COURTSHIP, COPULATION, AND GENITAL MECHANICS IN PHYSOCYCLUS-GLOBOSUS (ARANEAE, PHOLCIDAE)

The pholcid spider Physocyclus globosus (Taczanowski, 1873) was observ ed and videotaped courting and copulating, and genital mechanics and m ovements were analyzed by serial sectioning of freeze-fixed pairs. Jus t prior to copulation, the chelicerae of the male engage an apophysis on the female's epigynum. During copulation the male vibrates his abdo men rhythmically and makes repeated, relatively stereotyped twisting a nd flexing movements with his pedipalps, which are inserted simultaneo usly but asymmetrically in the female. The palps squeeze the female in the area of her epigyneal plate. Copulation with non-virgin females r esults in the extrusion of a mass of sperm from the female's genitalia during copulation or up to several minutes after it ends; no such mas ses result from copulations with virgin females. Sperm extrusion was n ot associated consistently with precedence of sperm from either the fi rst or the second male. It is argued that the palpal movements, and pe rhaps most rhythmic genitalic movements, in spiders may best be interp reted as a result of sexual selection by means of cryptic female choic e, and probably function to provide females with additional informatio n about the male. Pholcids in general, and some genera in particular ( including Physocyclus), may be unusual in that the vigour of males may play a significant role during copulatory courtship, as their palps h ave massive muscles that are only used during copulation.