Diet of the wasps Vespula vulgaris and V. germanica in honeydew beech forest of the South Island, New Zealand

Abstract

Diets of Vespula vulgaris (L.) and V. germanica (F.) were sampled by intercepting returning foragers using an entrance trap. About 15% of returning foragers carried animal prey and 8% carried wood pulp. The remainder carried no external load; of those, 85% of V. vulgaris and 68% of V. germanica had a clear sugar liquid in their crops.

Vespula germanica foragers collected more Orthoptera and large Hymenoptera whereas V. vulgaris collected more Hemiptera and Lepidoptera. Temporal changes in the diet of both species were evident in 1990 but not in 1989.

Vespula germanica foragers return to colonies with a heavier prey load and larger volume of crop liquid than V. vulgaris. The weight of wood-pulp carried by foragers was similar for both species.

About 0.8 and 4.8 million prey loads per hectare per season entered nests in western and northern South Island honeydew beech forests, respectively. This represents a biomass of 1.4 and 8.1 kg/ha for western and northern sites. Carbohydrate intake, which is predominantly honeydew, was about 78 and 343 litres per hectare per season for western and northern sites, respectively.

Prey intake in the northern South Island was similar to that of the entire insectivorous bird fauna. Considerable dietary overlap between wasps and native insectivorous birds was identified.

This dietary overlap and the scale of consumption by wasps raises concern about the impact of these introduced insects on the native fauna.

Keywords:

• Vespula vulgaris
• V. germanica
• wasps
• diet
• prey consumption
• competition
• honeydew beech forest
• insectivorous birds
• biomass