Scorpions
Scorpions are arachnids, close relatives of
ticks, mites and spiders. They are easily rec
-
ognized by their characteristic shape. Scor
-
pions prefer dry habitats but occur throughout Texas.
They can be a nuisance when they interact with
humans because they will sting when disturbed.
Description
A scorpion’s body becomes more slender toward
the end and has a five-segmented tail that can be
arched over the back. On the end of the tail is a bulb-
like poison gland or stinger. Scorpions have four
pairs of legs and two large, pincer-bearing arms
(pedipalps) in front. Scorpions are well-equipped to
defend themselves or attack prey with their pincers
and stinger. Between the last pairs of legs are comb-
like structures called the pectines, which are sensory
organs used to sense surface textures and detect prey.
Scorpions have two eyes on the top of the head
and usually two to five pairs of eyes along the front
corners of the head. They do not see well, however,
and must rely on the sense of touch, using their pec
-
tines and other organs for navigation and detecting
prey. They have a well-developed sense of hearing.
Worldwide, scorpions range in size from ½ inch to
7 ¼ inches long (including the tail), depending on
the species.
The most common species in Texas is the
striped bark scorpion,
Centruroides vittatus
(Fig.
1). Adults are about 2 ½ inches long. Striped bark
scorpions are yellowish tan with two broad, dark
stripes running the length of the back and a dark
triangular mark on the front of the head above
the eyes. Populations in the Big Bend area may be
only faintly marked or completely pale. Immature
striped bark scorpions may be lighter in color. In
young scorpions, the base of the pedipalps and the
last segment behind the abdomen are dark brown
or black. This species can be identified easily by its
slender pedipalps (pincer-bearing arms) and long,
slender tail. The tail is longer on males than females.
Figure 1. Striped bark scorpion.
2
Biology
Scorpions are nocturnal, hiding during the
day and becoming active at night. This behavior
helps them manage temperature and water bal
-
ance, which are important functions for survival
in dry habitats. Many species dig burrows in the
soil. Their bodies are flat, which allows them to
hide in small cracks and under stones, bark, wood,
or other objects on the ground. From these hiding
places they wait or search for prey. Chief foods are
small insects, spiders, centipedes, earthworms,
and other scorpions. Once they capture their prey,
they use their large pincers to crush and draw it
toward the mouth so the prey’s body juices can be
ingested.
Some scorpion species may live for 20 to 25
years, but the typical life span is 3 to 8 years.
Adult scorpions may have several broods of
young. Following an elaborate mating process that
lasts 24 to 36 hours, the female undergoes a gesta
-
tion period ranging from 5 months to more than
1 year. The young are born alive in semitranspar
-
ent sacs. As soon as the young scorpions free them
-
selves from these thin wrappers, they climb onto
their mother’s back (Fig. 2).
The striped bark scorpion mates in the fall,
spring or early summer and the gestation period
lasts about 8 months. Females usually give birth to
13 to 47 young, with an average of 31. The imma
-
ture scorpions molt 3 to 7 days after birth and
remain on the mother for another 3 to 7 days.
There are five or six molts to maturity. A striped
bark scorpion lives for approximately 4 years.
Taxonomic Status
About 90 species of scorpions have been iden
-
tified in the United States. Texas has 18 species,
but only one, the striped bark scorpion, occurs
throughout the state. It is the only species of scor
-
pion found in the eastern part of Texas, whereas
two species have been recorded near Austin, four
near Amarillo, three near Abilene, five near Fort
Stockton, eight in the Fort Davis region, eight near
Langtry, and 14 in Big Bend National Park.
Habitat
Scorpions are found in many types of habi
-
tats, including desert flats, sand dunes, desert and
mesic mountains, grasslands, pine forests, decidu
-
ous forests, and chaparral. Species are most diverse
in desert areas.
