Although most often a domestic rather than a public-health problem, venomous
arthropod encounters occasionally require the response of public agencies. For
example, several mosquito-control districts assign personnel specifically for
control of honey bee and wasp problems. As the Africanized honey bee spreads in
the U.S., the demand for these services will increase. This chapter deals with
the major groups of venomous arthropods: the hymenopterans, spiders,
centipedes and scorpions, and urticating caterpillars.
More than 2,500 species of wasps occur in North America. About 50 of these
are troublesome to humans. They are divided into hornets and yellowjackets,
Vespa spp. and Vespula spp.; paper wasps, Polistes spp.;
mud daubers, Sceliphron spp. and Chalybion spp.; and velvet ants
(members of the parasitic wasp family Mutillidae).
Developmental stages. Yellowjackets, hornets and wasps have similar
life cycles. Adult forms include fertile females (queens), workers (females,
usually sterile) and fertile males. In late summer, colonies produce new queens
and males. After mating, these new queens go into hibernation in such places as
cracks in rocks, under loosened bark of trees, in buildings and holes in the
ground. Some paper wasps hibernate in attics and basements. Males and workers do
not survive the winter.
The following spring the queen emerges from hibernation and searches for a
suitable nesting site. She then collects wood or other vegetable fiber from
nearby plants and chews it into a paperlike substance for constructing a comb of
a few shallow cells (later enlarged into a nest). In each cell she lays an egg
and then protects the resulting larvae, feeding them daily with freshly
killed insects. After 12 to 18 days, the larvae spin cocoon caps over their
cells and transform into pupae. When adults emerge about 12 days later,
they serve as the first brood of workers, and the queen resumes egg laying.
Mud daubers, unlike the other wasp species discussed here, have no workers.
The female builds a nest of several clay cells. In each she places an egg and
several small paralyzed spiders. She then caps the cells and abandons the nest.
After hatching, the larvae feed on the spiders for several days, then pupate. In
about two weeks the adults emerge to start new nests. Mud daubers also
differ from other wasps in that they overwinter as larvae.
Among the mutillid wasps (velvet ants), females deposit single eggs in
suitable habitats, mostly on the larvae of other ground-dwelling wasps they
parasitize.
Bionomics. A single hornet or yellowjacket nest may have up to 15,000
workers and several hundred queens and males. Paper wasp nests are
single-layered, open-faced and umbrella-shaped. The size of the nest depends
upon the number of resident wasps and is incrementally enlarged to accommodate
the growing population. Their nests consist of multilayered combs surrounded by
a paper shell. In late summer, nests may contain up to 5,000 workers. A mud
dauber nest consists of several clay cells. Old nests are not reused.
These stinging insects are found throughout the country and can harm humans.
Three yellowjacket species cause concern: the eastern
yellowjacket, Vespula maculifrons; the southern yellowjacket,
Vespula squamosa; and the German yellowjacket, Vespula
germanica. Yellowjackets are named after their yellow and black striped body
markings. Worker yellowjackets are about ½ inch long. The eastern yellowjacket
and southern yellowjacket usually build nests in underground holes and only
occasionally in above-ground cavities. The German yellowjacket almost always
nests above ground. A large nest usually is about the size of a basketball.
Yellowjackets and hornets will aggressively defend their nests, and this
aggressiveness increases in late summer and fall. Because yellowjackets forage
for meats, sweets, ripe fruit and garbage, they pose a threat to humans even
when away from the nest. They are a particular problem in picnic areas, orchards
and around garbage containers.
The baldfaced hornet, Dolichovespula maculata, about 2/3 inch
long and black with whitish markings, is technically a yellowjacket but builds a
very distinctive pear-shaped, basketball-sized nest covered with grayish
paperlike material. It usually constructs its nest in a tree or shrub, or under
the eave of a building. The European hornet, Vespa crabro, is dark brown
with yellow and reddish markings and is about 1 ¼ inches long. It usually
nests in a hollow tree or log, or inside buildings. The nest is covered with a
brown envelope of coarse wood fibers. These hornets are beneficial because they
capture other insects. Often their nests are situated away from humans and, as a
result, are not harmful.
