Scorpions

L-16784-00

J. A. Jackman*

S corpions are arachnids, close relatives ofticks, mites and spiders. They are easily recognized by their characteristic shape.

Scorpions prefer dryland habitats but they dooccur throughout Texas. They can be a nuisancewhen they interact with humans because theywill sting when disturbed.

DescriptionScorpions have a long, slender body with a

five-segmented tail that can be arched over theback. The tail ends in a bulb-like poison gland orstinger. Scorpions have four pairs of legs and twolarge pincer-bearing arms (pedipalps) in front.Scorpions are well equipped to defend them-selves or attack prey with their pincers andstinger. Between the last pair of legs is a comb-like structure (pectines) that is used to identifysurface textures and to detect prey.

Scorpions have two eyes on the top of thehead, and usually two to five pairs of eyes alongthe front corners of the head. They do not seewell, however, and must rely on the sense oftouch, using their pectines and other organs fornavigation and detecting prey. They also have awell-developed sense of hearing.

Worldwide, scorpions range in size from 1/2inch to 7 1/4 inches long (including the tail)depending on the species. The most commonspecies in Texas is the striped bark scorpion,Centruroides vittatus. The adult of this species isabout 2 1/2 inches long, typical of the size of allspecies found in the state.

Biology Scorpions hide during the day and become

active at night. This behavior helps scorpionsmanage temperature and water balance, impor-tant functions for survival in dry habitats. Manyspecies dig burrows in the soil. Their bodies areflat, which allows them to hide in small cracks,and under stones, bark, wood or other objects onthe ground. From these hiding places they waitor search for prey. Chief foods are small insects,spiders, centipedes, earthworms and other scor-pions. Once they capture their prey, they use thelarge pincers to crush and draw it toward themouth so the prey’s body juices can be eaten.

Some species may live for 20 to 25 years, butlongevity of the typical scorpion is between 3and 8 years.

*Professor and Extension Entomologist, The Texas A&M UniversitySystem.

Pincer

Walking legs

Stinger

Tail}

}Pedipalp

Dorsal view of a scorpion.

Adult scorpions may have several broods ofyoung. Following an elaborate mating process,which lasts from 24 to 36 hours, the femaleundergoes a gestation period ranging from 5months to more than 1 year. The young are bornalive in semitransparent sacs. As soon as theyoung scorpions free themselves from these thinwrappers, they climb onto their mother’s back.Already capable of stinging, the young scorpionsleave the mother after several days and begin tofend for themselves. Scorpions reach maturity ina year or more, depending on the availability offood.

The sting of scorpions may be painful, or evendeadly, depending on the species. Of 1,500species of scorpions worldwide, only about 20 to25 are regarded as dangerous. Stings from suchspecies may cause paralysis, severe convulsions,cardiac irregularities, or breathing difficultiesthat may lead to death. Antivenins are availablein areas where dangerous scorpions live.

A scorpion’s venom is a mixture of com-pounds including neurotoxins that affect the vic-tim’s nervous system. Fortunately, none of thespecies in Texas are considered deadly. Stingsfrom most of these species are about as painfulas a bee or wasp sting, but the severity of thesting is dependent upon the individual scorpionand the person’s reaction to the venom. As withany arthropod venom, allergic reactions are pos-sible. In these situations, immediate medicalattention would be required.

HabitatScorpions are found in many types of habitats

in the United States, including desert flats, sanddunes, desert and mesic mountains, grasslands,pine forests, deciduous forests and chaparral.Species are most diverse in desert areas.

Ta xonomic StatusAbout 90 species of scorpions have been iden-

tified in the United States. Texas has 18 species,but only one species, Centruroides vittatus, occursthroughout the state. It is the only species ofscorpion found in the eastern part of Texas. Westand South Texas have the largest number ofspecies. One species has been recorded in theDallas area, two recorded near Austin, four nearAmarillo, three near Abilene, five near FortStockton, eight in the Fort Davis region, eightnear Langtry, and 14 in Big Bend National Park.

S triped Bark ScorpionThe striped bark scorpion is by far the most

common scorpion in Texas and the most likely tobe encountered by humans. It has two broad,black stripes running the length of its back.Populations in the Big Bend may be only faintlymarked or completely pale. The basic color ofthe scorpion varies from yellow to tan in adults.Immature scorpions may be lighter in color.There is a dark triangular mark on the front ofthe head above the eyes. In young scorpions, thebase of the pedipalps and the last segmentbehind the abdomen are dark brown or black.This species can be easily identified by slenderpedipalps (pincer-bearing arms) and the long,slender tail. The tail is longer on males thanfemales.

The striped bark scorpion apparently mates inthe fall, spring or early summer. Gestationrequires about 8 months. Litter size varies from13 to 47. The average is about 31 young per lit-ter.

