Applegater., September 01, 2012, Page 13, Image 13

Applegater Fall 2012 13
Notes from a Rogue entomologist
The sting of summer:
Yellow jackets and paper wasps
bY RichARD j. hiLTOn
There is nothing like having a and white and build their nests above
large black and yellow insect buzz by ground, usually in shrubs. This is
at eye level to get one’s attention. I a large football-shaped nest with an
am not talking about a warm and entry hole at the bottom that is often
fuzzy bumblebee, but a cold and steely mistakenly depicted in children’s
yellow jacket, one of the banes of books as a honeybee hive. Paper wasps
summer. That combination of black are most familiar as the wasps that
and yellow is a signal that we readily build their relatively small nests under
recognize, informing
eaves. Paper wasps are
us that this insect is
rather inappropriately
capable of inflicting a
named since all the
painful sting to defend
social wasps build
itself or its nest. Yellow
their nests using paper,
I am not talking
jackets are members
i.e., masticated plant
about
a
warm
of a group of stinging
material. In fact, while
insects known as the
the yellow jacket and
and fuzzy
social wasps or vespids.
bald-faced hornet nests
bumblebee,
One sting is more than
are encased in paper,
but
a
cold
and
sufficient to instill a
the nests of the paper
measure of respect for
wasps are open and
steely yellow
these insects, and for
you can see the cells
jacket…
the one or two people
of the nest from below.
in a thousand who are
One entomologist
severely allergic to the
tried to introduce the
venom, one sting can
name “umbrella wasp,”
be a potentially life-threatening event. which describes their open nest, but old
Entomologists have tried to habits die hard.
quantify the pain inflicted by various
According to the aforementioned
insect stings. The Schmidt Sting Pain Schmidt scale and other sources
Index is a 5-point pain scale, numbered (including my wife, who recently had
from 0 to 4. The sting from a honeybee, an unfortunate encounter with some
yellow jacket, and bald-faced hornet all paper wasps in the pump house), the
rate a 2, which is classified as simply paper wasp sting is more painful than a
painful. The paper wasp sting rates yellow jacket or bald-faced hornet, but
a 3, or very painful. The rating of 4, the good news is that paper wasps are
extremely or excruciatingly painful, is generally nonaggressive and sting only
reserved for the likes of the tarantula when their nest is actively threatened.
hawk or the bullet ant, neither of which, (Note: Always check the pump house
luckily, are inhabitants of southern for paper wasp nests). As is often the
Oregon. Of course, pain is a subjective case, if you leave them alone, they
response and there is good evidence that will leave you alone. However, yellow
one’s pain tolerance is to a significant jackets and bald-faced hornets tend to
degree genetically determined. So if you be more aggressive in protecting their
have a low pain tolerance, it is not that nests, and that is usually when people
you lack courage or fortitude, you were get stung.
most likely born that way.
All these wasp nests are used only
The social wasps that we contend for a single year and are started by a
with locally are several species of queen in the spring, so the nests start
yellow jackets, including the bald-faced out very small and increase in size over
hornet and a number of paper wasps. the summer. By the end of summer,
Most of these insects are beneficial in the nests of some species, such as the
that they are predators and consume western yellow jacket and the bald-faced
a variety of other insects and spiders. hornet, may have gotten very large, so
When encountered away from their there can be a lot of workers around
nest, they do not usually sting except and they will defend the nest vigorously.
when harassed. In our region, yellow In late summer it is not uncommon to
jackets are generally ground nesters, walk by a yellow jacket ground nest
using an abandoned burrow in which unawares and suddenly find yourself
to build their nest, although they may under attack. Plus, the stinger of social
occasionally use a wall void or similar wasps, unlike a honeybee, is not barbed,
cavity. Bald-faced hornets, although allowing them to sting repeatedly.
technically yellow jackets, are black The western yellow jacket (Vespula
pensylvanica) is by far the worst offender
in our area. This species has adapted to
become a scavenger, particularly late
in the summer, and this is the yellow
jacket that is commonly a nuisance at
picnics and barbecues. Since it is a
scavenger, it is generally able to find
ample food through the summer, and
the nests continue to grow so that
you can eventually have thousands of
individuals in a single nest.
As these social wasps do sting and
can be a nuisance, the question of how
best to control them is a common one,
but do not forget that these insects are
primarily predators and are beneficial.
Avoidance is always the first option,
but trapping and nest elimination may
be needed in some cases. Trapping
the yellow jacket queens in the spring
may be helpful in reducing the number
of nests in an area, and trapping in
the summer to reduce the overall
number of yellow jackets may be of
some benefit, especially in areas that
get a lot of recreational use. As for
nest elimination, this is done most
easily for paper wasps and bald-faced
hornets, whose nests are usually visible
and accessible. However, since paper
wasps are not very aggressive, their
nests should be left alone unless they
are in an area where they are likely to
be disturbed (such as a pump house).
As for ground nests, they are often
discovered late in the summer when
the nest is large. If avoidance is not
possible, it is generally advisable to
consult a professional, since spraying
nests, particularly ground nests, can be
both tricky and risky.
Richard Hilton • 541-772-5165
Senior Research Assistant/
Entomologist
Oregon State University
Southern Oregon Research
and Extension Center
richard.hilton@oregonstate.edu
Photos, top to bottom: paper wasp; nest of
paper wasp; yellow jacket; bald-faced hornet;
and nest of bald-faced hornet. Photo credits,
top to bottom: www.sutter-yubamvcd.org;
www.lawestvector.org; www.beneficialbugs.
org; www.indianahoney.com;
www.sierrapotomac.org.