R. J. Harris

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

AbstractDiets 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 pred...

Impacts of the weed Tradescantia fluminensis on insect communities in fragmented forests in New Zealand

Abstract The impact of the weed Tradescantia fluminensis on insect communities, as represented by Malaise-trapped beetles (Coleoptera) and fungus gnats (Diptera: Mycetophilidae s. l.), was studied in three forest fragments. Each fragment contained three plots with and without a dense weed cover. Data on vegetation and habitat variables were collected. Twinspan and Decorana analyses separated the plots by fragment for fungus gnat communities, and nearly so for the presence/absence of beetle species. The fungus gnat communities separated into plots with and without tradescantia at two sites, and there were fewer species of fungus gnats and beetles in tradescantia plots at the site with the simplest habitat structure. The richness of beetle and fungus gnat species was correlated with vascular plant richness. As tradescantia is known to prevent regeneration of many native plants, we predict a corresponding decline in invertebrate diversity and fragment complementarity where the weed is established.

Comparison of baits containing fipronil and sulfluramid for the control of Vespula wasps

Abstract Fipronil is a new insecticide being trialed in baits for control of introduced social wasps (Vespula spp.). The efficacy of fipronil was compared with sulfluramid (Finitron® wasp bait). In a laboratory bioassay, fipronil was faster acting and equally as toxic at concentrations over 1000 times lower than sulfluramid. Doses of 0.2 mg of fipronil active (0.2 g of bait when used at 0.1%) were sufficient to reduce colony activity by 90%. Trials in a 300‐ha site in beech forest used a single poison operation, without prefeeding, and bait stations in either a 50 × 50 m or 100 × 50 m grid. Use of fipronil reduced colony activity within the treated area by 99.7%, whereas sulfluramid had minimal effect on colony activity. Some foragers reinvaded the treated blocks after treatment with fipronil, but wasp densities remained below estimated ecological damage thresholds for vulnerable invertebrates in this habitat. Baiting in lines resulted in variable control of nearby colonies. Despite the low doses of fipronil needed to kill colonies, low bait attractiveness may limit the success of control operations using fipronil in some situations.

Invasion success of the wasp parasitoid Sphecophaga vesparum vesparum (Curtis) in New Zealand

Abstract The wasp parasitoid Sphecophaga vesparum vesparum has been released in many parts of New Zealand since 1987 as a biological control agent for German (Vespula germanica) and common ( V. vulgaris) wasps. We checked whether the parasitoid had established at 33 release sites. At 26 of these sites, we inspected enough nests (at least 20) to be more than 80% certain that we would have detected the parasitoid if at least 8.5% of the nests had been attacked. We suggest that the probability of 5. v. vesparum successfully invading a site is greatly increased when a large number of founders are released and there is a high density of wasp nests. The parasitoid has established in at least two sites, Pelorus Bridge (Marlborough) and Ashley Forest (Canterbury). S. v. vesparum has been established at Pelorus Bridge since 1988 and annually infests an average of 8.5% of nests within 2 km of the release site. The parasitism rate has increased since the parasitoid first established. Despite this increase, we did no...

Frequency of overwintered Vespula germanica (Hymenoptera: Vespidae) colonies in scrubland‐pasture habitat and their impact on prey

Abstract Overwintered Vespula germanica colonies make a major contribution to the total wasp population in some New Zealand habitats. All vespulid colonies found at two scrubland‐pasture sites near Hamilton, New Zealand, were monitored in three successive years to record the frequency of overwintering. Ten percent of V. germanica colonies overwintered but no V. vulgaris colonies did so. Prey collected by an overwintered V. germanica colony was sampled over 13 months by intercepting returning foragers. The most common prey recorded were arthropods of the orders Diptera, Araneae, and Lepidoptera. The proportions of different prey orders in the diet varied seasonally. In winter‐spring compared with summer—autumn, Diptera decreased while Lepidoptera and other orders increased. An estimated 125.6 kg of prey was carried into the two overwintered colonies for which traffic rate was measured, 29% of which was captured during winter—spring (June—November) when foragers from annual colonies are few or absent. Overw...

