some importance as pests of forest or shade trees; quite a number of other species 
may create problems when they occur in abundance in picnicking areas, camp- 
grounds, or other recreational areas. 
Family Vespidae 
Hornets, Yellowjackets, and Potter Wasps 
The family Vespidae contains the well-known stinging wasps, hornets, and 
yellowjackets. More than 360 species have been recorded in America north of 
Mexico, about one-third of which occur in the Eastern United States. Considered as 
a whole, these insects are not very important as forest pests since very few of them 
are capable of inflicting serious injury to trees. Adults of the family differ consider- 
ably in size and appearance, but all are distinguished by the very long discoidal cell 
in the forewings, and by their common habit of folding their wings longitudinally 
while at rest. Some of the more common species live in nests or colonies containing 
a few to several hundreds or thousands of individuals. A synoptic catalog of species 
occurring in America north of Mexico is available (697). 
Social species construct nests out of papery material consisting of wood or 
foliage chewed up and elaborated by the insect. Hornet nests contain several to 
many tiers of hexagonal cells enclosed in a papery envelope and are usually 
attached to the limbs of bushes or trees or to the eaves of buildings. They are 
roughly spherical and often quite large, measuring 75 mm or more in diameter. 
Yellowjackets also construct nests of papery material, but these are usually placed 
out of sight in the ground, in stumps, or under objects. An exit hole leads to the 
outside. Wasp nests usually consist of a single horizontal comb or layer of cells 
attached to a support by a slender stalk. They may be found in many places, such as 
under the eaves of roofs, under porches, in open sheds, and on bushes, shrubs, and 
trees. The adults of all members of the family feed commonly on nectar, ripe fruits, 
sap, and honeydew. The larvae feed on other insects provided by the adults. 
The European hornet, Vespa crabro germana Christ, an introduced species, has 
been recorded from Quebec and Massachusetts to Alabama and North Dakota. 
According to reports, hollow trees, hollow posts, sheds, barns, porches, and even 
attics are preferred as nesting sites. These nests occasionally become very large, 
reaching a length of 90 cm and a diameter of 50 cm. There are reports of damage to 
trees and shrubs by the adults (/077). They may girdle small twigs and gnaw holes 
in the bark of larger branches, possibly in search of nest-building materials and sap. 
Injuries have been reported to lilac, birch, ash, and buckeye. The adults possess a 
long stinger and a large poison sac. This species is capable of inflicting painful 
stings, but does not appear to be as likely to attack when disturbed as is the 
baldfaced hornet. 
The baldfaced hornet, Vespula maculata (L.), a well-known member of the 
family, is widely distributed in the United States and Canada. Adults are 12 to 19 
mm long, largely black with white markings on the face and thorax, and with the 
posterior third of the abdomen white. It commonly attaches its nests to the limbs of 
trees or bushes, also occasionally to the walls and windows of houses. These nests 
may reach a diameter of 38 cm and contain up to several hundred hornets each. 
Baldfaced hornets attack at once when their nests are disturbed, and are capable of 
inflicting extremely painful stings. 
Vespula arenaria (F.), the yellowjacket wasp, and V. maculifrons (Buysson) are 
two of the more common species of yellowjackets in the Eastern United States. The 
former also occurs throughout the remainder of the United States, in Canada, and 
Alaska north to the Arctic Circle. V. arenaria belongs to the group of aerial nesters 
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