Mud daubers are solitary wasps of the family Sphecidae. They vary in length
from 1/2 to 1 1/4 inches and are very slender with threadlike waists. They build
mud nests in sheltered areas. These nests are tubelike cells, often positioned
side by side. Two common species are the black and yellow Sceliphron
caementarium and the metallic blue Chalybion californicum (it steals
the nests of S. caementarium, replacing nest contents with its own). Mud
daubers sting only if pinned against the skin.
Velvet ants, easily recognizable by bright red-orange or yellow
pubescence on the abdomen, are actually solitary wasps rather than ants. This
large group is mostly found in the southern and western parts of the U.S.
Females are wingless and usually smaller (measuring 1/3 to 1 inch) than males. They
have a characteristic red, orange or yellow pubescence covering the posterior
half of the abdomen and are most commonly seen scurrying along on the ground.
They inflict a painful sting when accidental encounters occur with humans.
The several species of paper wasps, all about 2/3 to 1 inch long, are
slender and variously colored with brown, red and yellow. They build their
single-comb, unprotected nest from the eaves of porches and buildings and other
sheltered locations. As with most other wasps, only the queen survives the
winter to start new colonies in the spring. Paper wasps are not as aggressive as
yellowjackets or hornets in defense of their nest.
The cicada killer wasp, Sphecius speciosus, is 1 1/2 to 2
inches long and brownish-black with yellow markings on the abdomen and face. The
female digs a burrow in the soil. It captures cicadas, paralyzing them by
stinging, and places them in the burrow. An egg is deposited on each cicada, and
that cell is closed off. Cicada killer wasps produce one generation per year,
with larvae spending the winter in the nest cell in soil. The only damage these
wasps cause is the creation of dirt piles, dug out to create nests, that usually
disappear with the first rain. While their size is intimidating, cicada killers
are not aggressive and will sting humans only if pinned against the skin.
Control. Individual foragers can often be discouraged or easily
dispersed. For example, a single wasp in an automobile can be gently pushed out
an open window using an object such as a folded newspaper. A yellowjacket on the
lip of a soft drink container should be gently coaxed away. To swat a wasp,
particularly while it is on skin, invites a sting. In fact, smashed or injured
yellowjackets release an alarm pheromone that greatly increases the
aggressiveness of other members of the colony. Good sanitation practices in
picnic and recreational areas are essential. Food garbage and empty beverage
cans should be placed in containers with tight-fitting lids.
Traps offer some control of foraging yellowjackets. One such trap employs a
dead fish suspended from a tripod above a tub filled with water containing a
wetting agent such as soap. Foragers are drawn to the odor and will often cut
away a piece of fish that is too heavy to carry and then fall into the water,
where the wetting agent prevents their escape. Another trap consists of a 6- to
8-inch-high flower pot with holes in the bottom. A screen wire cone with a
1/2-inch diameter hole at the tip is inverted over the holes in the bottom of
the pot and a bait tray with meat is suspended from a tight-fitting screen cover
for the top of the pot. Foragers enter through the holes in the bottom and pass
through the hole in the screen to get to the meat but then are unable to find
their way out. The trap is tied to a post or suspended from a tree branch about
4 feet above the ground, so that the top and bottom of the pot are unobstructed.
To kill the wasps in the trap, remove the trap and place it in a freezer
overnight.
Yellowjacket and hornet control efforts involve treatment of nests and
surrounding areas with a variety of formulations recommended for the specific
situations. Insecticides may be used as dusts, wettable powders,
solutions or emulsions. Rapid garbage disposal will reduce the numbers of some
species that congregate around garbage. The spraying of garbage containers once
a week, particularly around the tops, will help control these wasps. Residual
sprays are effective for control of wasps in buildings when applied to screens,
window frames, doorframes and other places where wasps generally crawl. Use
oil-based solutions with care when spraying outdoors to avoid damage around
vegetation.
Follow these guidelines when attempting yellowjacket or hornet control:
Most wasps are least active at night, when in the nest. Locate the nest
during daylight, then treat it after dark by directing the insecticide into
the nest opening.
