In the female grasshopper Gomphocerus rufus mating elicits 'secondary defense' which makes remating impossible. The behavioral change is caused by the liquid white secretions, proteins of less than 90 kD, which are produced by the white tubuli of the male's accessory glands. Experimental injection of the white secretions directly into the spermathecal duct of receptive virgins provokes 'secondary defense' instantly whereas sperm transfer had no such effect. 'Secondary defense' is also released by eggs entering the oviducts and excerting pressure against the oviductal walls on their way to oviposition.