Testing muzzle and ploy devices to reduce predation of bees by Asian hornets

Since its accidental introduction in 2004, the Asian yellow-legged hornet (Vespa velutina) has quickly spread in France. V. velutina specializes in the emblematic honeybee, Apis mellifera which are unable to protect their colonies efficiently against this fierce new predator. Here, we investigated whether two defence devices, a ploy and a muzzle, can protect bee colonies. Our results showed that neither device was able to reduce the number of hornets present in front of the hive or their predation efficiency (i.e. the number of captured bees). However, we found more flying bees and a smaller bee carpet in the presence of a muzzle, evidence that this very cheap method of protection can reduce the hornets’ impact on the activity of the bee colony and thus probably enabling its survival. We also showed that the number of agonistic interactions among V. velutina individuals increased with the number of hornets but without influencing the predation rate in our experimental conditions. The threat to honey bees is now well described, but the Asian yellow-legged hornet very likely has an impact on another insect species that has been the subject of far fewer studies: The native European hornet (Vespa cabro). Monitoring of several apiaries suggests that high densities of both V. velutina and V. crabro are exclusive and that the two species are engaged in an exploitative competition interaction. We are thus already in a position to underline the need for combined protection, as well as for further studies to better understand the ecology of V. velutina, to reduce the damage they cause.     

Competition between the native and the introduced hornets Vespa crabro and Vespa velutina: a comparison of potentially relevant life‐history traits

1. Invasive alien species are a major threat to biodiversity. In addition to predation and parasitism, native species might suffer from competition when invasive alien species occupy a similar ecological niche. 2. This study focused on the potential interspecific interaction between two hornets: the Asian yellow‐legged hornet, Vespa velutina, a high‐concern invasive alien species recently arrived in Europe; and the native European hornet, Vespa crabro. The two species share a similar ecological niche and V. velutina is rapidly expanding across Europe, which suggests that V. crabro might suffer from competition. 3. Under laboratory‐controlled conditions, two life‐history traits that might cause the two species to compete were investigated: (i) the ability of workers to find food sources and their flexibility in exploiting them (through individual food item choice tests and exploration assays); and (ii) the worker resistance to pathogens (through immune challenge tests). 4. The results show that trophic preference of both species highly overlaps, with a marked dietary preference for honeybees compared with other insect prey and non‐prey protein items. No differences were observed in the exploratory behaviour of both species. Finally, constitutive antibacterial activity was greater in workers of the native species than in workers of the invasive hornet. 5. This laboratory study provides a first assessment under controlled conditions of the factors affecting competition between workers of two hornet species and proposes a framework to assess, in wild contexts, the magnitude of the competition and the impact of the introduced V. velutina on the native V. crabro.     

Options for the biological and physical control of Vespa velutina nigrithorax (Hym.: Vespidae) in Europe: A review

Recently, the environmental economist J.M. Salles (Salles, 2016 ) declared that “the Asian hornet was likely to be the most threatening invader insect in France.” Thirteen years after the accidental introduction in France, the Asian hornet (Vespa velutina nigrithorax) has invaded most west European countries. Little has been done to date to limit its progression and its economic, ecological and social impact. Although it is illusory to try to eradicate this species, it is known that a targeted control would limit its threatening trend. Current V. velutina control in France is mainly based on (i) high scale volunteer trapping by citizens and (ii) volunteer spotting of the nest. Evaluation of trapping strategies developed so far to control V. velutina expansion has highlighted their failure and has demonstrated the need to optimize nest detection techniques and to investigate on new control strategies. This review describes most of the means aimed to control predation and expansion of V. velutina, whether they have been scientifically assessed or only tested on field with decent success. Published prospective control methods and biological control techniques are also presented.     

Relationship between the age of Vespa velutina workers and their defensive behaviour established from colonies maintained in the laboratory

As the structural bases of insect societies are essential to colony survival, nests must be protected from predation. Nest defence behaviours are among the most important roles assigned to worker members. However, in hornet societies, temporal polyethism (age-dependent division of labour among workers) is assumed to be weak. Few studies have investigated this phenomenon, probably because hornet nests are aggressively defended and dangerous to approach. In the present study, we propose a method for rearing nests of Vespa velutina, a species newly introduced into Europe. This method enables the handling of hornets, and thus the design of experiments. By marking all newly emerged hornets, we recorded aggressiveness in workers of different ages from three captive colonies. We observed that nest defence behaviour in V. velutina depends on the age of the workers. Nest defence appears to be mediated by the queen, probably through pheromones that promote nest organization. We also identified a previously unreported but important behaviour in V. velutina that workers are aggressive towards male hornets. This behaviour might be a strategy to avoid inbreeding. Collectively, our results provide new research perspectives for the management of social hymenopteran predators.     

