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In monandrous species, females have to manage their mating receptivity not only to gather an appropriate sperm supply, but to avoid further male sexual harassment as well. The shutdown of female receptivity to mating is often an irreversible process and therefore should result from a reliable signal. Females of the red mason bee, Osmia bicornis (syn. O. rufa), mate only once within the first day after their emergence from the maternal nest. The unreceptivity to mating of a mated female is induced by a male post-copulatory display, which takes place for about 10 min after ejaculating. During this display the male obviously applies an anti-aphrodisiac that reduces female’s attractiveness resulting in protection from other rival male sexual harassment. Protection by odour is only temporarily needed because females eventually reduce their attractiveness and receptivity to mating by themselves within a few days after emergence. The autonomous decrease in virgin female’s receptivity to mating is simply age driven and independent from mating status. In summary, the involvement of ejaculate substances in causing a loss of female receptivity to mating can be excluded for this species.

Abstract. Desert locusts, Schistocerca gregaria (Forska˚l) (Orthoptera: Acrididae), exhibit a population density-dependent phase polymorphism which includes the gradual change of many morphological, physiological and behavioural characteristics. Many volatiles associated with desert locusts have been identified recently and it is assumed that they are involved in pheromonal control of behaviour and development of locusts. Ovipositing females deposit with their egg pods several volatiles that appear to be attractive to other females resulting -possibly in combination with environmental factors -in an aggregated oviposition. Mature males release several volatiles, among them phenylacetonitrile, which are reported to accelerate sexual maturation in young males. Also, aggregation pheromone systems for hoppers and adults have been described. However, recent studies and publications shed a new light on the postulated effects of some of these volatiles. Gregarious behaviour can undoubtedly be induced by mechanical stimuli. Furthermore, the main component of the adult aggregation pheromone system, phenylacetonitrile, is found to be a repellent obviously not involved in aggregation. Comprehensive studies have demonstrated that phenylacetonitrile is used by mature gregarious males as a courtship inhibition pheromone to enhance mate guarding. Recent progress, contradictory results and perspectives in desert locust pheromone research related to reproduction are summarized and discussed in this paper.