Removal of genital plugs and insemination by males with normal and experimentally modified palps in Leucauge mariana (Araneae: Tetragnathidae)

Both males and females of the spider Leucauge mariana (Taczanowski 1881) contribute material to the plugs that often occlude the genital openings of females in the field. Males were sometimes unable to remove or penetrate these plugs, but overcame others using three different mechanical mechanisms: snag the plug and pull it off; break and penetrate through it; and break its adhesion to the epigynum by injecting material under it. They used their genitalia to accomplish these tasks, despite the fact that the genital bulb lacks muscles and innervation, thus limiting the male's ability to guide genital movements precisely. The effects of two male genital structures, the conductor tip and the conductor hook on sperm transfer and genital plug removal were tested by direct observations of their morphology and behavior, and by experimental removal of structures from one but not the other palp of the same male. Removal of the conductor tip reduced sperm transfer, while removal of both the hook and the conductor reduced plug removal. A preliminary characterization of palp movements and their sequences did not reveal any behavior that seemed especially designed for removing plugs, as opposed to inseminating the female.