The striped bark scorpion can be found indoors
or outdoors in a wide variety of habitats. It is often
found under rocks or boards and in debris. Striped
bark scorpions are active foragers that do not burrow
and are distinctly associated with dead vegetation,
fallen logs, and human dwellings. It is common for
this scorpion to climb trees and walls, and they often
are found in the attics of homes. During periods of
hot weather, scorpions may move into living areas to
escape the high temperatures in attics.
Scorpion Stings
The sting of a scorpion may be painful or even
deadly, depending on the species. Of the 1,500 spe
-
cies of scorpions worldwide, only about 20 to 25
are regarded as dangerous. A scorpion’s venom is a
mixture of compounds, including neurotoxins that
affect the victim’s nervous system. Stings from dan
-
gerous species may cause paralysis, severe convul
-
sions, cardiac irregularities, breathing difficulties,
and even death. Antivenins are available in areas
where dangerous scorpions live.
Figure 2. Female scorpion carrying babies on her back.
Already capable of stinging, the young scorpi
-
ons leave the mother after about 2 weeks and begin
to fend for themselves. Scorpions reach maturity in
a year or so, depending on the availability of food.
3
The stings from Texas scorpions produce only
moderate reactions in most people because the
poison has little effect on the nervous system. Sever
-
ity of the sting is dependent upon the individual
scorpion and the person’s reaction to the venom. A
person who is stung by a scorpion should be watched
closely for adverse reactions. As with any arthropod
venom, allergic reactions are possible. An ice pack
applied to the affected area will relieve some pain. If
swelling and/or pain persists or if breathing difficul
-
ties occur, immediate medical attention is necessary.
Scorpions as Pets
Scorpions have been kept as pets, but this prac
-
tice is generally discouraged. Scorpions should
never be kept indoors or around small children.
Scorpions with even relatively low poison levels can
produce fatal reactions in young children and also
in adults allergic to the toxin.
Management
Scorpions are difficult to control with insecti
-
cides alone. Therefore, the first control strategy is
to modify the area surrounding a structure.
•
Remove all trash, logs, boards, stones, bricks
and other objects from around the structure.
•
Keep grass closely mowed near the structure.
Prune bushes and overhanging tree branches
away from the structure. Tree branches can
give scorpions a path to the roof.
•
Store garbage containers in a frame that
keeps them above ground level.
•
Never bring firewood inside the structure
unless it is placed directly on the fire.
•
Install weather-stripping around loose-fit
-
ting doors and windows.
•
Plug weep holes in stone or brick veneer
structures with steel wool, copper mesh,
pieces of nylon scouring pad, or small
squares of screen wire. (Steel wool will rust
when wet, so it should be used only on dark-
colored facades.)
•
Use sealant around roof eaves, pipes, and
any other cracks into the structure.
•
Keep window screens in good repair. Make
sure they fit tightly in the window frame.
Naturally derived pesticides for managing scor
-
pions include active ingredients such as rosemary oil,
cinnamon oil, clove oil, thyme oil, peppermint oil,
and pyrethrum. Naturally derived products gener
-
ally degrade more quickly than synthetic pesticides
so they may not provide a long residual control.
Synthetic pesticides for scorpion control may
contain active ingredients such as permethrin, cyflu
-
thrin, cypermethrin, lambda-cyhalothrin, delta
-
methrin, propoxur, carbaryl or bifenthrin. Look for
products containing these active ingredients or con
-
sult a pest control operator.
Apply pesticides around the foundation of the
house and up to 1 foot above ground level on the
exterior walls. Also apply pesticides around doors,
window eaves, and other potential points of entry.
Indoor treatments should be directed at potential
points of entry, corners, cracks, and crevices where
scorpions hide. Follow directions on the package
for dosage, mixing, and application methods
.
.
Tips for Professionals
•
Wettable powder formulations of perimeter
sprays provide better residual control for
crawling pests because they leave an even
film of powder along the foundation after the
concrete has absorbed the water.
•
When using pyrethroids or other insecti
-
cides labeled for scorpion control, be sure to
use the highest permissible label rate.
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