Microsatellite loci for genetic research in the hornet Vespa mandarinia and related species

We developed 5 microsatelitte loci in the hornet Vespa mandarinia from RAPD fragments. The 5 loci showed 3–7 alleles in V. mandarinia and many were also polymorphic in the related species, V. ducalis, V. analis, Dolichovespula norvegicoides and Vespula schrenckii. These results suggested the loci will be useful for analyzing genetic structure of Vespinae, at both the colony and population levels.     

Temperature dependence of the electrical resistivity of social wasp cuticle: A comparative study

Resistance to electricity by social wasp cuticle is temperature dependent within the range of 1–40°C. This was measured on the species Vespa orientalis (the Oriental hornet), Vespa crabro (the European hornet) and the wasp Dolichovespula saxonica. The resistance at first decreases with increased temperature, reaching a nadir which differs according to species, and then rises again up to 40°C, the highest temperature tested. It is suggested that the cuticular changes in resistivity at different temperatures reflect the wasp's mechanism for detecting and regulating the temperature in their normal environment.     

First detection of <Emphasis Type="Italic">Vespa velutina nigrithorax</Emphasis> (Hymenoptera: Vespidae) in the Balearic Islands (Western Mediterranean): a challenging study case

The yellow-legged hornet, Vespa velutina nigrithorax is an Invasive Alien Species introduced into Europe in 2004, and is currently present in France, Italy, Spain, Portugal, Germany, and Belgium. It was also recently introduced in the United Kingdom and Switzerland. Here we present the first detection of V. velutina in the westernmost Mediterranean islands (Majorca, Balearic archipelago). In October 2015, a specimen of hornet, which was later identified as V. velutina, was sent to the laboratory of Zoology at the University of the Balearic Islands by a beekeeper from the locality of Sóller (northwest of Majorca). After the identification, and in coordination with the local authorities, an intensive survey was implemented in the area of first detection using sticky traps baited with protein and nest detection by directly observing the flight route of adult hornets from two or three feeding points. The first nest was detected on 30th October 2015 and was entirely removed. The next year, nine other nests were located from August to November 2016 in the same area and again, all of them were removed entirely. It is the first report on an island of destroying nests as a means of controlling the spread, a scenario very different to mainland Europe. All nests were detected in evergreen tree species (pines, holm oaks, and common cypress) in the “Serra de Tramuntana”, a mountain range located in the north-west of the island of Majorca (3667 km²), which is situated 176 km off the mainland. Considering the presumably early stage of the invasion of V. velutina in Majorca, the size of the island, and the confinement of the detection area, we consider that this species could be eradicated if resources and a specific program for eradication in Majorca are implemented in coordination with all involved partners.     

Influence of Illuminance and Forager Experience on Use of Orientation Cues in Social Wasps (Vespinae)

We tested the influence of illuminance and level of forager experience on nest orientation behavior of the social wasps Vespula vulgaris, Vespa crabro, and Dolichovespula saxonica in an artificial laboratory tunnel system. The number of wasps which oriented themselves chemically via a terrestrial trail or used visual orientation were determined at different illuminance levels for foragers which were naïve or experienced with the tunnel system. In V. vulgaris and D. saxonica, mainly the young and naïve foragers used the chemical trail for orientation in brightness. Experienced foragers used visual cues for nest orientation. In V. crabro, naïve and experienced foragers followed the chemical trail in a similar intensity. In darkness, when visual orientation was limited, the relative importance of the chemical trail increased dramatically in all species and all experience classes.     

Quantitative analysis of research topics and public concern on V. velutina as invasive species in Asian and European countries

We analyzed the research topics and public concern on Vespa velutina as an invasive species in Asian and European countries quantitatively though digitized texts such as scientometrics and conservation culturomics. We collected 126 scientific publications of V. velutina published during the last three decades, and 423 news articles on V. velutina in South Korea. In total, 22 countries have contributed to scientific research on V. velutina. Research topics were clearly classified to studies on taxonomy and invasion of V. velutina. In South Korea, people have recognized the ecological and health impact of V. velutina. Although scientific and public interest in V. velutina has increased since 2000, research topics may be narrow and information of news articles may be simple. To achieve the sustainable management of V. velutina, multilateral studies including environmental, social, and economic research on V. velutina are necessary.     

