Robert L. Brown

This paper presents an annotated inventory of the alien social wasps (Hymenoptera: Vespidae: Polistinae, Vespinae) of the South Pacific Oceanic islands, excluding Australia and Papua New Guinea. Here we include information on invasive social wasp distribution, known introductions and establishment dates, and notes on their invasive ecology. Introduced social wasps in the South Pacific consist of 11 species belonging to the Polistinae ( Polistes : n = 7) and Vespinae ( Dolichovespula : n = 1; Vespa : n = 1; Vespula : n = 2), nine of which are known to have established across the Pacific. Introduced species were recorded in nine countries and territories (Cook Islands, Easter Island, French Polynesia, Fiji, New Caledonia, New Zealand, Niue, Samoa, and Tonga), with the earliest records having happened between the 19 ^th century and the present day. We also provide novel commentary on the ongoing and recently detected incursion of Vespa velutina (an established and impactful invasive species in Europe) into New Zealand. This inventory provides a resource to further understand the invasion biology of social insects and to scaffold risk modelling and management efforts for a taxon of impactful invasive predators in a severely understudied area.

Aculeate wasps are apex predators and play an important role in regulating arthropod populations. Determining what they hunt and how their diet varies with species ecology, geography and demography is essential to value their contributions as pest controllers in natural and human-modified ecosystems. There are many practical advantages in the study of social wasp diets. As central place foragers, hundreds of foragers bring prey back to the same location (the nest) every day; this means wasp diets can be explored by identifying taxa in prey balls collected directly from foragers arriving at the nest. A second advantage is that the colonies tend to contain large numbers of brood: prey can be identified from the gut contents of larvae or from the faeces that remain after metamorphosis. Morphological identification of insect remnants found in prey balls has provided insights into wasp diets but this approach is time-consuming and requires expert taxonomists. Metabarcoding is a more efficient method for describing insect diets; it has been used to identify prey of social wasps by sequencing prey balls, larvae guts and larval faeces. However, because of the ecological impact, data on social wasp diets are currently heavily skewed towards invasive populations. We lack comprehensive studies documenting what social wasps hunt in their native habitats. We use DNA metabarcoding to analyse the prey in over 500 wasp larvae guts from 14 nests of Vespula spp, sampled in their native range, across southern England. We describe the diverse diets of these insects, with the detection of 12 arthropod Orders in the guts of 554 larvae, and explore how diet varies across different locations. These data demonstrate the highly generalist predator role provided by Vespula , highlighting the key ecological roles they play as regulators of a broad range of arthropod taxa in native ecosystems and provide an important baseline for further exploring their ecological and economic value.

Insects are the most diverse group on earth, providing a vast array of essential functions for people and nature. Yet, our appreciation of their contributions is biased towards a few economically important taxa, especially pollinating insects like honeybees. Other taxa are less well appreciated despite the important roles they play, and these taxa are rarely (if ever) the focus of conservation initiatives. Here, we explore the role that scientists play through their interactions with the media in shaping our attitudes towards one of the least appreciated insects—the aculeate (stinging) wasps. Vespine wasps are an excellent taxonomic group for such a study as they are important predators in native ecosystems (e.g., the Northern Hemisphere—in Europe and North America) but ecologically devastating as invasive species in many regions of the Southern Hemisphere (e.g., New Zealand, Australia, South America). Despite this, global media coverage of wasps invariably focuses on and emotively exaggerates the negative defensive stinging behaviour of wasps, and almost entirely overlooks their beneficial positive roles (as pest controllers and pollinators). Wasp and bee scientists from around the world were surveyed about their interactions with the media and how they considered these interactions to influence public perceptions and insect conservation. Our surveys capture the negative-wasp and positive-bee biases experienced by scientists through their interactions with the media. We consider the implications of such biases on wasp populations, their conservation and management, and make recommendations for a more balanced portrayal of this important and diverse group of insects.

The common and the German wasp, Vespula vulgaris and V. germanica, have proved to be prolific invasive species capable of degrading local ecosystems and costing invaded countries millions of dollars annually. Despite clear incentive, control strategies are yet to have any significant deleterious impact on invasive populations. Several species of arthropods are known to inhabit Vespula nests and feed upon developing larvae as either parasitoids or predators. Recent control strategies propose the use of such parasitoids as agents of biocontrol against invasive wasps (Volucella inanis in particular). Despite a general understanding of parasitoid ecology, some aspects such as prevalence, distribution, and behaviour remain limited. Here, we surveyed natural enemy prevalence in wasp nests over the period of three years and we tested larvae prey preference of two Volucella species, V. inanis and V. zonaria towards Vespula wasps. We find V. inanis to be the most prevalent of four prominent candidates for Vespid biocontrol—V. inanis, V. zonaria, Sphecophaga vesparum, and Metoecus paradoxus. Using two-choice assays, we find larvae of V. inanis to have slight yet significant prey preference for V. vulgaris larvae over V. germanica larvae, whilst V. zonaria display no preference. Furthermore, V. inanis were not averse to still predating upon V. germanica, doing so in 41% of trials. Prior exposure has no effect on the prey-preference. Our work provides experimental evidence that V. inanis is a promising candidate for biocontrol of invasive Vespula wasps, as the larvae predate on both target species of Vespula and display no exclusive preference among them.