Use a red-lens flashlight during the treatment to minimize wasp awareness.
Dusts are easy to apply to some hornet and yellowjacket nests whether
above or below the ground. However, it may be preferable in some circumstances
to use a formulation that tends to "freeze" the insects on contact.
There may be more than one entrance to underground nests.
If the ground is relatively smooth and soft around the entrances, placing
a metal or hard plastic container upside down over the entrance holes after
treating will help ensure control. Place weights on the containers to hold
them snugly against the ground.
The extension tube on a hand duster can be inserted into the nest opening.
Two or three strong puffs of dust filter through the nest and usually kill the
colony within 24 hours.
Solutions and emulsions should be sprayed into and onto the nests. The
more nearly saturated the nest, the quicker the kill.
Wear a protective bee suit when attempting to control yellowjackets.
Some people have tried to remove a hornet nest by suddenly covering it
with a plastic trash bag, tying the bag tightly to the branch, and then sawing
the branch off. Don't do it. Bald faced hornets can escape from trash
bags with ease.
Mud daubers are not usually subjected to control measures because they are
beneficial, but when necessary, undesirable nests can be knocked down and the
residual soil washed off with water and a brush.
Paper wasps are not as aggressive as yellowjackets or hornets in defense of
their nest. These nests should be eliminated only if they are located near human
activity. To do so, use a pressurized stream. Return a few hours later and
remove the nest to discourage others from nesting there.
Control efforts are not recommended for cicada killers, but, if control is
necessary, spray the soil where digging activity is observed.
Bees play an important pollination role in agriculture. For decades
entomologists have been including a strong statement about the protection of
bees in their insect control guides and pest management programs. However, when
bees become a threat to public health or the welfare of domestic animals, they
must be dealt with differently. Honey bees are more likely to require such
action than are bumble bees and the solitary bees.
Developmental stages. Bees undergo complete metamorphosis,
passing through the egg, larval and pupal stages to the adult. Eggs,
larvae and pupae are nurtured in cells within the hive by worker
bees. The social order can be quite complex, being dependent on physiological
influences of both worker and queen bees. Queens control whether the eggs are
fertilized and develop into females (workers) or unfertilized and develop into
males (drones). Virgin queens take flight and mate. After about three days, they
begin to lay eggs.
Honey bees. Honey bees, Apis mellifera, are about ½ inch
long with a fuzzy light brown to black appearance, with striped brown and black
abdomens. They are typified by their moderate size, hairy eyes, the ability of
the workers to sting only once, pollen baskets on hind legs of workers and the
strict caste system in which the queen performs no duties other than egg laying.
They are considered to be the one of the most beneficial insect species because
they pollinate plants and produce honey and beeswax. Because they sting in
defense of the hive or nest, however, honey bees become pests when colonies are
in the wrong location.
The life cycle of honey bees differs from that of hornets and wasps. After
the mating flight of new queens, the old queen leaves with a number of workers
(a swarm) to start a new hive. Only one of the fertile new queens is able to
return to the old hive where she begins laying eggs. Developmental time and
longevity in honey bees varies with each caste and among races (European,
Italian, African, etc.). After emergence as adults, honey bees continue to
develop reproductive organs (queens, drones) and to mature into queens, drones
and workers. A single queen may lay 1.5 million eggs in her three- to five- year
life, and may have as many as 100,000 offspring living at one time, although in
a typical colony there will be one laying queen, 20,000 to 60,000 workers, and
100 to 300 drones.
Wild colonies of honey bees nest in existing cavities such as hollow trees,
whereas domestic bees are housed in manufactured hives. Unlike other bees and
wasps, the honey bee may occupy the same nest from year to year. The queen and
many workers survive the winter in the nest. At various times new queens are
produced, resulting in the old queen and a number of workers leaving the hive to
"swarm" in search of a new home. Swarming is the natural means of honey bee
dispersion. A new honey bee colony is established after a swarm leaves an
established colony to seek a new location. The swarm flies from a few to several
hundred yards and lands on a low-hanging tree limb or other structure. From
there, scout bees seek out a suitable area to establish a new colony. Swarms may
stay in their temporary location from a few hours to a few days. During this
time swarms may be hived by beekeepers.