Possible pathogens of social wasps (Hymenoptera: Vespidae) and their potential as biological control agents.

Abstract No practical methods are currently available for area‐wide, long‐term control of social wasps in New Zealand. Pathogens have received little attention as potential control agents. Records from wasps of the genera Vespula, Vespa, and Dolicho‐vespula and their associated nest material include 50 fungal, 12 bacterial, 5–7 nematode, 4 protozoan, and 2 viral species, although few have been confirmed through bioassay as pathogens of these wasp species. Despite few naturally‐occurring host‐specific pathogens and records of diseased colonies, wasps are susceptible to generalist insect diseases in bioassays. Fungi belonging to the genera Aspergillus, Paecilomyces, Metarhizium, and Beauveria have been confirmed through bioassay as Vespiniae pathogens, as have the bacteria Serratia marcescens and Bacillus thuringiensis, and nematodes Heterorhabditis bacteriophora, Steinernema (= Neoaplectana) sp., S. feltiae, S. carpocapsae and Pheromermis vesparum. Several of the pathogens listed here provide a resource fr...

Variation in the quality of Vespula vulgaris (L.) queens (Hymenoptera: Vespidae) and its significance in wasp population dynamics

Abstract Density‐related variation in queen quality has been proposed as a possible mechanism regulating population fluctuations in Vespula species. We investigated annual variation in the quality (size, weight, and fat content) of adult V. vulgaris queens representing four stages of their life cycle (spring, founding, developing, and emerged) taken from six sites in beech forest, South Island, New Zealand. For each queen the dry weight, head width, and thorax length was measured. For a subsample of queens, the fat content was determined by ether extraction. The size of queen cells was measured from a subsample of nests. Size, weight, and fat content of queens varied between wasp colonies and sites. The smallest juvenile queens were under‐represented in the reproductive population. There was no direct link between body size and food supply. Size and weight of developing queens increased as the number of cells in the nest increased. The size of the queen cells varied significantly among layers in a nest an...

Aspergillus flavus as a pathogen of wasps, Vespula spp., in New Zealand

Abstract A fungus, identified as Aspergillus flavus (Deuteromycete: Hyphomycetes), was isolated from dead, field‐collected Vespula vulgaris larvae (Hymenoptera: Vespidae). After isolation and pure culturing, the fungus was inoculated onto field‐collected larvae of V. germanica and V. vulgaris. Disease symptoms developed in some larvae within 24 h, and eventual emergence among treated V. germanica larvae was only 0.8% compared to 52% in the untreated controls, and 1.3% compared to 40.9% for V. vulgaris. Although the fungus demonstrates the potential of inundative pathogens as control agents of social wasps, the production of human carcinogenic aflatoxins by most A. flavus strains is expected to restrain consideration of this fungus as a biological control agent.

No evidence for establishment of the wasp parasitoid, Sphecophaga vesparum burra (Cresson) (Hymenoptera: Ichneumonidae) at two sites in New Zealand.

Abstract Sphecophaga vesparum burra (Cresson) (Hymenoptera: Ichneumonidae) has been released at seven sites in New Zealand as a biological control agent for wasps (Vespula spp.). Between 1996 and 1998, more than 35 000 overwintering cocoons were released nationwide, more than half of them at two South Island sites: Binser Track in Arthurs Pass National Park (13 200 cocoons) and Tennyson Inlet in the Marlborough Sounds (13 660 cocoons). Monitoring at these two climatically and altitudinally disparate sites revealed that over 5000 adult parasitoids emerged at each site over the 4 years. More than 300 wasp nests were dug and inspected for attack by S. v. burra, but there was no evidence of establishment.

Confirmation of the establishment of three adventive ants (Hymenoptera: Formicidae) in New Zealand: Cardiocondyla minutior Forel, Ponera leae Forel, Mayriella abstinens Forel

The status of three adventive exotic ant species in New Zealand is discussed. Cardiocondyla minutior Forel is recorded for the first time, and is presumed to be established. Recent collections of Ponera leae Forel and Mayriella abstinens Forel confirm the establishment of these two species. Their establishment was, previously considered doubtful. Collection details and brief descriptions are given for each species.