Yellow dung fly females go to fresh cow pats to mate and lay eggs. The male flies pursue the females in mobs and are so aggressive the females risk death, dismemberment, or being drowned in bovine excrement. To keep mobs of males away from his mate, and elimanate the chance that his sperm will be wasted, the male remains in copulation longer than necessary. This plugs up the female. Males also guard females throughout egg laying process.Source: Judson, Olivia, 2002, "Dr. Tatiana's Sex Advice For All Creation"