Spinneret

Definition

A silk-spinning organ found in spiders (Araneae) and certain insects, typically consisting of one or more paired, segmented, tubular or conical projections through which liquid silk protein is extruded and drawn into solid filaments upon contact with air. In spiders, spinnerets are located on the ventral opisthosoma (abdomen) and usually comprise six (rarely two, four, or eight) movable structures that can operate independently or in concert to control thread diameter, orientation, and placement. In insects, spinnerets occur in larval Lepidoptera (caterpillars) as modified labial glands opening via a median spinneret or paired structures on the labium, and in adult Embioptera (webspinners) as enlarged, silk-producing basitarsi on the forelegs used to construct communal silk galleries.

Etymology

Example

Orb-weaving spiders (Araneidae) use their anterior lateral spinnerets to extrude the viscid capture spiral while the posterior median spinnerets produce the structural radii and frame threads of the web.

Synonyms

• silk gland outlet
• sericterium (in embryonic/lepidopteran contexts)

Related Terms

• silk
• spider
• caterpillar
• Embioptera
• opisthosoma
• Labium
• sericin
• fibroin
• cribellum
• spigot

Usage Notes

Number and arrangement of spinnerets are taxonomically significant: mygalomorph spiders typically retain four spinnerets, while most araneomorphs have six with the anterior pair often reduced or lost. The term is sometimes loosely applied to the entire silk-producing apparatus, but strictly refers to the external cuticular structures through which silk emerges. Contrast with 'spinner' (the organism) and 'spinneret' (the organ); avoid confusing with industrial textile machinery of the same name.