Contrasting foraging related behaviours in two sympatric wasps (Vespula maculifrons and V. germanica)

ABSTRACT.

• 1 Using pinned freshly killed wasps (yellowjackets) to simulate feeding animals, it was found that V. germanica was socially facilitated, and concentrated its foraging activity on those feeders with the most pinned wasps (twenty). V. maculifrons foragers responded inversely, preferentially foraging at feeders with few or no pinned wasps.
• 2 Using hand-painted drawing pins (thumb tacks) as wasp models, similar results were found, indicating that visual, rather than olfactory, cues were responsible for the observed distribution.
• 3 Vespula maculifrons and V. germanica exhibit aggression while foraging at honey-baited feeders. Both species attack conspecifics at frequencies lower than would be expected under random encounter.

     

Overwintering colonies of German (Vespula germanica) and common wasps (Vespula vulgaris) (Hymenoptera: Vespidae) in New Zealand

Abstract

Nests of both common (Vespula vulgaris) and German wasps (V. germanica) sometimes overwinter in New Zealand. Three overwintering common wasp colonies were found in low-altitude honeydew beech forest; about 2% of the colonies initiated there in 1988 survived the winter. Wasp traffic rates from nests in Nelson city and a nation wide survey of wasp abundance, showed that more German wasp than common wasp workers were on the wing in winter and spring. German wasp colonies in Nelson city were more likely to overwinter than were common wasp colonies. Of the active German wasp colonies recorded in Nelson in January and February 1989, only two (4%) had previously overwintered, but these two nests accounted for 38% of all German wasp workers estimated to leave nests in the area. Had other overwintering colonies not been poisoned, overwintering colonies might have accounted for up to 11 % of nests and produced up to 64% of German wasp workers on the wing in January and February 1989.

Overwintering common wasp colonies did not produce queens or drones in their first year or second spring, but all 10 overwintering German wasp colonies examined produced sexuals at both times. German wasp queens produced in winter and spring may influence the number of colonies successfully initiated and affect the population dynamics of German wasps in New Zealand.     

Comparative characteristics of nests of Vespula germanica (F.) and Vespula vulgaris (L.) (Hymenoptera: Vespinae) from Christchurch City,New Zealand

Abstract

From July 1987 to June 1989, 141 nests and 365 nests, respectively, of the adventive social vespines the German wasp, Vespula germanica (F.), and the common wasp V. vulgaris (L.), from the City of Christchurch, New Zealand, were evaluated for seven major characteristics.

There were few, if any, differences in nest sites, and from spring to early summer in nest traffic, nest size, and numbers of combs. However, Getman wasps showed no preference for direction of nest entrances, while common wasp nests were more numerous in areas most exposed to the morning sun. Some Getman wasp nests survived the winter and began producing new worker cells by late June, but all common wasp nests died by June. Because common wasp nests have been reported surviving the winter in beech forest, which produces honey dew, and honey dew is not available in Christchurch City, common wasp nest survival over winter may be more dependent upon carbohydrates and/or prey dependent upon carbohydrates than the survival of German wasp nests. The presence of large, expanding wasp nests from early spring must impose localised predation pressures virtually unknown in the Northern Hemisphere where overwintering nests are rare. Wasp population dynamics, and impacts of wasps on fauna, are likely to vary between different geographical areas of New Zealand, but as targets for biological control, the two wasp species can generally be considered to be quite similar.     

Distribution of social wasps (Hymenoptera: Vespidae) in New Zealand in 1987

Abstract

More than 50 000 social wasps (Hymenoptera: Vespidae) were collected between March and August 1987 from throughout New Zealand. The most widespread species is the German wasp (Vespula germanica). The common wasp (V. vulgaris) has colonised about half the country and appears to be still spreading. It tends to appear in urban areas first, presumably because it is transported there with people and/or their belongings. The Asian paper wasp (Polistes chinensis) and Australian paper wasp (P. humilis), are confined to the northern half of the North Island, but the former species is spreading south.     

