Indagini sul parassitismo in aree forestali ad alta densitaà diLymantria disparL.

Gypsy moth larvae and pupae were collected in 4 cork oak forest areas in the summer of 1931. Collection was made only in stations where more than 1000 egg clusters per 40 trees had been Registered. In one area (Tempio), the gypsy moth population was in the 2nd year of progradation; in another (Abbasanta), in the 1st year of culmination; and in two others (Ploaghe and Villanova), the 2nd year of culmination. Pathogenic agents, particularly polyhedral nuclear viruses, caused 60% to 70% mortality among the larvae of the three culmination phase populations but only 40% in the case of that in progradation. The tachinidsExorista larvarumL. andBlepharipa pratensisMeigen were responsable for a 30% parasitism, decreasing to 2% as pathogenic mortality increased. Among pupae, pathogenic mortality did not reach 10% in any of the areas, whereas parasitism rates reached nearly 90%. Mortality due to parasitism was between 73% and 88% among the two 2nd year culmination populations, and about 50% among the remaining two.B. pratensisandBrachymeria intermedia(Nees) were the most frequently recovered, confirming their importance in reducing gypsy moth populations. The tachinids (Exorista larvarumL. andE. segregataRond.) and ichneumonids (Theronia atalantaePoda andPimpla InstigatorF.), although more rarely observed, proved a useful indicator of gypsy moth gradatlon phases. As hosts,B. pratensisappeared to prefer female pupae, andB. intermediamales. The cases of multiparasitism and superparasitism observed are discussed.