Tegulum

Tegulum is a term used in zoological anatomy derived from the Latin tegulum, meaning a covering or basin. In arachnology, it denotes the main, often globe-shaped portion of the male spider’s pedipalp that forms the genital bulb and houses the sperm reservoir. The tegulum bears the openings for the sperm pathway and, in many species, the embolus—a slender intromittent structure—arises from the tegulum to deliver sperm to the female during mating. The bulb of the pedipalp may also include a subtegulum, a subsidiary chamber; the tegulum and subtegulum are separated by a suture or constriction and present a range of shapes used in species diagnosis. The morphology of the tegulum, including the presence and arrangement of apophyses and the embolus, is a key character in spider taxonomy and systematics.

In broader usage, the term tegulum is not widely employed outside spiders and, when encountered, tends to refer to a general covering or housing structure in various invertebrate anatomies. However, there is no consistent, widely adopted definition beyond its specialized use in arachnology. The word remains primarily associated with the anatomy of the male spider pedipalp and the distinctive structures linked to its reproductive function.

See also: pedipalp, embolus, subtegulum, spider taxonomy.