Foraging niche separation of social wasps in an invaded area: Implications for their management

Foraging niche separation may be a mechanism to promote coexistence of two competing species by concentrating intraspecific competition relative to interspecific competition. The present study investigated foraging behaviour and microhabitat use of two coexisting species of invasive social wasps, Vespula germanica and Vespula vulgaris, when foraging for two different food resources. Also, we tested the attractiveness of traps baited with a synthetic lure for those two species. We found that V. germanica wasps prefer to forage at ground level regardless of the resource, while V. vulgaris prefers protein resources at the shrubland level given a choice between a protein bait at ground or at shrubland level. However, when baited with the synthetic lure, the species caught was not affected by the height at which traps were placed. That is, in a no choice scenario, the traps were sufficiently attractive to lure both species of wasps to both microhabitats (ground and shrubland levels). Thus, our results support the existence of spatial niche differentiation at least in protein foraging and suggest that the synthetic lure evaluated could be used to trap both species of Vespula wasps present in Argentina. These results could help to improve management strategies of these social wasps in an invaded area.     

Local dynamics of worker activity of the invasive Vespula germanica and V. vulgaris (Hymenoptera: Vespidae) wasps in Argentina

1. The abundance of insects depends essentially on the reproductive success of individuals. In social insects, however, the abundance of sterile workers outside a nest depends on colony size but is also determined by ontogeny, nest demands, and local environmental factors. For invasive social wasps, the drivers of worker abundance are important because they determine the impact that these species have on the native systems, people, and their goods. 2. The aim of the present study was to understand the relative importance of endogenous and exogenous factors on the abundance of workers of populations of Vespula spp., by analysing 12 years of trap captures in NW Patagonia. This is the first attempt to model the activity levels of invasive Vespula spp. wasps over time in Argentina. 3. It was shown that between years, the worker activity of both vespids presents fluctuations, and that of V. germanica is determined by the spring mean temperatures. Within the flight season, V. germanica worker activity is affected by the relative abundance of workers in that year, whereas for V. vulgaris, activity it is affected by the relative abundance of both species that year. We found no relationship between individual weather variables and activity within a flight season for both wasps. 4. The patterns observed for Argentina are similar to those observed in all invaded temperate areas where Vespula spp. are established. This study provides useful information to understand the driving factors that affect Vespula spp. worker activity in Argentina. This could be a necessary step to develop plans to manage these invasive social insects.     

The potential distribution of German wasps (Vespula germanica) in Argentina

Abstract

In the early 1980s, the German wasp (Vespula germanica) arrived in Argentina and became established in northern Patagonia. We use an ecoclimatic computer‐based program (CLIMEX) to predict the potential spread of wasps to other areas of the country. The model suggests that much of Argentina does not appear to be very suitable for the species’ establishment. However, more suitable areas than those currently colonised by the wasp occur in the centre of the country. Based on CLIMEX results, we suggest that, if the wasps ever break through the barrier of unfavourable habitat that surrounds their current distribution, they will continue dispersing to those areas. Notwithstanding this, factors other than climate may explain why German wasps are firmly established in areas otherwise considered to be inhospitable for the species.     

Carbohydrate bait preferences of wasps (Vespula vulgaris and V. germanica) (Hymenoptera: Vespidae) in New Zealand

Abstract

Carbohydrates are both a source of food and a potential bait for control of common and German wasps. Carbohydrate preferences of wasps were determined in a series of paired trials by counting the number of wasps caught in traps baited with carbohydrate‐based baits versus a standard protein‐based bait. Factors influencing wasp attraction to carbohydrate‐based baits included bait type, season, weather, and location. A 30% sucrose solution was more attractive than honey, jams, gels, or dry (solid) sugars. The sucrose solution was more attractive in spring and autumn than in summer, probably because rainfall washed away natural carbohydrate supplies. There was a significant relationship between rainfall in the previous week and the proportion of wasps caught in traps baited with sucrose solution versus sardine cat‐food. A higher proportion of German wasps than common wasps was caught in sucrose‐baited traps. This may have been related to seasonal differences in abundance and/or behavioural differences between the two species. In some locations, more wasps were caught in traps baited with sucrose solution than in those baited with sardine cat‐food. The proportion of wasps caught in sucrose‐baited traps was higher in locations without beech scale honeydew than with beech scale honey‐dew. Proportionally more non‐target species (mainly honey bees) and fewer wasps were caught in traps baited with sucrose solution than in those baited with sardine cat‐food. All five bee repellents tested also repelled wasps. These results indicate the importance of determining the bait preferences of wasps (carbohydrate or protein) and the presence of non‐target species before attempting a poison‐baiting operation. They also emphasise the need for a wasp‐specific carbohydrate‐based bait.     

