The Asian hornet (Vespa velutina), also known as the yellow-legged hornet or Asian predatory wasp, is a species of hornet indigenous to Southeast Asia. It is of concern as an invasive species in some other countries.
Vespa velutina is slightly smaller than the European hornet. Typically, queens are 30 mm (1.2 in) in length, and males about 24 mm (0.95 in). Workers measure about 20 mm (0.80 in) in length. The species has distinctive yellow tarsi (legs). The thorax is a velvety brown or black with a brown abdomen. Each abdominal segment has a narrow posterior yellow border, except for the fourth segment, which is orange. The head is black and the face yellow. Regional forms vary sufficiently in color to cause difficulties in classification, and several subspecies have been variously identified and ultimately rejected; while a history of recognizing subspecies within many of the Vespa species exists, including V. velutina, the most recent taxonomic revision of the genus treats all subspecific names in the genus Vespa as synonyms, effectively relegating them to no more than informal names for regional color forms. The color form causing concern about its invasiveness in Europe has been referred to as V. v. nigrithorax, though this name no longer has any taxonomic standing.