The insects most beneficial to humans are found in
the large insect order Hymenoptera. Not only are the bees and many of their relatives
pollinators of flowering plants, including fruits and vegetables, but thousands of species
of small wasps are parasites of other arthropods including pest insects. Without these
parasites that limit the growth of insect populations, pests would overtake most crops.
The urban pests of the order Hymenoptera are the
stinging insects. Although the first image to come to mind implies danger to humans, these
yellowjackets, hornets, and wasps sometimes serve our interest: They feed their young
largely on flies and caterpillars.
Many of these stinging insects are social. They live in colonies with a caste system or a
division of labor and overlapping generations -- all offspring of one individual
reproductive. Some of these colonies persist for many years (ants, honey bees) and others,
like stinging wasps, start anew each year.
THE AFRICANIZED BEE
The Africanized bee is the same species as the European honey bee kept by beekeepers all
over the United States. Introduced into Brazil from southern Africa, it is adapted to
longer warm seasons than are northern honey bees.
It is thought that this bee will advance as far into the northern temperate region as it
has into the southern temperate region. If this is true, Africanized bees will be
distributed north in a line that will reach from southern Pennsylvania, west to Seattle,
Washington.
Africanized bees do not store as much honey to take them through the winter as honey bees
do. They have smaller colonies and tend to swarm more often. Smaller swarms allow colony
development in smaller cavities. In South and Central America, Africanized swarms settle
in hollow trees like northern honey bees; they also colonize in rubber tires, crates and
boxes, wall voids, abandoned vehicles and other protected places that abound in urban
areas. Worker bees tend to mob intruders. The urbanized Africanized honey bee presents a
new management challenge not only to beekeepers but to urban pest management technicians.
CARPENTER BEES (Xylocopa)
Carpenter Bees are not social insects; they live only one year. The most common Carpenter
Bee, Xylocopa virginica, is distributed throughout the eastern half of North America. This
bee is a large insect with a hairy yellow thorax and a shiny black abdomen. Superficially,
it resembles yellow and black female bumble bees, which are social and more closely
related to honey bees. Western Carpenter bees are also large, shiny, sometimes metallic,
and are shaped like bumble bees.
Carpenter bees bore in wood and make a long tunnel provisioned with pollen and eggs. They
prefer to enter unpainted wood and commonly tunnel in redwood and unpainted deck timber.
They will also go into painted wood especially if any type of start hole is present. New
females reuse old tunnels year after year; they are also attracted to areas where other
females are tunneling. Egg laying and tunnel provisioning occurs in the spring. Males
hover around the tunnel entrance while the female provisions the nest and lays eggs.
Males dart at intruders belligerently but they can do no harm; they have no stingers.
Since these bees are not social, there is no worker caste to protect the nest. Stings of
females are rare.
New adults emerge after the middle of summer and can be seen feeding at flowers until they
seek overwintering sites, sometimes in the tunnels.
Habitat Alteration and Pesticide
Application
Carpenter bees drill into the end grain of structural wood or into the face of a wooden
member, then turn and tunnel with the grain.
Dust tunnels or inject with pressurized liquid insecticide. Insert a dusted plug of steel
wool or copper gauze in the tunnel; fill the opening with caulk, wood filler, or a wooden
dowel. [A dusted plug stops new adults who otherwise would emerge through shallow
caulking.] Caution should be taken, especially if technicians are working on ladders and
if they are not experienced with these rather harmless bees.
CICADA KILLER WASPS
Cicada killers are very large yellow and black relatives of mud daubers, however they do
not look like mud daubers. More than one inch long, they look like "monster"
yellowjackets.
Pest Management
Cicada killers can be ignored by those who accept an explanation of their harmless nature.
Each wasp, being a female, has a stinger; each can sting. Due to their size and fierce
looks, however, stings are extremely uncommon. When there is undue worry about these huge
wasps, open soil burrows can be dusted individually; the female will be killed when she
returns.
HONEY BEES (Apis mellifera)
The honey bee was introduced into the United States in Colonial America. Honey bees are
highly social insects and communicate with each other, relaying direction and distance of
nectar and pollen sources. Bees make combs of waxen cells placed side by side that provide
spaces to rear young and to store honey. The bee colony lives on the stored honey
throughout winters, and therefore, can persist for years.
When colony populations are high, the queen may move part of the colony to new harborage.
Bees swarm at this time, usually finding hollow trees to begin their new colony, but they
occasionally work their way into building wall voids.
Drones are male bees and they have no stingers. Drones do
not collect food or pollen from flowers. Their sole purpose is to mate with the queen. If
the colony is short on food, drones are often kicked out of the hive.