Absconding is a behavioral trait of all honey bees. Absconding occurs
when all of the adult bees, including the queen, workers and drones, leave the
old nest and relocate to a new site. Absconding is usually the result of a
severe disturbance such as predator activity, flooding, starvation or other
major stress. Absconding bees may travel 30 to 50 miles before finding a
suitable nest site. Long flights may have to be interrupted several times to
forage for food.
Stinging is a defensive behavior. Virtually all defensive behavior occurs in
the immediate vicinity of the hive. Away from the hive, bees literally have to
be forced to sting. Swarming bees are rarely defensive and do not sting unless
provoked. However, "hunger swarms" or absconding bees are usually very defensive
and are frequently the cause of stinging incidents. A bee's stinger is barbed.
When a bee stings a human or other large mammal, the stinger, poison sac,
surrounding muscles and nerves are torn from its body. Thus, the honey bee can
sting only once, and then soon dies. The stinger will continue to pump venom
until it dries up. An alarm pheromone (odor) is also released. This
pheromone will attract other bees to the area and prompt an aggressive response,
thus increasing the chances of additional stinging. Stimuli that have a tendency
to increase the defensive behavior of bees include sudden and rapid movements,
jarring or bumping hives or frames, vibrations and noise such as lawn mowers or
tractors, odors (both good and bad), and dark colors. Bees are more defensive in
cooler, cloudy weather.
The Africanized honey bee (AHB) is simply a hybrid honey bee
resulting from the natural cross of the European honey bee (EHB), Apis
mellifera mellifera, with an African honey bee, Apis mellifera
scutellata. This different genetic background causes the habits of the
Africanized bee to differ from the habits of the EHB. But identifying these
different races of honey bees and their hybrids is difficult. The
characteristics (morphological measurements, specific proteins, DNA or cuticular
hydrocarbon analysis) used for identification differ only slightly and overlap
considerably among individuals.
Since the intentional introduction into South America in the late 1950s of
the African honey bee, AHBs have received a great deal of attention concerning
their impact on human welfare. They are extremely sensitive to the slightest
nearby disturbance and are likely to respond with massive and persistent
stinging attacks. Compared to the EHB, the AHB is much easier to provoke,
responds quicker and in larger numbers when the colony is threatened, and
remains agitated for a longer period of time. Disturbing an AHB colony may
result in six to 10 times as many stings as an EHB colony. This phenomenon is
attributed not only to the AHB's more acute sensitivity but also to its response
to the alarm pheromone, the chemical odor that is released after stinging is
initiated. The AHB may swarm four to eight times a year, but in relatively small
numbers compared with an EHB colony, which typically swarms once every year or
two. Also, whereas absconding is rare in EHB colonies, it's rather common with
the AHB. Unlike other honey bees, the AHB will nest in almost any place that is
protected from the weather. Because the AHB is tropical in nature, it may not be
able to regulate its body temperature as efficiently as the EHB and studies
indicate that the AHB does not form as efficient a cluster during cold weather
as the EHB. Swarms of AHBs are reported to often take over EHB colonies,
particularly colonies that do not have functional queens. However, EHB swarms
will do the same. AHBs are difficult to manage commercially and have a strong
tendency to abscond and settle elsewhere, which makes them a persistent threat.
Experience has taught that the AHB warrants concern but not hysteria, which may
lead to unwise management decisions.
The AHB spread throughout Brazil by swarming and absconding and continued to
spread northward through Central America and Mexico at about 200 to 300 miles a
year, reaching Panama in 1980, Mexico in 1985 and the U.S. in 1990. In advance
of this natural spread, numerous introductions were detected in the U.S. as
early as 1979 and as far north as Baltimore, Md., and Strong Point, N.Y. Upon
detection, these swarms were eliminated, thus preventing the establishment of
the AHB in the U.S. at that time. They now are present in the southwestern U.S.
