BRITISH WILDLIFE Volume 29 Number 2 December 2017 The Asian Yellow-legged Hornet · The Wash St Helena: Island of Endemics · Larger Water Beetles of Britain and Ireland What Does ‘Traditional’ Management Really Mean? BRITISH WILDLIFE THE MAGAZINE FOR THE MODERN NATURALIST Magazine office: British Wildlife, 1–6 The Stables, Ford Road, Totnes, TQ9 5LE, UK Telephone 01803 467166 e-mail [email protected] website www.britishwildlife.com Publisher Bernard Mercer, [email protected] Editorial Assistant Guy Freeman, [email protected] Business Manager Anneli Meeder, [email protected] Advertising [email protected] Subscriptions Department [email protected] The paper used for this magazine has been independently certified as coming from © British Wildlife, part of NHBS Ltd, 2017 well‑managed forests and other controlled ISSN 0958-0956 sources according to the rules of the Forest Stewardship Council. All rights reserved. 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Join as a Bat Conservation Trust family member and help to save our bats. oung www.bats.org.uk/join © is free to members of the Y The Young Batworker Batworkers’ Club, the junior wiTn gfa omf itlhye m Beamt bers. rust, and to BC Conservation T 0345 1300 228 | BatConservationTrust | _BCT_ ii British Wildlife December 2017 The Asian Yellow-legged Hornet: the implacable advance of a bee-killer The Asian Yellow-legged Hornet: the implacable advance of a bee-killer Karine Monceau and Denis Thiéry The Asian Yellow-legged Hornet nest that was discovered in Gloucestershire in 2016. National Bee Unit he Asian Yellow-legged Hornet Vespa north Devon. Both UK records resulted in the velutina, known also as the Asian Hornet, discovery of nests, which were subsequently Tis among the most harmful of all the destroyed. Sightings have been reported also invasive species listed by the European Union. A from the Channel Islands; the first in the British relatively recent arrival from China, it is of concern Isles was on Alderney in 2016, with several more chiefly because of its likely impact on the European nests discovered in the following summer on both Honeybee Apis mellifera. The newly arrived insect Guernsey and Jersey. was first spotted in Europe in 2004, near Agen, Ecological impact between Bordeaux and Toulouse, in south-west France. The European population’s starting point The hornet forms a large colony, founded by a appears to have been when a single female mated single queen, which begins laying its eggs in April with four males (Arca et al. 2015); it is striking and produces thousands of individuals each year. A that the enormous numbers now present – there huge amount of protein is required in order to feed are probably more than 50,000 nests in France the larvae during the colony’s growth, and this is alone – appear not to have suffered because of this obtained mainly from other arthropods, including genetic bottleneck. The insect rapidly colonised honeybees, the latter comprising one-third to several other countries, including Spain, where two-thirds of the hornet’s diet, depending on it has reached the island of Mallorca, Portugal, the environment (Villemant et al. 2011). Wild Italy, Germany and, more recently, Belgium and pollinators clearly must suffer, but we are sorely Switzerland. It was officially recorded in the lacking in reliable data. More research has been Netherlands for the first time in summer 2017. conducted on the highly predatory Asian Yellow- The first confirmed UK sighting occurred in 2016, legged Hornet’s effect on commercial apiaries, in Gloucestershire, with a second a year later in where workers hunt during the summer, typically December 2017 British Wildlife 79 The Asian Yellow-legged Hornet: the implacable advance of a bee-killer synchronously wobble their abdomens as a visual warning, a behaviour known as ‘shimmering’. European Honeybees cannot defend themselves as effectively against attacks by hornets; they do sometimes display the bee-carpet reaction, but their attempts at heat-balling are nowhere near so efficient as those of their Asian counterparts (Arca et al. 2014). The mere presence of Asian Yellow- legged Hornets is a significant source of stress to the bees, resulting in reduced foraging by workers from attacked hives, with obvious consequences for the survival of colonies over winter (Arca 2012) and, probably, reducing the ability of attacked bees to learn the scent of, and thus avoid, the predators Hornet larvae inside the nest. Karine Monceau (Wang et al. 2016). This stress may also interact with the negative effects of neonicotinoid pesticides, hovering, or ‘hawking’, near a hive entrance and further reducing a bee’s ability to avoid predators catching returning honeybees by hooking them (Tan et al. 2014). with their front legs (Monceau et al. 2013a). They The Asian hornet may, in addition, be a vector then cut the captured bodies into pieces, extracting of pathogens such as Israeli Acute Paralysis Virus, sugars by licking the haemolymph (a fluid which infects European Honeybees in China and in equivalent in most invertebrates to blood) before France (Blanchard et al. 2008; Yañez et al. 2012). discarding all but the thorax, which is carried back Finally, the Asian Yellow-legged Hornet is potentially and fed to the larvae in order to provide them with a direct competitor of the native European Hornet protein. In Asia, the insect preys largely on the Vespa crabro, the latter being a predator of many Asian Honeybee Apis cerana and on the European common farmland pests, although early studies have Honeybee, which has been introduced there (Ken yet to find clear evidence of the occurrence of such et al. 2005; Yang 2005). competition (Monceau et al. 2015b). Asian Honeybees (known also as Eastern Honey- Economic impact bees) defend their colonies from raiding hornets by deploying a so-called ‘bee-carpet’, in which Beekeeping has in the last few decades suffered large numbers mass at the entrance of a hive as a several crises, these caused by such factors as deterrent, or by ‘heat-balling’, whereby they engulf the use of pesticides, the Varroa Mite Varroa the predator, making its body temperature rise to a destructor, the parasitic microsporidian Nosema lethal level (Ken et al. 2005; Tan et al. 2007, 2010, apis (the pathogen responsible for the disease 2012, 2013). Massed honeybees also sometimes nosemosis), and agricultural change, all of which Asian Yellow-legged Hornet workers hawking outside a honeybee hive in France. Karine Monceau 80 British Wildlife December 2017 The Asian Yellow-legged Hornet: the implacable advance of a bee-killer Queen Queen Asian Yellow-legged Hornet Vespa velutina European Hornet Vespa crabro Queen Queen Worker Nest of Median Wasp Common Wasp Median Wasp Vespula vulgaris Dolichovespula media The Asian Yellow-legged Hornet is smaller and darker than the European Hornet, and the largely black abdomen, thorax, and top of head help to identify the Asian species.