Workers, which are the smallest bees in the colony, are
undeveloped females. A colony can have up to 60,000 workers. The life span of a
worker bee depends upon the time of year. Her life expectancy can be as long as 35 days.
Workers feed the queen and larvae, guard the hive
entrance and help to keep the hive cool by fanning their wings. Worker bees also collect
nectar to make honey. In addition, honey bees produce wax comb. The comb is composed
of hexagonal cells which have walls that are only 2/1000 inch thick, but support 25 times
their own weight.
Honey bees' wings stroke over 11,000 times per minute,
thus making their distinctive buzz.
A honey bee colony in a house wall can cause major problems. The bees can chew through the
wall and fly inside. Their storage of large amounts of honey invites other bees and wasps.
Their detritus (e.g., dead bees, shedded larval skins, wax caps from combs and other
material) attracts beetles and moths.
When a bee colony is found in a building wall, it must be removed. Removal can be
accomplished by contacting a local bee keeper in your area. Your local Agriculture
Agent has names of all bee keepers close to you. Look in the blue pages of you phone
book for his number.
After the colony is moved you can safely remove the nest. If the nest is not removed, the
wax combs -- normally cooled by the bees -- will melt and allow honey to flow down through
the walls. Honey stain can never be removed; the walls will have to be replaced. As well,
the freed honey attracts robber bees and wasps. The comb wax will attract wax moths that
may persist for several years.
Finally, after the colony is moved the entrance hole should be caulked or repaired to
prevent further bee infestation.
Bee Stings vs. Wasp Stings
Honey bee venom contains almost 20 active
substances. Melittin, the most prevalent substance, is one of the most potent
anti-inflammatory agents known. It is 100 times more potent than
hydrocortisol. Adolapin is another strong anti-inflammatory substance, and inhibits
cyclooxygenase, also creating analgesic activity as well. Apamin inhibits complement
C3 activity, and blocks calcium-dependent potassium channels, thus enhancing nerve
transmission. Other substances, such as Compound X, Hyaluronidase, Phospholipase A2,
Histamine, and Mast Cell Degranulating Protein (MSDP), are involved in the inflammatory
response of venom, with the softening of tissue and the facilitation of flow of the other
substances. There are also measurable amounts of the neurotransmitters Dopamine,
Norepinephrine and Seratonin.
Wasp venom changes depending upon the type of wasp. Most
have similar ingredients to the bee but the make up is different in the percentages of
each ingredient. One of the main differences between the wasp sting vs. the bee
sting is the way the two inject their venom.
The wasp thrusts his shaft into the victim and
the lancets move rapidly backwards and forwards (sliding along the stylet) in a sawing
action. The lancets are barbed, meaning, they have small backward-pointed hooks
along their edges. As the shaft penetrates further into the victim's body, the barbs
allow anchorage against the flesh until the alternate lancet moves forward and 'claws' the
shaft deeper into the wound. The movement of the lancets also enables a pumping
action to take place at the abdomen end of the shaft. This causes the poison sac to
pump venom down through a central poison canal, between the lancets and out through the
shaft tip into the wound. Both Bees and Wasps sting their victims using a similar
process but there is an essential difference, especially important when the victim being
stung is a human-being. Bee lancets have larger barbs than wasps. The bee is
unable to rip the shaft back out through the wound due to the barbs' resistance against
the firmness of human flesh. The wasp stinger has lancets with very small
barbs, more like fine serrated edges. A wasp can extract the shaft and fly off
contented with having executed a nasty attack on the hapless victem. On the
other hand the poor old bee ends up having his entire stinging apparatus, poison sac and
all, wrenched out of its abdomen. The bee will later die due to the damage caused.
MUD DAUBER WASPS (Family Sphecidae)
Mud Dauber wasps are not social wasps like Paper wasps. They are in a different family.
Many paralyze spiders to provision mud cells built to enclose eggs, larvae and pupae. The
mud cells form long clay tubes or large lumps. The wasps are slender; they are shiny black
or brown, orange or yellow, with black markings. Many have long slender thread waists.
Like Carpenter bees there is no protective worker caste; these wasps are not aggressive;
they will not sting unless pressed or handled. Mud Daubers place their mud nests in
protected places like electric motors, sheds, attics, against house siding and under porch
ceilings. So many wasps congregate at the same site to construct the mud nests that later
removal of the nests and repainting is often expensive.
Habitat Alteration and Pesticide Application
Mud daubers are killed easily with aerosol contact sprays. Scrape away mud nests, and
cover problem areas with a good quality smooth paint. Nesting should be discouraged on
porticos and high porches of historically important buildings.