Solitary bees. Sweat bees, mining bees, leaf-cutting bees and others
make up a rather large group of small-bodied solitary bees (up to ½ inch
long). Most of these bees nest in the soil, and often a large number of them
will nest close together, usually in areas with sparse vegetation. Occasionally,
some may nest in natural cavities such as in wood. Sweat bees get their name
from an attraction to people who are perspiring. They rarely sting except when
pinned against the skin. Some species of mining bees may be attracted in large
numbers to swimming pools. All of these types of bees are beneficial because
they pollinate plants. Controlling them is undesirable even if one could do so.
Bumble bees. Bumble bees of the genus Bombus are robust and
densely covered with black and yellow hairs (setae), the pattern of colors
varying with species. They range from about ½ to 1 inch long. Bumble bees are
social insects, nesting in existing cavities, usually on or in the ground. They
often use abandoned mouse and bird nests or anything containing cotton or other
soft materials. Only fertilized queens survive the winter. In the spring, the
new queen finds a nesting site, partially fills it with dry grass or moss, adds
bee bread (a mixture of pollen and nectar) and then adds eggs. She cares for
this first brood until the new workers take over all of her duties other than
egg laying. Bumble bees seldom enter structures and do not behave very
aggressively except in defense of their nest. They normally are a nuisance only
if they have built a nest close to human activity.
Control of bees. When bees colonize an area frequented by humans or
domestic animals, they become a pest or health risk. At such times they must be
removed or eliminated. Bees that need to be removed fall into two categories:
swarms and established colonies.
Bee swarms. A swarm of honey bees is a temporary inconvenience that
may last a few hours and then move away as soon as the bees find a new home.
Only in unusual situations will a swarm remain to build a comb and not move from
a cluster site. Honey bees in a swarm are usually gentle because they have
stomachs full of honey. If left undisturbed, a swarm will locate new quarters
and often disappear as quickly as it appeared. In the past, local beekeepers
collected swarms to put into unused hives, sometimes charging a nominal fee.
Capturing swarms is relatively easy because bees are not defensive when
swarming, and this was a common method of obtaining bees by hobbyists and
commercial beekeepers. Capturing wild swarms is not recommended for those who
aren't familiar with the habits of bees and don't have the proper protective
equipment.
Swarms seldom stay for long before scout bees find a suitable site to
colonize. However, it may be desirable to eliminate swarms in an effort to
prevent AHB colonization of certain sites, such as in or near dwellings. Swarms
may be eliminated with approved insecticides or by spraying with soapy water
using a high volume spray to achieve the best effect. Liquid dishwashing soap at
a 5 percent solution is recommended (1 cup of soap/gallon). Avoid fine mists.
Feral colonies. Although feral colonies seldom cause problems unless
provoked, they should be eliminated if they are established in an area where
interaction with humans or domestic animals may occur. Numerous insecticides are
approved for bee control. Soapy water doesn't work effectively because honeycomb
prevents adequate coverage. Colonies may be removed physically by hand or by
vacuuming with special types of vacuums. Once collected, the bees can be placed
in a hive, released at a different location or killed with insecticide.
Colonies nesting in structures such as attics, between the wall studs of
houses or garages, within porch roofs, or in similar areas are a great problem
because there is no easy, convenient method of removing the bees. Every effort
should be made to determine the extent of the nest and to give priority to
removing and relocating the bees, brood and honey stores. Simply killing the
bees will only make for more complex problems in the future. An unattended nest
of beeswax, honey, brood and pollen will attract other insects and animals. Wax
moths will enter to consume the wax, and cockroaches and ants will find the
brood and honey. Decaying brood and fermenting honey will cause undesirable
odors. Melting wax and honey can soak into walls, making them impossible to
paint or wallpaper. Walls will also remain moist to the touch for a considerable
period of time. If removing the bees and their nest is not practical, then other
methods of dealing with them can be considered. The following steps are
appropriate guidelines.