Distribution,spread, and impact of the invasive hornet Vespa velutina in South Korea

Hornets (Vespa spp) are top insect predators that can control pests, but their venomous stings and defensive behavior cause numerous human deaths throughout Asia. Hornets usually inhabit rural areas which reduces potential conflict with humans. In 2003, the invasive hornet, Vespa velutina, arrived in southern Korea (Yeongdo region) and became established. It is currently spreading northwards at a rate of 10–20 km per year. Despite originating in tropical/subtropical areas of Indo-China, its nesting biology and life cycle in South Korea are similar to those found throughout its native range, with mature colonies containing 1000–1200 adults. In 7 years, V. velutina has become the most abundant hornet species in Southern Korea by displacing native Vespa species such as V. simillima, which has a similar nesting biology. We also found a significant positive correlation between the abundance of V. velutina and the degree of urbanization, indicating that this invasive species was well adapted to urban environments. This was supported by our finding that 41% of emergency call-outs (119 Rescue Services) to deal with social wasps/hornet problems were due to V. velutina, which was twice as high as the number of calls about the next most abundant species. The rapid spread of V. velutina across southern Korea indicates that this species will continue to spread north-westward in the Korean peninsula and will become a major problem as more people and beekeepers come into contact with this aggressive invasive hornet.     

Vespa velutina nest distribution at a local scale: An 8‐year survey of the invasive honeybee predator

Vespa velutina is an invasive species that was observed for the first time in France and Europe in 2004, which rapidly threatened domestic honeybees with active predation. For the first time in this study, we analyzed the distribution of V. velutina nests at a local scale to understand the pattern of nesting, and in 8 years of monitoring, a total of 528 nests were surveyed. With the exception of 2 years, the nests of V. velutina were randomly distributed within the monitored area, which suggested that intraspecific competition for nesting sites and/or food was unlikely. When the data for all years were combined, an aggregated distribution of nests at the seafront in the vicinity of the oyster farm and sportfishing activities was observed. This distribution suggested that seafood, attractive to vespids, might provide a valuable alternative food source that favored colony development. We also tested the effect of spring queen trapping of V. velutina on the distribution of nests in 2014, which was the year with the greatest number of colonies within the area; the position of the traps did not influence the distribution of the nests. For the first time, this study showed that (i) intraspecific competition was unlikely to be a mechanism for population regulation, (ii) some areas were more likely favored for hornet nests, and (iii) spring queen wasp trapping was inefficient as a method to limit the distribution of the V. velutina population.     

Caste differentiation and seasonal changes in Vespa velutina (Hym.: Vespidae) colonies in its introduced range

Since its introduction in France 10 years ago, the yellow‐legged hornet, Vespa velutina, has rapidly spread to neighbouring countries (Spain, Portugal, Belgium, Italy and Germany). It showed efficient social traits facilitating its invasive success. Only scarce and incomplete natural history studies were known from its native distribution area. Studying the biology of this species in its invasive distribution range was thus a prerequisite to the implementation of efficient control methods in a near future. During a 3‐year field survey, we collected 77 nests to investigate several of the species' key colony characteristics. Our results enabled us to accurately quantify each of the castes and to better understand their synchronicity throughout the season. Our study showed that mature nests are able to produce up to 13 000 individuals and that the size of mature nests is correlated to the number of individuals produced. This correlation enables the inference of one characteristic from the other. Furthermore, each mature nest can produce up to several hundreds of potential founder queens, a crucial datum in the light of today's unregulated spring queen trapping control campaigns. In addition, nest dissections enabled to record the incidence of nest relocation for the first time in this species. Results are discussed with regards to what is known in other Vespidae species, with a focus on Vespula species that are known to be invasive in many other countries worldwide.     

Occurrence of Vespa velutina Lepeletier from Korea, and a revised key for Korean Vespa species (Hymenoptera: Vespidae)

This is the first report of occurrence of Vespa velutina Lepeletier from Korea. The diagnosis and taxonomic relationship between geographical subspecies is provided, with a revised key to complement the previous taxonomic information of Korean Vespa species. The ecological aspect of the species is also discussed.     

COMPARISON OF CHITIN STRUCTURES DERIVED FROM THREE COMMON WASP SPECIES (Vespa crabro LINNAEUS, 1758, Vespa orientalis LINNAEUS, 1771 and Vespula germanica (FABRICIUS, 1793))

There has been no study on the chitin structure of wasp species. Here, we selected the three most common wasp species belonging to the family Vespidae for chitin extraction and characterization. Chitin was isolated from each wasp species and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X‐ray diffractometry (XRD), elemental analysis (EA), and scanning electron microscopy (SEM). The chitin contents of Vespa crabro, Vespa orientalis, and Vespula germanica were 8.3, 6.4, and 11.9%, respectively. The crystalline index (CrI) values for the chitin extracted from each species were 69.88, 53.92, and 50%, respectively. The most important finding of the study is that although the same method was used to extract chitin from each of the three wasp species, the degree of acetylation was different: for V. crabro and V. orientalis it was 96.85 and 99.82% (the chitin was extremely pure), respectively, whereas that for V. germanica the chitin was 79.83%.     

