Courtship, copulation, and genital mechanics in Physocyclus globosus (Araneae, Pholcidae)

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Abstract
The pholcid spider Physocyclus globosus (Taczanowski, 1873) was observed and videotaped courting and copulating, and genital mechanics and movements were analyzed by serial sectioning of freeze-fixed pairs. Just prior to copulation, the chelicerae of the male engage an apophysis on the female's epigynum. During copulation the male vibrates his abdomen rhythmically and makes repeated, relatively stereotyped twisting and flexing movements with his pedipalps, which are inserted simultaneously but asymmetrically in the female. The palps squeeze the female in the area of her epigyneal plate. Copulation with non-virgin females results 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 masses result from copulations with virgin females. Sperm extrusion was not associated consistently with precedence of sperm from either the first or the second male. It is argued that the palpal movements, and perhaps most rhythmic genitalic movements, in spiders may best be interpreted as a result of sexual selection by means of cryptic female choice, and probably function to provide females with additional information 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 have massive muscles that are only used during copulation.