HORNETS, WASPS, AND YELLOWJACKETS
In parts of the United States, particularly in the eastern states, yellowjackets, wasps,
hornets and bees are all called bees by the general public. Of course the general public
is principally focused on one attribute these insects have in common -- their stingers.
Knowledge of the behavior of these pests is essential to their management; effective
communication with frightened or, at best, fearful clients is an important skill
technicians must develop.
Nests of stinging pests are usually the target for control. Understanding nesting and the
make-up of the colony is essential.
NESTS AND COLONIES
Yellowjackets, hornets and paper wasps are all in the same insect family, Vespidae. The
common Paper wasp with its umbrella shaped nest or single comb best demonstrates the basic
building pattern of a colony.
THE GIANT HORNET (Vespa crabro)
Technically, this wasp is the only hornet in North America, but it did not originate here;
it was introduced from Europe. It is found in the northeastern quarter of the United
States; it ranges as far south as North Carolina and Tennessee with scattered sightings
extending west of the Mississippi River.
The Giant hornet is reddish-brown and yellow and almost an inch long. It builds its nest
mainly in hollow trees, and in wall voids of barns, sheds and sometimes houses. An open
window or door is an invitation to hornet workers, and they frequent buildings under
construction. Their large combs and envelope are constructed of partially decomposed wood
and, like the Eastern yellowjacket, are very brittle. Workers of the Giant hornet capture
a variety of insects including bees and yellowjackets to feed their young. Workers also
have a habit of stripping bark back from some shrubs -- especially lilac. As they girdle
the branches, they lick the sap from the torn edge. They will sting humans, and the sting
is painful.
PAPER WASPS
Paper wasp queens, like other Vespid nest mothers, is the lone female reproductive, who
begins her nest by attaching a thick paper strand to an overhanging structure. She then
builds hollow paper cells by chewing wood or plant fibers (cellulose) mixed with water and
shaped with her mouthparts.
When a half dozen cells or so are hanging together, the Queen lays an egg near the bottom
of each one. The little white grubs that hatch from the egg glue their rear ends in the
cell and begin receiving nourishment in the form of chewed up bits of caterpillars
provided by their mother. When they grow large enough to fill the cell cavity, they break
the glued spot and hold on their own by their stuffed fat bodies, hanging head down.
Mature larvae, then, spin silk caps, closing off the cell, and molt into pupae. This same
larval behavior pattern is followed by yellowjackets and hornets also. All are females.
Other than their white color, these Vespid pupae look like adults; they develop adult
systems, then shed their pupal skins, chew through their silk cell cap, pump out their
wings, and take their place as worker assistants to their mother. (Paper wasp queens and
workers are the same size; yellowjacket and hornet queens are larger than their
daughters.)
From Spring on, the queen lays eggs and the daughter workers feed larvae and expand the
comb or nest. They do not eat the protein (insect) food they gather for the larvae but get
their energy from flower nectar. Later in the season, some of the larvae develop into
males and others will become next year's queens.
The new males and females mate with those of other colonies, and the fertilized females
find hiding places under tree bark or in logs and wait out the winter until they can begin
their new colony in the spring.
The male Vespids die in winter, likewise the nest disintegrates and will not be used
again.
MANAGEMENT AND CONTROL OF PAPER
WASPS (Polistes)
Paper wasps nests are often found near doorways and other human activity areas without
occupants being stung. Colonies can become problems, but when they do, Paper wasps can be
controlled easily.
When attracted to fallen ripe fruit, these wasps sting people who venture into the same
area. Colonies in trees, out buildings, hollow fence posts and other protected places are
not as easy to control as those from nests on structures.
Habitat Alteration
Remove old nests and scrape the point of attachment. [This spot is often selected by
new queens for attachment of new combs.]
Remove ripe fallen fruit as
often as possible.
Caulk openings in attics,
window frames, and around wall penetrations to keep overwintering females out of unused
rooms and spaces.
Pesticide Application
Use pressurized sprays that propel spray for 8-12 feet or use aerosols on extension
poles especially manufactured for aerosol cans.
If a ladder is needed wear a
bee suit and veil. Proceed cautiously.
YELLOWJACKETS
Yellowjacket (with eighteen species in North America) colonies begin with a large
fertilized queen; she develops smaller daughter workers and later reproductives just as
the Paper wasps, but the nest structure is not the same. Some yellowjacket nests hang in
trees and shrubs, and some are developed underground.