Locating bees. The first step in eliminating the pest problem is
locating the nest and getting rid of adult bees. The comb may be some distance
from the entrance/exit used by the bees, making it difficult to locate. If bees
are inside a wall with sheet rock on one side, feel the sheet rock for warmth;
tap the sheet rock and listen for a solid sound vs. a hollow sound. Listen also
for buzzing when tapping. If bees are in a wood, brick or sheet rock wall, when
you think you have located the nest, drill a hole (1/16 inch) large enough for a
coat hanger wire. Straighten out a coat hanger and stick it in the hole. You
should have honey or wax on the hanger when you withdraw it. Work close to the
top of the wall with holes and coat hanger because bees always hang the
honeycomb down from an overhead support.
In some instances, it will be quite expensive to attempt removal of the
nest. The owner may be willing to put up with the smell and the damage from
honey-soaked walls. Aerosol sprays may be very effective if sprayed through the
holes drilled for the coat hanger probe. It may be necessary to drill a number
of holes to inject an aerosol spray or dust. Insecticide should be applied at
the entry/exit area of the nest and, if feasible, directly onto the nest
(through holes drilled for this purpose). Several repeat applications are
usually necessary to kill the bees.
Handling bee problems. It is better to prevent bee stings than treat
them. Prevention can be enhanced in several ways. "Safening" is a term used for
action taken to modify a habitat, a structure, or other factor that will result
in a safe environment for people or domestic animals. With respect to bees, this
is usually action taken to reduce or eliminate a population. It could also be
action taken to prevent or discourage bees from colonizing an area. Structures
may be made safer by locating and removing bee colonies; reducing access to
desirable nesting sites by discarding barrels, old appliances, abandoned cars
and piles of debris; removing other materials, hollow trees and logs; filling
cavities in landscape trees with foam insulation; repairing loose insulation
beneath mobile homes and open vents beneath homes or attics; screening vents,
knot holes and cracks with wire mesh small enough to prevent bee entry; and
closing or filling openings for utilities and plumbing to prevent entry of bees.
Insofar as is practical, inside and outside facilities of parks and
recreational areas should be thoroughly inspected, bee colonies eliminated and
modifications made to prevent future colonization. High-use areas, such as camp
sites, boat launches and picnic areas should be re-inspected periodically to
remove any new colonies of bees. In large wooded areas used for recreational
purposes or training sites, signs may be posted informing people that bee swarms
may be encountered, requesting that such swarms not be disturbed and directing
that swarms be reported to appropriate authorities.
Bees do not like the noise, vibrations or air movement created by lawn
mowers and other power equipment. A quick inspection of an area to be mowed or
shredded can detect bee or wasp colonies that would be disturbed by such
actions. Removal of bee colonies prior to mowing dramatically reduces the
likelihood of multiple stings. Similarly, some large equipment will incite an
attack — especially with the AHB — from the engine noise and exhaust, or simply
by hitting the colony. The most likely victims are operators of vehicles with
open cabs, such as jeeps, Humvees, bulldozers, backhoes and tractors. Avoidance
can be maximized if the cab can be quickly closed in the event an attack begins.
Domestic animals are subject to bee stings. Wherever the AHB becomes
established, the number of animal deaths due to bee stings is predicted to
increase four to five times. Animals not confined seldom receive many stings
because they usually flee the area defended by the bees. Animals in pens or tied
cannot run away and may receive a lethal dose of venom. Animals should not be
confined or tied before the area is checked to make sure that no bee colonies
are established nearby.
Bumble bees and solitary bees seldom require insecticidal control. However,
when large numbers of mining bees invade swimming pools, they can be controlled
by treating the soil where they are nesting if it can be located. In the same
manner as yellowjacket and hornet treatments, bumble bee nests can be treated
safely after dark with the aid of a red lens or a lens covered with red
cellophane, as bees and wasps cannot see red. It is important to wear a
protective bee suit and tape trouser cuffs to shoes when attempting to control
bees.
Scorpions. Scorpions make up a small order (Scorpiones) of arthropods
related to spiders. Scorpions have eight legs, a combined head and thorax
(cephalothorax) and a segmented abdomen. They have a pair of large
pincerlike pedipalps at the front of their bodies, which they use for
catching prey. Their abdomens are segmented with an elongated tail ending in a
stinger, usually elevated over the body.
Scorpions feed on spiders and soft-bodied insects. Small prey may be eaten
immediately, while larger prey are stung and then eaten after movement stops.