Sphecophaga vesparum often parasitizes nests of vespid wasps such as Vespula vulgaris and Vespula germanica. Inside the colonies, the ectoparasitic larvae feed on the immature forms of the wasps. There are two adult forms of S. vesparum. The large, winged adults emerge from either rigid yellow cocoons or the orange cocoons used for overwintering. The small, brachypterous females emerge from soft, white cocoons. The species is facultative deuterotokous, producing mostly parthenogenic females and infrequently producing males. Here, we describe the production of chemical compounds related to the different developmental forms of the parasitoid S. vesparum (larvae, pupae and adults). We also compare the chemical profiles of the parasitoid wasp adults to those of their two main host species, Vespula vulgaris and Vespula germanica. The results show differences in hydrocarbon composition of larvae, pupae and adults of S. vesparum. Our results also suggest a partial mimicry of each of the two host species, mostly relating to linear alkanes present in both parasitoids and the host vespid wasp species. This matching is likely due to the recycling of the prey’s hydrocarbons, as has been found in other species of parasitoids.

Social wasps are a major pest in many countries around the world. Pathogens may influence wasp populations and could provide an option for population management via biological control. We investigated the pathology of nests of apparently healthy common wasps, Vespula vulgaris, with nests apparently suffering disease. First, next-generation sequencing and metatranscriptomic analysis were used to examine pathogen presence. The transcriptome of healthy and diseased V. vulgaris showed 27 known microbial phylotypes. Four of these were observed in diseased larvae alone (Aspergillus fumigatus, Moellerella wisconsensis, Moku virus, and the microsporidian Vavraia culicis). Kashmir Bee Virus (KBV) was found to be present in both healthy and diseased larvae. Moellerella wisconsensis is a human pathogen that was potentially misidentified in our wasps by the MEGAN analysis: it is more likely to be the related bacteria Hafnia alvei that is known to infect social insects. The closest identification to the putative pathogen identified as Vavraia culicis was likely to be another microsporidian Nosema vulgaris. PCR and subsequent Sanger sequencing using published or our own designed primers, confirmed the identity of Moellerella sp. (which may be Hafnia alvei), Aspergillus sp., KBV, Moku virus and Nosema. Secondly, we used an infection study by homogenising diseased wasp larvae and feeding them to entire nests of larvae in the laboratory. Three nests transinfected with diseased larvae all died within 19 days. No pathogen that we monitored, however, had a significantly higher prevalence in diseased than in healthy larvae. RT-qPCR analysis indicated that pathogen infections were significantly correlated, such as between KBV and Aspergillus sp. Social wasps clearly suffer from an array of pathogens, which may lead to the collapse of nests and larval death.

The ability of insects to associate olfactory cues with food from their environment has been well documented with various insect orders. However, these studies were based on prior training of insects to associate odors with food sources in the laboratory or in the field with almost no evidence for the development of this phenomenon in natural ecosystems. In New Zealand’s ancient Fuscospora spp. or beech forests, invasive Vespula social wasps were attracted to odor from honeydew (benzaldehyde and n-octanol) but did not respond to a known wasp attractant (isobutanol and acetic acid). On the other hand, wasps in a rural/suburban area in New Zealand did not respond to honeydew odor but responded instead to the known wasp attractant. Similarly, social wasps in Hungary did not respond to honeydew odor, but responded to the known wasp attractant. DNA sequences of Vespula vulgaris from the two locations in New Zealand were 100% identical. Similarly, DNA sequences of V. germanica from the two locations in New Zealand were 100% identical, indicating little or no intra-specific variation. On the other hand, DNA sequences of V. vulgaris and V. germanica from New Zealand were 99.56 and 99.78% matches with V. vulgaris and V. germanica samples from Hungary, respectively. Electroantennogram (EAG) response profiles of wasps from the three locations to benzaldehyde, isobutanol, acetic acid, n-octanol and heptyl butyrate were similar. The high similarity in DNA sequences and EAG profiles, with only a behavioral difference in the response to odor sources, suggests that social wasps in New Zealand’s beech forest have naturally developed associative learning for the odor of the carbohydrate-rich honeydew. This is the first study to provide conclusive evidence of the occurrence and the development of associative learning of food odor by social insects in a natural ecosystem free of human interference. The ability of social wasps to naturally develop associative learning of food odor might in part explain why they are extremely successful invaders of new ecosystems, especially those with rich honeydew resources. The finding of our study will have significant implications for the use of attractants in wasp monitoring and control in different habitats.