Immature scorpions molt within 3 to 7 daysafter birth and remain on the mother for another3 to 7 days after that. There are five or six moltsto maturity. A striped bark scorpion probablylives for approximately 4 years.

The sting of this species causes local pain andswelling. Deaths attributed to this species havenot been substantiated.

The striped bark scorpion is often found underrocks, under boards and in debris. It can befound indoors or outdoors in a wide variety ofhabitats (pine forests in East Texas; rocky slopes,grasslands and juniper breaks in other parts ofthe state). Centruroides are active foragers that donot burrow. They are distinctly associated withdead vegetation, fallen logs and humandwellings. It is common for them to climb treesand walls, and they often are found in the atticsof homes. During periods of hot weather, scorpi-ons may move into living areas to escape thehigh temperatures in attics.

Scorpion StingsWhen handled or disturbed, scorpions can

inflict a painful sting using the poison gland atthe end of the tail. Avoiding their habitats helpsprevent stings. The stings from Texas scorpionsproduce only moderate reactions in most peoplebecause the poison has little effect on the ner-vous system. However, a person who is stung bya scorpion should be watched closely for adverse

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reactions. An ice pack applied to the affectedarea will relieve some pain. If swelling and/orpain persists or if breathing difficulties occur,immediate medical attention is necessary.

Scorpions as PetsScorpions have been kept as pets, but this

practice is strongly discouraged. Scorpionsshould never be kept indoors or around smallchildren. Scorpions with even relatively low poi-son levels can produce fatal reactions in youngchildren and also in adults allergic to the toxin.

Co ntro lScorpions are difficult to control with insecti-

cides alone. Therefore, the first control strategyis to modify the area surrounding a house.

■ Remove all trash, logs, boards, stones, bricksand other objects from around the home.

■ Keep grass closely mowed near the home.Prune bushes and overhanging tree branch-es away from the house. Tree branches canprovide a path to the roof for scorpions.

■ Store garbage containers in a frame thatallows them to rest above ground level.

■ Never bring firewood inside the houseunless it is placed directly on the fire.

■ Install weather-stripping around loose fittingdoors and windows.

■ Plug weep holes in brick veneer homes withsteel wool, pieces of nylon scouring pad orsmall squares of screen wire.

■ Caulk around roof eaves, pipes and anyother cracks into the home.

■ Keep window screens in good repair. Makesure they fit tightly in the window frame.

To control scorpions with chemicals, use insec-ticide products that contain any of the following:

■ permethrin (Prelude®, Dragnet®);■ cyfluthrin (Tempo®);■ cypermethrin (Demon®);■ lambda-cyhalothrin (Demand CS®);■ deltamethrin (Suspend®);■ propoxur (Baygon®);■ diazinon;

■ chlorpyrifos (Dursban®);■ malathion;■ synergized pyrethrins.Apply pesticides around the foundation of the

house and up to 1 foot above ground level on theexterior walls. Also apply pesticides arounddoors, window eaves and other potential pointsof entry. Follow directions on the package fordosage, mixing and application methods.

Tips for Pro fessionals■ Wettable powder formulations provide bet-

ter residual control for crawling pests whenapplying perimeter sprays.

■ When using pyrethroids or other insecti-cides labeled for scorpion control, be sure touse the highest permissible label rate.

Policy State m e nt for MakingChemical Co ntrol Suggestions

Suggestions on pesticide use made by theTexas Agricultural Extension Service and theTexas Agricultural Experiment Station are basedupon:

■ effectiveness under Texas conditions,■ avoidance of residues in excess of allowable

tolerances,■ avoidance of toxicity to desirable vegetation,

animals and humans, and■ avoidance of adverse side effects upon bene-

ficial predators, parasites, honeybees, fishand other wildlife, plants, animals andhumans.

Suggested pesticides must be registered andlabeled for use by the Environmental ProtectionAgency and the Texas Department of Agriculture.The status of pesticide label clearances is subjectto change and may have changed since this pub-lication was printed. County Extension agentsand appropriate specialists are advised ofchanges as they occur.

The USER is always responsible for the effectsof pesticide residues on his/her livestock andcrops, as well as problems that could arise fromdrift or movement of the pesticide from his/herproperty to that of others.

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Educational programs of the Texas Agricultural Extension Service are open to all people without regard to race, color, sex, disability, religion, ageor national origin.Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, andJune 30, 1914, in cooperation with the United States Department of Agriculture. Chester P. Fehlis, Deputy Director, Texas Agricultural ExtensionService, The Texas A&M University System.5M, Revision ENT

Produced by Agricultural Communications, The Texas A&M University SystemExtension publications can be found on the Web at: http://texaserc.tamu.edu

Acknowledgment The previous edition of this manuscript was prepared by J. W. Stewart,former Extension entomologist, and forms the core of this version.

The information given herein is for educational purposes only. Reference to trade names is made withthe understanding that no discrimination is intended and no endorsement by the Cooperative ExtensionService is implied.