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term "hornet" is often used to refer to many of the wasps that build large
papery nests. The most notable paper wasp is the baldfaced hornet, Dolichovespula
maculata, and several species of yellowjackets (Vespula sp.),
which are really wasps. In actuality the only true hornet found in the United
States is the European hornet,Vespa crabro
L.
Description
Baldfaced hornets may be best
described as large, black and white, heavy-bodied wasps about ¾" long. They
typically build exposed, mottled grey
nests in trees or shrubs. Occasionally, the wasps will build nests under
roof overhangs, in attics, crawlspaces and wall voids, or under decks or
porches. The nests are constructed of a paper-like martial formed from chewed
wood. The nests are often described as "football shaped", but they may exceed
a basketball in diameter.
Yellowjackets are house fly-sized wasps with distinct yellow and black markings
and a few hairs. They construct a similar type of paper
nest; however, it will be tan in color, much smaller in size compared
to the hornet nest, and is usually found in an underground cavity. Common
locations for nests are in lawns, particularly in sandy exposed areas, as
well as at the base of trees or shrubs. Occasionally, yellowjackets will
nest in attics or walls voids of houses or storage buildings.
Life History
An individual hornet or yellow
jacket queen begins building a nest alone in the spring. Once a queen has
produced enough workers to take over nest-building and foraging duties,
she remains inside producing more offspring. The workers expand the nest,
forage for food, feed the young and defend the nest. Like other predatory
wasps, their diet consists mainly of other insects such as flies and bees.
Bald-faced hornets will also feed on their yellowjacket relatives. They
continue to enlarge the nest until fall when there may be 300-400 hornet,
or 600-800 yellowjacket workers. Frequently, it is not until this time that
the nest is noticed, although it has been there for many weeks, already.
In the late summer, the colony produces reproductives which are insects
that will mate. The mated female reproductives will serve as the next generation
of queens in the following spring. The male's main purpose is mating and
they cannot sting. Nests are abandoned by wintertime and the future queens
seek shelter alone, in protected places under tree bark, in old stumps,
or sometimes attics. The current year's nests are not reused the following
spring.
Behavior
Yellowjackets, in particular,
may be late season pests around picnics, trash cans, and humming bird feeders
as they scavenge. The only way to control this situation is to locate and
destroy the nest, which is rarely possible. As an alternative, keep all
outdoor food and drinks covered, except while actually eating. (see Beekeeping
Insect Note #15, Reducing the Likelihood of Stings During Outdoor
Activities). Bee guards or a coating of petroleum based chest rub can
be used on hummingbird feeders where the insects land. Trash cans should
be kept covered or have a flap over the opening. Defensive behavior occurs
in response to nest defense. If the nest is not in the immediate vicinity
the likelihood of stings is greatly reduced.
Control
The first decision to make is
whether control is actually necessary. Two points to remember:
- In spite of their reputations,
hornets and yellowjackets are actually beneficial because they prey
on many insects that we consider to be pests. They also serve as food
for other bears, skunks, birds, and other insects.
- Unlike honey bees, hornet
and yellowjacket colonies die out each year.
If a hornet nest is built high
in a tree, you may choose to simply wait until the colony dies out in late
fall or early winter. The nest will slowly deteriorate from weather or from
attack by hungry birds. If a nest is located where people may be stung or
if you (or others) are hypersensitive to bee/wasp stings, then colony destruction
may be appropriate. Here are some points to consider as you decide how to
approach the problem:
- Control is best achieved
by applying a pesticide directly into the nest opening. This can be
done at anytime of the day, but near dusk, most of the wasps are more
likely to be inside the nest. You can use any of the aerosol "Wasp &
Hornet" sprays that propel insecticide in a stream about 10-12 feet.
Direct the spray into the nest opening and then move away from the area
in case any of the wasps emerge from the nest. You may need to be repeat
the treatment on the following evening.
- Long sleeved shirt and long
pants may be worn when spraying to make the applicator feel more at
ease.
- Do not hold a lit flashlight
or stand near car headlights or other lights. Emerging wasps may be
attracted in that direction and sting anyone nearby.
- Do not pour gasoline or
petroleum down a nest hole. This is extremely hazardous and environmentally
unsound.
If the nest is in a wall void
or other inaccessible area in your home, you may consider hiring a pest
control company to do the work for you. If the nest is in a wall, it may
be desireable to remove it if convenient after spraying to avoid attracting
carpet beetles that can invade the home and attack garments made wool, silk
or fur. Yellowjacket traps (commercial or otherwise) have not shown to be
of any value in reducing a yellowjacket problem. In trash disposal or recycling
areas, closed containers and the use of PDB (paradichlorobenzene) blocks
may help repel some insects.
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