Aerial Nesters
Several yellowjackets make the aerial football- shaped paper nests, commonly called
hornets nests. Two of these yellowjackets are common: the Aerial yellowjacket,
Dolichovespula arenaria, and the Bald Faced hornet, Dolichovespula maculata.
The Aerial yellowjacket is found in the west, Canada, and east ( but not in the central
and southern states). This species begins its nest in March or April and is finished and
no longer active by the end of July. Their nests, usually attached to building overhangs
are smaller and more round than those of other species.
The Bald Faced hornet is larger than the other yellowjackets and is black and white -- not
black and yellow. It lives along the west coast, across Canada, and in all of the states
in the eastern half of the country.
On warm spring days, the large Aerial nesting queen develops a small comb, like the Paper
wasp with a dozen or so cells, but she encloses it in a round gray paper envelope. The
daughter workers later take over the nest duties, and by mid summer, when the worker
population is growing and food is plentiful, the nest is expanded to full size. A
full-sized Bald Faced hornet nest consists not of a single umbrella comb like the Paper
wasp, but four to six wide circular combs -- one hanging below the other and all enclosed
with an oval paper envelope consisting of several insulating layers. Bald faced hornets
not only gather flies, but are large enough to kill and use other species of yellowjackets
for larval food. They attach their nests to low shrubs or high in trees or on buildings.
Although Aerial colonies can have four to seven hundred workers at one time, their food
gathering habits do not routinely bring them in contact with humans. Large nests are often
discovered only after leaves have fallen and the nests are exposed -- both to view and to
nature's elements that finally bring about their disintegration.
Underground Nesters
The stinging wasp, often identified as a yellowjacket, is black and yellow. Primarily
yellow bands cover a dark abdomen. These species are in the genus Vespula.
They begin their nests like the aerial nesters -- with an enveloped small comb made of
wood fiber paper. Only these nests are started in soil depressions, rodent burrows, or in
any small hole in the ground that will give protection until workers can develop.
Once workers begin nest care, they enlarge the entrance hole and expand the nest. Combs
are placed in tiers, one below the other. They can be very large; they have firm support
from the soil surrounding the external envelope. Several species of Vespula make their
nests in building wall voids, attics, hollow trees and other enclosed spaces as well as
the ground.
Both Aerial and Ground Nesters
Of the thirteen species in North America, only a few require pest management. These few
species have certain characteristics and habits that put them on a collision course with
people:
They can live in what might be called disturbed environments (areas that have been
changed to suit human activities in urban settings) such as yards, golf courses, parks,
and other recreation areas.
They have large colonies --
some will develop thousands of workers.
Their habits do not restrict
them to a specific kind of prey. Foraging workers capture insects for their larvae and
nectar and other sweet carbohydrates for themselves where they can find it. Essentially,
they are scavengers and work over garbage cans and dumpsters. They especially enjoy
picnics and football games.
One can easily see that these habits put a large number of foraging stinging insects into
close association with large populations of humans.
THE COMMON YELLOWJACKET
Vespula vulgaris
V. vulgaris ranges across Canada and the northeastern United States. Common in higher
elevations, it nests in shady evergreen forests around parks and camps in the western
mountains and the eastern Appalachians. This species also is one of the most important
stinging insects in Europe.
THE EASTERN YELLOWJACKET (Vespula
maculifrons)
This common ground nesting yellowjacket is distributed over the eastern half of the United
States. Its western border is from eastern Texas north to eastern North Dakota. Workers
are slightly smaller than most yellowjackets, but colony size can number around 5,000 or
more individuals. The nest of V. maculifrons is dark tan, made of partially decomposed
wood and is quite brittle. The Eastern yellowjacket sometimes nests in building wall
voids.
Most yellowjackets have very slightly barbed stingers but the sting will not set in the
victim's tissue like the barbed stinger of the honey bee. The stinger of V. maculifrons,
however, often sticks and when the insect is slapped off, the stinger may remain.
THE GERMAN YELLOWJACKET (Vespula
germanica)
In Europe, German yellowjacket nests are subterranean, but in North America the vast
majority of reported nests are in structures. This yellowjacket is distributed throughout
the northeastern quarter of the United States. Nests in attics and wall voids are large,
and workers can chew through ceilings and walls into adjacent rooms. The nest and nest
envelope of this yellowjacket is made of strong light gray paper. Colonies of this
yellowjacket may be active in protected voids into November and December when outside
temperatures are not severe.
MANAGEMENT OF YELLOWJACKETS
Problems with yellowjackets occur mainly when:
Humans step on or jar a colony entrance.
A colony has infested a wall
void or attic and has either chewed through the wall into the house or the entrance hole
is located in a place that threatens occupants as they enter or leave the building.