The spread of the social wasp,Vespula germanica,in Australia

Abstract

Between 1977 and 1989 the social wasp Vespula germanicacolonised mainland Australia and became established in New South Wales, Victoria, and South Australia. Accidental transport between towns is the main mechanism of spread. In many towns wasp nests have not been detected until they became widespread; therefore, eradication is difficult Successful eradication has, however, been achieved in many other towns.

Nesting places vary considerably among localities but relatively little among years at anyone locality. Peak wasp abundance occurs between January and April. Control of V. germanica nests costs Australia an estimated $600,000 (Aust. $) annually.     

Occurrence of the common wasp,Vespula vulgaris (L.) (Hymenoptera: Vespidae) in New Zealand

Abstract

After occurring sporadically in New Zealand since 1921, the common wasp, Vespula vulgaris (L.), was found in March and April 1983 to be established in Dunedin, where 6 nests were discovered. Subsequent examination of museum specimens showed that queens had been collected in Wellington in 1978, and nests by January 1982. Christchurch was invaded in early 1984, several workers were collected near Auckland in March and April 1984, and workers were reported at Nelson in March and May 1984. The Dunedin nests were up to 6 times the size of nests recorded from the Northern Hemisphere, and produced up to 23 times as many new queens. Workers, nest size, and nest productivity were sufficiently different from those reported in western North America to suggest that the New Zealand population originated elsewhere. Colour patterning of the head and pronotum readily separate New Zealand V. vulgaris from New Zealand V. germanica. The nest carton of V. vulgaris is brown; that of V. germanica is grey. Conditions in New Zealand appear to be favourable for V. vulgaris; it can be expected to spread and it may at times reach the high population levels experienced in Europe and the western United States.     

Long‐term spatial memory in Vespula germanica social wasps: the influence of past experience on foraging behavior

Social insects exhibit complex learning and memory mechanisms while foraging. Vespula germanica (Fab.) (Hymenoptera: Vespidae) is an invasive social wasp that frequently forages on undepleted food sources, making several flights between the resource and the nest. Previous studies have shown that during this relocating behavior, wasps learn to associate food with a certain site, and can recall this association 1 h later. In this work, we evaluated whether this wasp species is capable of retrieving an established association after 24 h. For this purpose, we trained free flying individuals to collect proteinaceous food from an experimental plate (feeder) located in an experimental array. A total of 150 individuals were allowed 2, 4, or 8 visits. After the training phase, the array was removed and set up again 24 h later, but this time a second baited plate was placed opposite to the first. After 24 h we recorded the rate of wasps that returned to the experimental area and those which collected food from the previously learned feeding station or the nonlearned one. During the testing phase, we observed that a low rate of wasps trained with 2 collecting visits returned to the experimental area (22%), whereas the rate of returning wasps trained with 4 or 8 collecting visits was higher (51% and 41%, respectively). Moreover, wasps trained with 8 feeding visits collected food from the previously learned feeding station at a higher rate than those that did from the nonlearned one. In contrast, wasps trained 2 or 4 times chose both feeding stations at a similar rate. Thus, significantly more wasps returned to the previously learned feeding station after 8 repeated foraging flights but not after only 2 or 4 visits. This is the first report that demonstrates the existence of long‐term spatial memory in V. germanica wasps.     

Distribution,dispersal and spread of the invasive social wasp (Vespula germanica) in Argentina

We studied the distribution and spread of the invasive social wasp Vespula germanica in Argentina, focusing on the contribution of queen dispersal to territorial expansion. Vespula germanica is native to Eurasia and has invaded several regions of the world, including Southern Argentina. Flight potential of field‐collected queens was measured using flight mills. Also, by means of an extensive survey we estimated the rate of spread by analysing the relationship between years since arrival and distance from the introduction locality. The mean distance flown by wasp queens in flight mills was 404.7 ± 140.8 m (mean ± SE, n = 59), while the rate of spread of V. germanica was estimated at 37.2 ± 2.1 km year^?1 (mean ± SE, n = 67), although faster towards the south. The observed spread rate of V. germanica wasps in Argentina confirms the invasive potential shown by several Hymenoptera species worldwide. Still, a stratified geographical expansion pattern does not match observed queen dispersal abilities, suggesting that human‐aided transport of hibernating queens is the central driver of the current distribution of these wasps. We suggest that despite several life‐history traits known for social insects that contribute to successful invasion, wasp spread must still rely strongly on human mediated pathways. This observation sheds light on those factors that are crucial for managing invasions of this and related pestiferous wasps.     

