hymenoptera

Although many species of native invertebrates have been identified on toxic baits containing sodium monofluoroacetate (1080) following aerial operations for possum control, few quantitative data are available to determine the risk of primacy or secondary poisoning that may result from these exposures. This paper reports on a series of studies conducted to determine the risk of 1080 exposure to one such non-target insect, the native ant Huberia striata. Subsequent risk of secondary poisoning to insectivorous animals is extrapolated.

The measurement of parasitism rates of wasp nests;lt Pelorus Bridge, New Zealand, at different distances from the initial release point suggests that the mean displacement of the parasitoid has increased by 1—1.5 km y(-1) from 1988 to 1993. Since average parasitism rates within this radius at any given site show little trend over time, this suggests an approximate 3-fold increase in the total parasitoid population each year, two-thirds of which is devoted to dispersal and one-third to maintaining local populations.

Introduced common wasps (Vespula vulgaris) are widespread, abundant pests in New Zealand. They compete for food with native birds and feed on native invertebrates. We poisoned wasps annually over 4 years to see if it was possible to reduce their abundance in two 30-ha beech forest sites. Two different poisons (sodium monofluoroacetate and sulfluramid) were used, mixed with sardine catfood. There was no evidence that one poison was more effective than the other.

Honeydew, the sugary exudate of the scale insect Ultracoelostoma brittini, is an important food source in black beech (Nothofagus solandri var. solandri) forests in the South Island of New Zealand. Two of the most prominent foragers of honeydew are honey bees (Apis mellifera) and wasps (Vespula germanica and V. vulgaris). Observations in the field and using a captive bee hive were used to investigate competition between bees and wasps feeding on honeydew.

Low acceptance of protein baits by common (Vespula vulgaris) and German (V. germanica) wasps (Hymenoptera: Vespidae) occurred after rain in honeydew beech forest. This corresponded with a sharp decrease in the proportion of natural protein in the diet of V. vulgaris and V. germanica, and a reduction in the concentration of carbohydrate-rich honeydew in the crops of foraging wasps carrying liquid.