ABSTRACT Papilio alexanor Esper, [1800] is a threatened European butterfly species listed in Annex IV of the Habitats Directive and in Appendix II of the Bern Convention, being considered extremely vulnerable to climate change. According to some projections (e.g., Bambu, a scenario of moderate climate change), it would be expected to lose 63% of its European climatic niche by the year 2050 and 77% by 2080. The few remaining populations are expected to become concentrated in the Maritime Alps. In 2009 and 2010, we studied what is probably the densest P. alexanor population in the Italian part of this area. It occurs in a series of dry, xerothermic grasslands, also partially occupied by an abandoned limestone quarry, where the larval food plant is Ptychotis saxifraga (L.) Loret & Barrandon. Females lay eggs in July, choosing patches where the food plants are higher and more abundant. The habitat preference, conservation status and survival of the early instars larvae of P. alexanor have been investigated in...