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Vespa velutina or Yellow-legged Hornet is an insect native of South-East Asia, naturally distributed between Southern China, India, Indochina and Indonesia. For the effect of the geographical isolation of the different populations and the climatic diversity, Vespa velutina has differentiated into 11 subspecies, but only the northernmost subspecies, Vespa velutina nigrithorax (du Buysson, 1905), was accidentally introduced from China to other parts of the world. The introduction areas are South Korea in 2003, Europe in 2004 and Japan in 2012.
The first report of the presence of Vespa velutina in Europe was in 2004 in France, near the city of Bordeaux. Probably the introduction was caused by a single queen transported by a cargo ship from the Chinese provinces of Zhejiang and Jiangsu. In the following years the species has spread rapidly in the French territory colonizing most of the nation and subsequently entered in Italy. The species arrived in Italy in 2012, when some adults were captured in Liguria; first nests were discovered in 2013 in Liguria and Piedmont regions.

 
 

Vespa velutina is characterized by a dark brown, almost black thorax. The first three abdominal segments are dark brown with a yellow or yellow-brown backside margin; the fourth segment is almost entirely yellow-brown, with a reddish-brown end of the abdomen. The legs are dark, except for the ends (tarsus) that are yellow, hence the common name yellow-legged hornet. The front part of the head is yellow-orange and antennae are black at the ends and brown on the bottom. The size of the workers ranges between 19-30 mm, with a wingspan of 37-50 mm.

It is possible to recognize Vespa velutina or yellow-legged hornet from the European hornet (Vespa crabro) thanks to the following characteristics:

  • Different abdominal designs
  • Different colors of the legs
  • Different colors of the head

The males of Vespa velutina can be recognized from workers or queens for the absence of the sting and bigger antennas. Workers and queens are very similar, although the queens are generally heavier; however, only the internal analysis of the reproductive organs allows their definitive distinction.

Vespa velutina or Yellow-legged hornet is native to India, Indochina, Indonesia and southern China, where the nigrithorax subspecies is present. In Europe, following its introduction into France near the city of Bordeaux, the species started to spread in many neighbouring countries. In France, the species has quickly colonized much of the country in few years. Then Vespa velutina entered the north of Spain in 2010 and quickly colonized the three provinces of the Basque territory and then reached Galicia; recently Vespa velutina passed the Pyrenees in Catalonia and reached Majorca Island. The species is also spreading in Portugal. A first colonization of Belgium appears not to have led to the formation of viable populations, while recently some nests were found in Germany and Great Britain. Other areas of introduction are South Korea where Vespa velutina is present since 2003 and Japan since 2012.

In Italy the first animals were captured in 2012 in Liguria, near the cities of Ventimiglia and Loano. In 2013 the first nests were discovered, five in western Liguria and two in the province of Cuneo in Piedmont.

In the following years the species increased quickly its range: the area occupied by the species in Liguria was approximately 205 km2 in 2013, it increased to 346 km2 in 2014 and reached 930 km2 in 2015, with an annual estimated linear expansion rate of about 18.3 km/year. The western part of Liguria, especially from Ventimiglia to Arma di Taggia, is colonized with a massive presence of colonial nests. However, nests have also been found up to Imperia and animals up to Alassio and Albenga, indicating a continued spread of the species.

Adults were found also in Piedmont near the towns of Vicoforte Mondov√¨, Borgo San Dalmazzo, Caraglio, Mondovi and Rivoli. A nest was discovered in Monasterolo Casotto too. However the observations of the species in Piedmont are occasional and it seems that the species has not yet settled there permanently. However, these reports do not rule out the possibility of colonization in the coming years. A recent observation of the species come from the municipality of Bergantino in Veneto region, several kilometers away from Liguria and Piedmont regions.