Vespa velutina

Taxonomy

Order: Hymenoptera
Family: Vespidae
Subfamily: Vespinae
Genus: Vespa Linnaeus, 1758
Species: Vespa velutina Lepeletier, 1836
Common names: yellow-legged hornet, Asian hornet, Asian predatory wasp

Common name

yellow-legged hornet

Background

Vespa velutina is a hornet native to Asia but invasive in Europe. It is a generalist predator of medium- to large-sized insects and will also scavenge vertebrate carrion. It can have significant impacts on flies and social Hymenoptera, such as honey bees. This invasive species threatens honey production and native pollinators. It may be introduced and transported accidentally with soil associated with plants, garden furniture, pots, timber, vegetables, camping equipment, etc. Although Vespa velutina has not been intercepted in North America yet, it is believed to have high invasion potential.

How to separate from NGH

• This species is not present in North America, although its old common name, "Asian hornet," sometimes resulted in confusion with northern giant hornet
• Yellow-legged hornets are generally smaller; workers can be around half the size of a NGH, and queens can be around ¾ the size
• The legs are partially or mostly yellow, hence the common name "yellow-legged hornet"
• Body and head coloration can vary; most of the specimens shown here are form "nigrithorax," which is a darker form that is common in Europe

Distribution

Vespa velutina is widespread in Asia, occurring from northeastern India to Taiwan and as far south as Indonesia (Archer 1994). This species is now established in France and has been found throughout western Europe, including the United Kingdom, the Channel and Balearic Islands, Germany, and Ireland (Monceau et al. 2014).

Distribution map of Vespa velutina by GBIF: https://www.gbif.org/species/1311477

Diagnostic characteristics

• Queens and males average 30 mm (1 in.) long and workers 20 mm (0.7 in.) long
• The body is dark brown to black, with face and mouthparts orange, except for a dark clypeus
• The antennae are brown dorsally and orange ventrally
• Metasomal terga brown, with thin yellow band on segment 1 and a thin orange band on segments 2 and 3
• Metasomal segment 4 orange, sometimes with median basal triangular black mark
• Metasomal segments 5 and 6 orange-brown
• Legs are brown, with yellow tarsi
• The wings are brown-tinted.

Diversity

The most recent taxonomic revision of the genus treats all subspecific names in the genus Vespa as synonyms, effectively changing them to informal names for regional color forms. There are 10 recognized color forms (Carpenter and Kojima 1997).

Host/prey associations

Vespa velutina hunts Apis cerana (the eastern honey bee) in its native range. However, Apis mellifera is preferred because it lacks the defensive behaviors seen in A. cerana (Tan et al. 2007). Vespa velutina also preys on a wide range of large-bodied insects, including dragonflies, flies, and Orthoptera.

Nesting and general behavior

After mating in the late fall, new queens find a safe place to hibernate. In the spring the overwintering mated queen emerges and first constructs a paper nest low to the ground. After several months, once there are sufficient workers, they may abandon this nest and build a new one higher in a tree.

Vespa velutina nests are ovoid, with the cell combs enclosed by a paper envelope. They can become enormous, with one queen producing an average of 6,000 workers over the course of an entire season, though rarely including that many at any one time. The colony is largest by mid- to late summer (usually averaging between 450–1700 workers in peak season), which leads to increased predation on honey bee colonies. This hornet’s nests are annual, with the workers and males dying at the end of the season.

Known invasives

Vespa velutina is invasive in western Europe, South Korea, and Japan. The main color form found in Europe is often referred to as form "nigrithorax," which has been treated as a subspecies in the past.