Scorpions hide during the day and are active at night. They tend to live under
boards, stones or other objects, or beneath loose bark on trees and logs.
Indoors, they are most often found in crawlspaces and attics. Although scorpions
tend to be found on dry land, they require moisture and may be attracted to
water sources. They generally do not like extremely high temperatures and may be
driven to enter the living areas of homes seeking relief from heat and dryness.
Several species of scorpions are found in the U.S., with most inhabiting
areas in the South and Southwest. The most dangerous species in the U.S.,
Centruroides exilicauda, is limited to the Southwest. A widely
distributed species is the striped scorpion, C. vittatus. Adult striped
scorpions are yellowish-tan with two broad, darkened longitudinal bands on the
top of the abdomen. They are up to 2 ½ inches long. The female produces living
young, which she carries on her back for five to 15 days until they leave and
become independent. Adult life span ranges from two to five years.
Poison glands are located in the bulbous last segment of the abdomen, which
ends in the stinger. Scorpions rarely sting humans except when pinned against
the skin. The sting of the striped scorpion usually causes a localized painful
swelling and discoloration at the sting site. The effect lasts only for a few
hours and has been described as being similar to a bee or wasp sting. However,
fatal stings have been reported in the Southwest.
Centipedes. Centipedes, in the class Chilopoda, are most numerous in
the southern half of the U.S. but are widely distributed. They are generally
nocturnal, hiding during the day under rocks or similar shelter and in
crevices, closets, basements and other humid, protected locations. Prey consists
of insects and other small arthropods encountered during foraging. Two powerful
claws, located immediately behind the head, inject venom into such victims and
humans that inadvertently step on them or pick them up. In the U.S., most
centipedes are small and not a threat to humans.
Control. Sanitation is important to minimize scorpion
encounters. Boards, stones, wood piles and similar harborage sites should be
removed from around the house. Firewood and lumber should be stored off the
ground. During dry weather, scorpions may be collected after being aggregated by
attraction to wet burlap bags spread on the ground around the house. They then
can be killed by crushing with a heavy object. Eliminating and excluding insect
populations by caulking or other means of closing cracks under and around doors
and windows helps because it removes the scorpions' food source. Ducks and
chickens maintained in the yard around a house will eliminate most scorpions.
Applying a barrier strip of residual pesticide around the house helps to
reduce infestations. Spray the ground from the foundation out about 10 feet and
the foundation from the ground up about 2 feet. Particular attention should be
paid to treating weep holes in brick veneer and around basement window wells.
Attics, wall voids and crawlspaces are best treated with dust formulations;
residual crack and crevice sprays also help.
Complaints about the large centipede, Scolopendra subspinipes,
usually occur after heavy rains when flooding forces them to seek shelter in
homes. Caulking of spaces between walls and concrete floor slabs of poorly
constructed homes reduces the likelihood of entry into homes. Removing rocks,
wood piles and other trash eliminates harborage sites. Chemical control with
dusts or wettable powder formulations gives better residual control than
emulsions for centipedes, but generally centipedes are not sufficiently numerous
to warrant chemical control.
The immature stages of several species of moths in states east of the Rocky
Mountains are venomous to humans because of their external poisonous spines and
hairs. Some species are infrequently encountered, but three species are more
nationally common.
The Io moth caterpillar, Automeris io, when fully grown is
about 2 to 3 inches long with a row of tubercles armed with green and
black spines, many of which are connected to poison glands. This insect
undergoes one or two generations per year and overwinters in the pupal stage.
The caterpillars are encountered as they feed on favored vegetation.
The white to dark gray puss caterpillar, Megalopyge
opercularis, is about 1 inch long when fully grown and completely covered
with venomous hairs that resemble tufts of cotton. The moth undergoes two
generations a year in the Southeast, during which the caterpillars feed on
shrubs and bushes where they pose a threat to humans.
The saddleback caterpillar, Sibine stimulea, feeds on shrubs,
bushes, trees and other plants. Easily recognizable by the brown or purplish
saddlelike coloration on its back, it has multiple stout, venomous spines along
the sides of the body and the four tubercles.
