The effect of introduced wasp (Vespula vulgaris, Hymenoptera: Vespidae) predation on the dispersive life history stages of beech scale insects (Ultracoelostoma spp., Homoptera: Margarodidae)

Abstract

Introduced wasps reach huge densities in honeydew beech forests and have been found to substantially reduce the abundance of many species of invertebrates. However, the effects of wasps on the beech scale insect, which has been identified as a key species due to the large amounts of carbohydrate-rich honeydew it produces, have not been investigated. The aim of this study was to determine the effect of direct wasp predation on winged, adult male scale insects, whose flight period coincides with the peak wasp season. We found that wasps have no discernible effect on the persistence of male scale insects. Samples from malaise flight intercept traps inside and outside a wasp controlled area also showed that high densities of wasps had no effect on the activity-density of male scale insects or first instar crawlers. The peak in the male scale insect flight period was in mid February, two months later than the peak observed in a previous study of male beech scale insects, although the biotic or abiotic factors driving this variation are still unknown. The significance of these results is hard to quantify without some knowledge of the role that male scale insects play in the population dynamics of the beech scale insect, but it appears that introduced wasps do not significantly affect the life history or population density of beech scale insects.