.
The function of both types of ampullate glands is to produce draglines (silk threads that some spiders release while walking) and attach the egg sac to the spinnerets, as is typical in wolf spiders (Townley & Tillinghast 2003).
Spiders in the Family Theraphosidae are distinguished from other spiders by the presence of two pair of booklungs; cheliceral fangs open paraxial; maxillae and labial cuspules present; distinct lobe on the anterior maxillae; two pairs of spinnerets; posterior lateral spinnerets are digitiform (finger-like); eight eyes in two close rectangular rows on a small anterior tubercle on the carapace; the legs and body are hirsute (hairy) and the tarsi (feet) are scopulated (padded) with retractable claw tufts (Raven, 1985).