INTRODUCTION
This atypically large black-and-white yellowjacket gets its
common name of baldfaced form its largely black color but mostly
white face, and that of hornet because of its large size and
aerial nest. Baldfaced
hornets are found throughout the
United States
.
RECOGNITION
Adult workers about 5/8-3/4+” (15-20+mm) long; queens about
¾+” (20+ mm). Color black with white pattern on most of face,
as 2 angled stripes on thorax towards head and on last 3 abdominal
segments. Head with clypeus (upper lip) broadly truncate, slightly notched at apex. Hind wing without a jugal lobe (lobe on rear near body). Pronotum in lateral view almost triangular,
extending to tegula (structure at base of front wing) or nearly
so. Middle tibia with 2 apical spurs. Builds paper enclosed aerial nests, grey in
color.
SIMILAR
GROUPS
(1) other Dolichovespula spp. (Vespidae) with pale markings on 1st 3 abdominal segments, less than 5/8” (15mm) long. (2) Yellowjackets (Vespula spp.) with yellow
markings including on 1st 3 abdominal segments, usually
less than 5/8” (15 mm). (3)
European hornet (Vespa Crabro) with pale markings on 1st 3 abdominal segments, nest envelope brown.
BIOLOGY
Baldfaced hornets are social insects which live in aerial nests. The adults are represented by workers which are sterile
females, queens, and males which come from unfertilized eggs
and usually appear in the late summer. Only inseminated females overwinter and do so
in sheltered places. In
the spring, she uses chewed-up cellulose material to build a
paper carton nest of several dozen cells covered by a paper
envelope. One egg is
laid in each cell as it is constructed. The queen feeds the developing larvae arthropod protein
material and nectar. After
about 30 days, the first 5-7 workers emerge and shortly thereafter
take over all the work except for egg laying. The next will eventually consist of 3-5 rounded paper
combs which are open ventrally and attached one below another,
and are covered with a many-layered envelope. Nest size varies up to 3,500 cells in 5 combs but usually
consists of less than 2, 000 cells in 3-4 combs and contains
100-400 workers at its peak (range to 636 workers). Later in the season, larger reproductive cells are built
in which queens and males will be reared; males are often reared
in old worker cells. The colony is then entering the declining phase. The newly emerged queens and males leave the nest and
mate. Only inseminated
queens hibernate and survive the winter. The founding queen, the workers, and the males
all die.
HABITS
The overwintering queen selects the nest site. This can vary from shrubs or vines at ground level to
66 ft. (20m) or higher in trees. Nests may also be built on overhangs, utility
poles, houses, sheds, or other structures. Nearly all nests are constructed in exposed locations. At maturity, the nests can be quite impressive
with sizes of up to 14” (35cm) in diameter and over 24” (60+
cm) in length.
Often
nests located in vegetation are not discovered until the leaves
fall in the autumn. Nests are not reused the next season.
CONTROL
baldfaced hornets are beneficial insects by helping to control
many pest insect species. However,
if the nest is located close to the ground and near an occupied
structure or recreational area, then control is warranted.
During
the day locate the nest. Control
should be done at night when most of the baldfaced hornets are
in the nest. Only background lighting should be used and
a bee veil should be worn. Apply
an appropriately labeled aerosol through the entrance hole at
the bottom of the nest. For high nests a “bee pole” which allows application
of the aerosol from the ground or a sizeable distance away gives
added safety for the applicator. The nest should be removed, placed in a plastic garbage
bag, and discarded so that no emerging pupae can cause problems.
