The early phase of courting behavior in the male Swordtail consists largely of 2 types, nipping and arcing, both probably serving to identify the male and to test the receptivity of the female. On her part, the female may show posing or nipping, which serve to stimulate a lethargic male. There may well be other less obvious responses, as movements of caudal or ventral fins, that signal readiness on the part of the female. The male flexes his intromittent organ several times before actual copulation is attempted, which may serve to get the capsule of spermatozoa to the end of the organ. Eventually he makes a thrust, with the organ aimed at the female''s genital papilla. If the female responds by swimming forward, the thrust is repeated, and they progress across the tank in a coordinated series of thrusts and advances, called a courting run. The whole mating sequence is then made up of interstimulation and response; it is not a purely male activity, from which the female tries to escape. Mating in the Platy is roughly similar. The biggest difference is that the courting run is absent; the female Platy remains stationary during the male thrusts. In the Platy, only about 1 out of 200 thrusts resulted in lasting contacts, in which the male''s gonopod may have penetrated the female''s vent. Only one such contact out of 16 resulted in viable young. This lack of precision is common to both species.