Specific control activities are usually not warranted for these pests.
Public education and an awareness of the hazards are usually sufficient to
prevent repeat exposures. However, if necessary, insecticides registered for use
on plants can be used to control these pests.
The various sting mechanisms in these parasites and predators are usually
modified ovipositors. The venom produces lethal or narcotic effects in prey, and
the stings of many are very well-suited for defensive use. While unprovoked
stinging of large animals is considered rare, very little provocation is needed
to incite some stings in nest areas. Whatever their reasons for stinging, hymenopterans
kill more people in the U.S. each year than do snakes and spiders combined.
Although serious reactions from stings occur in only a very small percentage
of the population, everyone should be aware of the possibility of medical
complications that might result from stings to themselves, children and others.
The lethal dose of bee venom, for example, for humans is about 10 stings per
pound of body weight, assuming all of the bee's venom is injected by the sting.
So deaths due to the toxic effects of EHB venom received in multiple stings are
extremely rare. The venoms of the AHB and the EHB are almost identical, but the
increased stinging activity of the AHB makes it more dangerous.
But, for the 1 to 4 percent of the population hypersensitive to
honey bee and other venoms, one sting can be fatal. Reactions to stings range
from slight pain and swelling to much more serious symptoms, including
anaphylaxis. Early symptoms of an allergic reaction include a tingling
sensation on the palms, bottoms of the feet, tongue and lips; tightening of the
throat; dizziness; and nausea. Allergy tests are available but can be expensive.
If their normal routine does not bring them in contact with venomous arthropods,
people should not have to take the test. But for beekeepers or others who work
where hymenopterans are present, such testing is usually recommended.
Firefighters or police officers who may respond to emergency calls for insect
stings should be tested. Allergy testing will determine how sensitive a person
is, and a person's immunity can be built up with small, regularly scheduled
injections of venom. Kits are available as a prescription item for people who
are allergic to stings. Such kits are equipped with syringes and epinephrine for
emergency treatment. Doctors, emergency medical services, and other health care
personnel are well-educated in the diagnosis and treatment of stings and
anaphylaxis.
In the U.S., deaths from all hymenopterous insects (bees, wasps,
yellowjackets, ants) average between 40 and 50 per year. The arrival of the AHB
in the U.S. has created a public awareness of the associated health risks. This
awareness provides an opportunity to educate the public on medical aspects of
the AHB and other stinging insects.
First aid for sting victims. If the victim is showing no signs of
dizziness or difficulty in breathing, or has been stung only once, practical
first aid measures are:
Remove the sting with a sideways scraping movement of a fingernail, credit
card or dull knife to prevent more venom from being pumped in by the venom
sac.
Apply a paste of baking soda and cold cream or of wet salt within five
minutes of sting, when possible, and apply an ice pack to relieve pain and
calamine lotion to relieve itching.
Watch for any unusual reaction, such as the appearance of red blotches
anywhere on the body within two to 20 minutes, or breathing difficulties.
Breathing difficulty indicates a serious response, requiring medical attention
within 15 to 20 minutes.
Seek medical attention immediately if a person with health problems is
stung by an insect.
Stay with the victim until medical care is obtained.
At-risk groups. Certain groups in the population may be considered
at-risk for incidents involving venomous arthropods. Children are exposed to
habitats that increase the chance of interaction with stinging insects; plus,
they have a greater tendency to disturb those insects. Because of low body
weight, children may be particularly susceptible. The physical condition, health
and immunological status of the elderly place them in the at-risk group; they
should be prepared. Sportsmen, the handicapped, outdoor workers, military
personnel, etc., should be considered at risk when their work involves exposure
in habitats likely to be occupied by stinging arthropods. The risk is greater
when operating mowers, weed eaters, heavy equipment, chain saws, or other
equipment that can provoke defensive behavior from arthropods. Workers unable to
flee, such as those on poles or scaffolding, are at higher risk.
This chapter printed from the University of Florida and the American
Mosquito Control Association Public Health Pest Control WWW site at
http://entomology.ifas.ufl.edu/fasulo/vector/