A medium-sized hornet; queens can be very big. Workers generally 18 to 25mm, queens to 35 mm. Marked with yellow and reddish-brown. Distinctive pattern on abdomen, as seen in the photos. There are several subspecies or geographical variants.
This species is widely distributed across Europe and parts of North China, Korea and Japan. In addition, it has also been accidentally introduced to parts of the USA and Canada.
Vespa crabro is probably the best known hornet; it is THE hornet described in most natural history guidebooks available worldwide. It is considered a very large wasp, but this is only in comparison with the usually small Vespula species (yellowjackets). As a hornet, it is only medium-sized, workers being slightly smaller than Vespa tropica, although the queens are indeed big.
The typical nest site of Vespa crabro is in an above-ground cavity such as a tree hollow. However, due to reduced natural habitat, the hornets are moving closer to urban environments, and often nest under roofs and inside sheds and barns. From photos I have seen, the nest envelope is tubular-imbricate, with lengthwise overlapping layers forming a “banded” pattern. The nest can get very large.
Photos of a Vespa crabro nest in Belgium. The larvae and pupal cell caps can be clearly seen, and the large wasp at the bottom is the queen. Photo copyright and courtesy of Jean-Luc Renneson.
Photo below copyright and courtesy of Christophe Barthelemy. A Vespa crabro nest in a tree hollow; photo taken in France.
Having no first hand experience with this species (I have never seen a live specimen), I have no idea how defensive it is when compared with other hornets. Many sources claim that it is actually gentle, compared to some yellowjackets (Vespula sp.) which can indeed be extremely quick to attack. However, in Japan, this species is considered relatively defensive, in comparison with species such as Vespa analis. Recently, Vespa velutina has invaded France and is apparently spreading in range there. Vespa velutina is feared throughout much of its range in Asia (Indonesia, Malaysia, Taiwan and even Hong Kong); I have been on the receiving end of a ferocious attack by this species and can say that it is truly the most aggressive species I have personally observed. However, a report (in French) states that while Vespa velutina is a potential pest due to its predation on honeybees, it is not particularly aggressive, being even less aggressive than Vespa crabro! Therefore, I believe that the "gentle giant" European hornet is in fact more aggressive than most of the Asian species! And several people I have talked to can attest to the fact that they are quite quick to attack, sometimes not tolerating anything within 6 feet of the nest.
This species is known on occasion to practice nest relocation. However, this is generally only when the nest grows too big to be contained in the initial nest site.