2 RELATED BUTTERFLY SPECIES AVOID OVIPOSITION NEAR EACH OTHERS EGGS

Some butterfly species avoid egg-laying on plants which already bear conspecific eggs, and thus reduce food competition between their offspring. In two Pieris species the females produce in their accessory glands an oviposition-deterring pheromone (ODP), which is combined with the egg during oviposition. The ODP collected from eggs or accessory glands of P. brassicae inhibits oviposition by P. rapae and vice versa. The ODP of either species stimulates tarsal receptors in both species. The antennae of the two pierids respond to the volatiles of their own and each other's eggs. Thus the ODPs of the two species may reduce not only intraspecific, but also interspecific food competition between their larvae. © 1990 Birkhäuser Verlag.