Odour-mediated foraging by yellowjacket wasps (Hymenoptera: Vespidae): predation on leks of pheromone-calling Mediterranean fruit fly males (Diptera: Tephritidae)

Predation is probably the most important male mortality factor in insect species with courtship displays that render males performing them conspicuous targets of predators. Sexually active Mediterranean fruit fly males, Ceratitis capitata (Wied.), aggregate in leks, where they participate in agonistic encounters and engage in visual, acoustic and pheromone-calling displays to attract receptive females. The objective of this study was to assess: a) whether sexually displaying C. capitata males in leks inside host and non-host foliage are subject to predation by the most prominent predators yellow-jacket wasps, Vespula germanica (F.), and if so, b) whether olfactory, visual or auditive stimuli are used by foraging wasps in locating male C. capitata prey. Studies were carried out in a citrus orchard and surroundings on the island of Chios, Greece. Observations were conducted using perforated containers hung within mulberry, fig or citrus foliage. Living C. capitata flies of different sex and either mature or immature were placed inside. Our results show that the yellowjacket wasps have learned to associate the presence of sexually active medfly males aggregated in leks with their prey's pheromone (kairomone). Foraging wasps, flying through the crowns of host trees, responded to the odour source of C. capitata male pheromone by approaching from downwind. Even inside dense citrus tree foliage, wasps keyed in on aggregations of pheromone-calling males using olfactory stimuli. Stimuli of visual and acoustic male signalling were only used at close range, after having followed the pheromone plume close to its source. Visual cues played a greater role in directing wasp foraging under more open and exposed host foliage conditions. Odour-based foraging of wasps inside host foliage in the mid-morning hours, when medfly male lekking activities peak, shifted gradually to a more visual-based host fruit patrolling in the afternoons to capture ovipositing and feeding medfly females. On ripe fruit, particularly fig, V. germanica visual prey hunting also included the capture of feeding medfly males, other feeding Diptera, as well as medfly larvae extracted from wasp-made perforations in the fruit.     

Competition for honeydew between two social wasps in South Island beech forests,New Zealand

Summary Honeydew is a sugary secretion of beech scale insects (Ultracoelostoma spp.). Two introduced species of wasps forage on the sugar droplets in New Zealand beech forests. We hypothesize that competition between them may explain whyVespula germanica has become locally extinct in beech (Nothofagus) forest invaded byV. vulgaris. Changes in behaviour of the two wasp species in response to changes in the honeydew resource were monitored. Foraging and rainfall separately and together reduced the honeydew standing crop. In response to the standing crop decreasing, more wasps were found on honeydew trees, they became less active, spent more time lapping the tree surface, and ingested drops of honeydew at a slower rate.V. vulgaris was more active, and obtained drops and energy at a higher rate thanV. germanica. These behavioural differences may lead to competitive advantages affecting queen size and possibly survival.     

Polymorphic microsatellite loci for eusocial wasps (Hymenoptera: Vespidae)

Hymenopterans are an important model for studying the evolution of cooperation in animal societies. Here, we characterize 19 microsatellite loci, isolated from the common wasp Vespula vulgaris, that can be used to study genetic variation in three genera (seven species) within the Vespidae. The number of alleles in V. vulgaris was moderate, varying from 2 to 14, with expected heterozygosity ranging between 0.04 and 0.93. Eleven loci amplified DNA in V. austriaca and Dolichovespula sylvestris, nine in V. germanica, eight in Vespa crabro and V. rufa, seven in D. media and only five loci could be used for D. norwegica.     

The influence of past experience on wasp choice related to foraging behavior

Memory has been little studied in social wasps. Vespula germanica （Fab.） （Hymenoptera： Vespidae） frequently revisits nondepleted food sources, making several trips between the resource and the nest. In this study, we analyzed this relocating behavior in order to evaluate whether this species is capable of remembering an established association after 1 h. To this end, we trained wasps to feed from a certain array. Then it was removed, setting it up again 1 h later, but this time 2 baited feeders were put in place, one at the original feeding site and the other opposite the first. We recorded the proportion of returning foragers, and their choice of feeder, after either 1 or 4 feeding trials. After 1 h, 78% of wasps trained with 4 feeding trials and 65% trained with 1, returned to the experimental area. Furthermore, during the testing phase, wasps trained with 4 feeding trials collected food from the previously learned feeder significantly more frequently than from the nonlearned one （P 〈 0.05）. In contrast, wasps that had been trained only once chose both feeders equally. Thus, memory retrieval could be observed 1 h after wasps had collected food on 4 consecutive occasions, but not after only 1. To our knowledge, this is the first study showing that V. germanica is capable of remembering an association 1 h after the last associative event, demonstrating that 1 h does not impair memory retention if4 feeding experiences have occurred.     

