Wasp Numbers in Honeydew Beech Forest
At the peak of the wasp season wasps in honeydew beech forests have an average biomass of about 3.8 kg per hectare — 10 000 workers per hectare. These workers are actively foraging for food and between 50 and 65% of them collect honeydew.
Vespula wasps have successfully invaded beech (Nothofagus) forests in New Zealand. However, common wasps have displaced German wasps from honeydew beech forest. This may be because common wasps are more efficient at harvesting honeydew. Common wasps collect honeydew at a faster rate than German wasps, and spend less time lapping honeydew (which has often fermented) from the trunk when the standing crop of honeydew is low, so that fewer of them become lethargic and less effective feeders.
A Geographic Information System (GIS) was used to model the distribution of the scale insect as an estimation of the land area where honeydew is available as a resource — approximately 1 000 000 ha. The distribution of honeydew also approximates the extent of forest infested with high numbers of wasps. Wasps have been recorded in densities up to 370 wasps m-2 of tree trunk in honeydew beech forests. Workers are able to carry loads of about 15 microlitres of honeydew at a time.
Average nest density was about 11 nest per hectare in seven honeydew beech forest sites measured for 10 years. However, there is enormous spatial and temporal variation in abundance. Nest densities for 19 honeydew beech forest sites measured in 1989 ranged from 1 to 33 nests per hectare. Wasp nest density also varies from year to year, ranging between 8 and 34 wasp nests per hectare in 4 years at one site.
 |
Impact on birds |
 |
Impact on invertebrates |