THE INFLUENCE OF EXTRAFLORAL NECTARIES ON PARASITISM OF AN INSECT HERBIVORE

The extrafloral nectaries of many plants promote ant defense against i nsect herbivores. We examined the influence of extrafloral nectaries o n the levels of parasitism of a generalist insect herbivore, the gypsy moth (Lymantria dispar L.). Larvae and pupae of the moth were collect ed from trees with and without extrafloral nectaries growing in the sa me forests in South Korea and reared to evaluate parasitism. More para sitism occurred on plants with extrafloral nectaries in seven of the n ine season-long collections at the six sites and in four out of five c ollecting periods. Parasitism was higher on the four main genera of pl ants with extrafloral nectaries than on any of five main genera of pla nts without extrafloral nectaries. There was no difference in parasito id richness; nine species occurred in each group, eight of which were the same. There was a positive and almost significant correlation betw een the abundance of plants with extrafloral nectaries and the parasit ism of gypsy moth at the sites. Extrafloral nectaries may reduce herbi vory by inducing more parasitism of the insect herbivores that attack plants bearing the glands.