<Emphasis Type="Italic">Vespula germanica</Emphasis> Foragers Do Not Scent-Mark Carbohydrate Food Sites

We tested whether foragers of Vespula germanica leave a chemical attractant at a carbohydrate food site. Foragers were allowed to make 50 or 100 visits to a feeder filled with a rich, unscented fructose solution. We then gave them a choice between this and an identical but unvisited feeder. There was no difference between the number of individuals that chose the visited feeder and those that chose the unvisited one. Instead, wasps showed a tendency to choose a feeder based on its relative position on the feeding stand. We conclude that foragers of V. germanica do not scent-mark food sites. Instead, in the absence of food odor, they rely on local visual cues to relocate carbohydrate food sources.     

A simulation model of biological control of social wasps (Vespinae) using mermithid nematodes

Abstract

The nematode (Pheromermis spp.) is a potential biocontrol agent for wasps (Vespula spp.) in countries where invasive populations of wasps cause serious economic, social, and conservation problems. Using a simulation model previously developed for hornets, which belong to a genus with a similar biology to Vespula, we investigated the possibility of using nematodes as a biological control agent. The model wasp colony was exposed to different simulated levels of nematode infection during colony development, and the final number of wasp sexuals produced recorded. The model predicted that early and high levels of wasp infection had the greatest effect on reducing sexual production. However, even colonies with high (80%) levels of infection were still able to produce some sexuals, indicating that wasp colonies are resilient to infections. The model identified several key areas needing further research, including the effects of nematodes on the behaviour and physiology of wasps, of lengthening the infective period, and of increasing infection levels in both the wasps and intermediate transport hosts.     

The impact of an exotic social wasp (Vespula germanica) on the native arthropod community of north-west Patagonia, Argentina: an experimental study

Abstract 1. Biological invasions are usually thought to have a negative impact on native communities. However, data supporting this idea are often based on comparative studies between invaded and non‐invaded areas, and are spatially and temporally limited. 2. The present study experimentally assessed the impact of an exotic wasp, Vespula germanica, on the native arthropod community of north‐west Patagonia during 3 years in an area of 80 ha. Vespula germanica is an exotic social vespid that invaded north‐west Patagonia 20 years ago. It has been suggested that its populations affect native arthropods because of its broad diet and also because Patagonia lacks natural enemies and potential competitors for these wasps. 3. Using wasp‐specific toxic baits, V. germanica abundance was reduced in five sites of native woodlands during 3 consecutive years. The abundance, species richness, and composition of arthropods between non‐poisoned (control) and poisoned sites was then compared, both before and after the wasps were poisoned. 4. Wasp abundance represented 6% of the total arthropod catches in non‐poisoned sites and was reduced, on average, by 50% in the treated areas. The abundance, species richness, and composition of the arthropod community (305 species, 24 600 individuals) did not differ between control areas and areas where the abundance of V. germanica was reduced. Significant differences in response variables were found only before wasp poisoning had begun and were related to variations among sites. 5. These results suggest that V. germanica is not affecting the local arthropod assemblages, contradicting past work in other regions. The low relative abundance of wasps in Patagonia, when compared with other invaded regions, might explain the findings. 6. The present study provides further evidence for the importance of large‐scale experimental work with before/after comparisons to fully understand the impact of invaders on natural communities.     

Changes in abundance of Vespula germanica and V. vulgaris in England

1. Thirteen time series, varying from 17 to 27 years, of the abundance of Vespula germanica and V. vulgaris from lowland England are examined. The time series depend on either spring queens and workers taken in Malaise or suction traps, or collected colonies. 2. During the late 1970s and early 1980s, the abundance of V. germanica declined abruptly but that of V. vulgaris did not. 3. During the early 1980s, the 2‐year cycle of annual abundance of V. vulgaris changed to a nearly perfectly damped pattern of annual abundances. 4. The most likely factor causing these population changes was the increased use of pesticides acting directly by killing the wasps and indirectly by reducing their food resources. 5. The difference in response of the two species to increased pesticide use may be related to a difference in foraging ability.