Beech honeydew: Seasonal variation and use by wasps, honey bees, and other insects

Abstract

Variation in the production of beech honeydew by the scale insect (Ultracoelostoma assimile), and in the density and abundance of insects feeding on it, was studied in a mixed beech (Nothofagus) forest near Nelson, New Zealand. Nearly all anal tubes were connected to a feeding instar of the scale insect and so were able to deliver drops of honeydew to feeding insects and birds. The number of anal tubes and drops was high in winter and spring and declined to a trough in late summer and autumn. Drop quality (size and sugar concentration) also reached a low in the late summer and autumn. It is suggested that consumption of drops by wasps (mainly common wasps, Vespula vulgaris, but also German wasps, V. germanica) caused the paucity of honeydew in late summer and autumn. Wasps probably also prevented feral honey bees (Apis mellifera) from gathering honeydew then. Wasps were by far the most abundant insect feeding on honeydew, peaking at an average of 58 wasps per m² of trunk of honeydew-infested tree in March. Wasp numbers declined markedly in April. Concern is expressed about the impact of introduced wasps on endemic insects, honeydew and insectfeeding birds inhabiting the honeydew beech forests.