A new role for antennation in paper wasps (Hymenoptera,Vespidae): antennal courtship and sex dimorphic glands in antennomeres

Summary. Males of Polistes dominulus perform antennal vibrations and grasping of female antennae during pre-copulatory and copulatory phases. Male antennation plays a relevant role in mating success. In several antennomeres of males of P. dominulus and Vespa crabro, a further species in which we observed male antennation, we found secretory cells of class 1 and 3 associated to the same release site. In P. dominulus, class 3 cells with ampulla-like reservoirs and class 1 cells release their secretion through hairless multiporous areas. In V. crabro, tyloid-like structures are associated with large apodemes. The as yet unidentified secretion of these glands may act as a contact or low-volatile sex pheromone during courtship behaviour.Received 4 December 2003; revised 16 August 2004; accepted 7 September 2004.     

Daily and Seasonal Extranidal Behaviour Variations in the Invasive Yellow-Legged Hornet, <Emphasis Type="Italic">Vespa velutina</Emphasis> Lepeletier (Hymenoptera: Vespidae)

In eusocial insect species, the nest represents the fundamental element of the colony. Extranidal activities (foraging, nest maintenance, defence) are fundamental for the development and the survival of the colony. Therefore, they may represent interesting targets to disrupt to limit their expansion in case of pest species such as Vespa velutina, an alien predator of domestic honeybees in Europe. An accurate knowledge of the pattern of activity of this pest’s colonies is therefore required. Due to the highly defensive nature of this hornet, a video monitoring was realized on two colonies during their growth from August to November. Three major behaviours were monitored: nest maintenance, patrolling on the nest and foraging flights. Although of different size and monitored during different years, the two colonies exhibited similar patterns of daily and seasonal variation. This work is a first step in the study of this pest especially in view of control program.     

Long-term stability of hornet cuticular hydrocarbons facilitates chemotaxonomy using museum specimens

Cuticular hydrocarbons are key compounds used for insect chemical communication and their species-specificity makes them of great utility to chemotaxonomists. However, very little is known about their long-term stability in relation to their use as reliable taxonomic tools. We compared the cuticular hydrocarbon profiles of fresh extracts from four hornet ( Vespa ) species with extracts from specimens that were frozen for 1 year and of those stored in insect display boxes for 20 years. Cuticular hydrocarbon profiles were qualitatively very stable, maintaining their species-specific profiles even after 20 years. The long-term stability of cuticular hydrocarbons in hymenopterans opens up the possibility of using museum collections for chemotaxonomy studies and helping with the delineation of species in difficult groups.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 732–737.     

Activity rhythm and action range of workers of the invasive hornet predator of honeybees Vespa velutina,measured by radio frequency identification tags

In social insects, the activity rhythm of foragers and their action range determinate the activity of the colony. In vespids, which are mostly predators, the foraging range of workers determines their maximum predation pressure round the nest. One of these species, Vespa velutina, a recently invasive species introduced into Europe, exerts a strong predation on honeybees at the hive. Therefore, the definition of its activity rhythm and spatial range of predation is of primary importance. Using radio frequency identification tags (RFID), two experiments were carried out to (a) determine their return ability (called homing) in releasing 318 individuals at different distance from their colony and (b) monitor their foraging activity rhythm and the duration of their flights based on 71 individuals followed 24 hr/24 during 2 months. The homing ability of V. velutina was evaluated to be up to 5,000 m and was not affected by the cardinal orientation of release point. The lag time to return to the nest increased with the distance of release. Most of the flight activity took place between 07:00 a.m. and 08:00 p.m., hornets doing principally short flights of less than an hour. Foraging range was thus estimated ca. 1,000 m around the nest. This study of V. velutina assisted by RFID tags provides for the first time a baseline for its potential foraging distance that increase our knowledge of this species to (a) refine more accurately models for risk assessment and (b) define security perimeter for early detection of predation on invasion front.     

Cell wall structure and composition in the comb built by hornets and wasps (Vespinae,hymenoptera)

Morphological, mineralogical, and chemical investigations were undertaken to determine the structure and composition of the cell walls of the comb in the nest of Vespa orientalis, Paravespula germanica, and Vespacrabro. Nests of V. orientalis were from three sites having different soil types, namely, Khamra soil, Gramosol soil, and organically rich soil from the city dump in Tel Aviv. Nests of P. germanica were from areas rich in organic matter, and those of V. crabro, shipped from Austria, were similarly comprised of organic matter. Structure and composition of cell walls in the three species differed; furthermore, grain size in the combs differed from that of particles in the surrounding soil.