Osservazioni sulla mirmecofauna e l'afidofauna della quercia da sughero in Sardegna

During the triennium 2010-2012, in some cork-oak stands of the north-eastern of Sardinia (Alà dei Sardi, OT), was conducted a survey on the pest status of some ant species associated with aphids living onQuercus suberLinnaeus. After a preliminary list of species occurring in the field, we studied the biology, behaviour, harmfulness and distribution of the population of the arboreal antLasius brunneusLatreille, the species proved to be the most directly harmful to the cork bark, and its trophobiontStomaphis quercusin cork oak forests in Sardinia. During their life cycle, the two trophobionts benefit from the protection provided by the cork bark. In particular, the aphid undergoes a monoic holocycle, spending much of the year inside the ant nest. Our investigations on the distribution of infested trees suggested that they are grouped into clusters, even though we occasionally found cork oaks (especially large ones) colonized by the formicid without any attacks on the surrounding trees. The ant also digs its nests in the female cork, damaging the production, and its infestations involved up to 20% of the cork oaks. The distribution of the two species was limited to some cork oak forests in the central and north-eastern parts of Sardinia between 450 and 780 m a.s.l. where the climatic conditions are typical of the cold sub-zone ofLauretumtype II with summer drought, according to Pavari’s phytoclimatic classification.