Worker yellowjackets are no
longer driven to feed larvae in the late summer months, and they wander, searching for
nectar and juices -- finding ripe, fallen back yard fruit, beer, soft drinks and sweets at
picnics, weddings, recreation areas, sporting events and other human gatherings.
Yellowjackets are sometimes responsible for injections of anerobic bacteria (organisms
that cause blood poisoning). When yellowjackets frequent wet manure and sewage they pick
up the bacteria on their abdomens and stingers. In essence, the stinger becomes a
hypodermic needle. A contaminated stinger can inject the bacteria beneath the victim's
skin. Blood poisoning should be kept in mind when yellowjacket stings are encountered.
Inspection
Sting victims often can identify the location of yellowjacket nests. Where the nest has
not been located look in shrubbery, hedges, and low tree limbs for the Bald Faced hornet.
Soil nests are often located under shrubs, logs, piles of rocks and other protected sites.
Entrance holes sometimes have bare earth around them. Entrance holes in structures are
usually marked by fast flying workers entering and leaving. Nests high in trees should not
be problems. Be sure to wear a bee suit or tape trouser cuffs tight to shoes.
Habitat Alteration
Management of outdoor food is very important.
Clean garbage cans regularly
and fit them with tight lids.
Empty cans and dumpsters
daily prior to periods of heavy human traffic at zoos, amusement parks, fairs and sporting
events.
Remove attractive refuse,
such as bakery sweets, soft drink cans, and candy wrappers, several times a day during
periods of wasp and yellowjacket activity.
Locate food facilities
strategically at late summer activities so that yellowjackets are not lured to dense
crowds and events. [The National Park Service in their IPM programs, found that stings
were dramatically reduced when drinks are served in cups with lids.]
Clean drink dispensing
machines; screen food dispensing stations, and locate trash cans away from food dispensing
windows.
To limit yellowjacket
infestations in wall voids and attics, keep holes and entry spaces in siding caulked;
screen ventilation openings.
Pesticide Application
When possible, treat ground and aerial nests after dark [Workers are in the nest at that
time]. More often than not, because of traditional work schedules, treatment will be
scheduled for the daytime.
Begin with the entrance hole in view and a good plan in mind.
Wear a protective bee suit. Unless these insects can hold on with their tarsal
claws, they cannot get the leverage to sting. Bee suits are made with smooth rip-stop
nylon which does not allow wasps and bees to hold on. A bee veil and gloves are part of
the uniform. Wrist and ankle cuffs must be taped or tied to keep the insects out of
sleeves and pant legs.
Move slowly and with caution.
Quick movements will be met with aggressive behavior. Move cautiously to prevent stumbling
or falling onto the colony.
Have equipment handy so one
trip will suffice.
Application
Insert the plastic extension tube from a pressurized liquid spray or aerosol
generator in the entrance hole; release the pesticide for 10 to 30 seconds. Resmethrin is
most effective.
If the pressurized liquid
spray includes chemicals that rapidly lower nest temperature (freeze products), be aware
that it will damage shrubbery.
Plug the entrance hole with
dusted steel wool or copper gauze. Dust the plug and area immediately around the entrance.
[Returning yellowjackets cue on entrance holes using surrounding landmarks and seeing the
shadowed opening. They will land at the entrance and pull at the plug picking up toxic
dust. Any still alive inside will also work at the dusted plug.
Aerial Nests
Cut aerial nests down and seal them in a plastic bag. [The queen and workers inside
will be dead, and larvae will fall out of their cells and die from either insecticide
poisoning or starvation. Pupae in capped cells may escape the treatment, however, and
emerge later.]
Be especially cautious when
using ladders to get at aerial nests or wall void nests. Set the ladder carefully and move
slowly.
Wall Voids
Approach the entrance hole cautiously; stay out of the normal flight pattern.
Watch first. Observe whether
yellowjackets entering the nest go straight in or to one side or the other.
Insert the narrow diameter
plastic tube in the hole in the observed direction of entrance and release pesticide for
10-30 seconds.
Dust inside the entrance and
plug it as with underground nests.
Remember, German yellowjacket
nests may remain active into December.
Use care not to contaminate
food surfaces.
Spraying trash cans and the outside of food stands will reduce or repel yellowjackets at
sporting events; the treatment will not last more than one day. Honey bees are also killed
with this control measure. Remember, do not contaminate food surfaces.
Follow-up
Ongoing monitoring throughout the active yellowjacket season is essential when a pest
management program is in place at parks, recreational areas, zoos and other outdoor
activity areas.