Akre, R.D., A. Greene, J.F. MacDonald, P.J. Landholt, and H.G. Davis. (1981). Yellowjackets
of North America, North of Mexico. U.S. Department of Agriculture, Washington, D.C. Handbook
Vespa crabro (European hornet) was introduced into the New York area between 1840 and 1860 (Shaw and Weidhaas, 1956; van der Vecht, 1957). Originally Palearctic, its estimated distribution in North America is given in figure 3.2. On the basis of isolated reports, V. crabro now occurs along the eastern seaboard from New England south into northern Georgia and Alabama, and westward to the Mississippi River from Tennessee north into the Ohio Valley. Scattered northern populations probably exist from the Dakotas to southern Ontario and Quebec, and the wasp has been reported as far south as New Orleans.
Few biological studies have been made of this species since the works of Janet (1895, 1903); however, the distribution of V. crabro in Europe was given by Guiglia (1972), and some behavioral aspects of one subspecies were recently investigated in Japan by Matsuura (1969, 1970, 1971, 1973, 1974). Little information is available on this species in America, and much of the information presented here is taken from Spradbery (1973a).
In Europe, V. crabro typically builds its nests in hollow trees. Nests are also found in thatched roofs, barns, attics, hollow walls of houses, and abandoned beehives. Similar nest sites are used in North America (fig. 33), and Duncan (1939) even reported some subterranean nests.
Nests built in unprotected locations are covered with a thick, brown envelope composed chiefly of coarse, decayed wood fibers, and, therefore, very fragile. Brown envelope and carton distinguish the nests of V. crabro from the more common gray nests of D. maculata. The envelope of V. crabro nests is usually composed of elongated shells or tunnels, which are distinct from the scalloped tan envelopes of Vespula vulgaris or V. maculifrons. In addition, cell size of Vespa is several times larger. Nests in protected locations, such as hollow trees or between walls of houses, typically have only a rudimentary envelope at the top of the nest, with most of the combs exposed.
V. crabro nests are often large because of the large individual cells, but contain relatively few cells. A typical mature colony has a nest of 1,500 to 3,000 cells in six to nine combs; the lower two to four combs contain queen cells. A huge nest collected in northern Georgia had 33 combs (nearly one-third reproductive), containing 5,566 cells (fig. 33 j). V crabro colonies have a long seasonal cycle with eclosion of reproductives occurring from late August to November in eastern seaboard States. At its peak of development, a large colony consists of about 1,000 workers. Typical colonies, however, are more likely to have 200 to 400 workers at their peak.
Workers of V crabro are predacious on a variety of insects, capturing large species such as grasshoppers and other orthopterans, flies, honey bees, and yellowjackets. Since they are powerful, agile wasps, they probably forage farther for prey than the smaller yellowjackets. The queen of V. crabro is attended by a “royal court” of workers, which are highly attracted to her (Matsuura, 1968, 1974). Workers fly at night, and are attracted to lighted windows in homes. “Sometimes ten or more will beat themselves against a window causing people inside to panic thinking they are trying to break the glass and invade the house to attack them. The very loud buzzing and the force with which they ‘attack’ the window is impressive” (C.W. Rettenmeyer, Univ. Conn., personal commun.). In the autumn, V. crabro males are often attracted to lights as well; therefore, in addition to morphological differences, a number of behavioral differences exist between this true hornet and yellow- jackets.
Workers of V. crabro have been reported to girdle twigs and branches of numerous trees and shrubs, including lilac, birch, ash, horsechestnut, dogwood, dahlia, rhododendron, and boxwood (Hitchcock, 1970; Shaw and Weidhaas, 1956). Much of this girdling is probably done for sap and not for fiber collection as the workers are highly attracted to the girdled area, imbibe sap constantly, but usually do not carry fibers away. The plants are sometimes killed. This species is a pest of honey bees in apiaries in Japan and Europe (Matsuura and Sakagami, 1973; Spradbery, 1973a), but there are no reports of similar depredations to honey bees in America. V. crabro is primarily a forest species having few contacts with man and presenting a minimal stinging hazard.