Scorpionidae

Diversity

The family Scorpionidae, which consists of burrowing and pale-legged scorpions, includes 21 genera, 311 species, and four subfamilies. Morphologically, they are similar to other members of the order Scorpiones. The body consists of two main segments, the prosoma and the opisthosoma, with the prosoma being covered by a carapace. The most defining characteristics of species in this group are their powerful, broad pincers, which are modified pedipalps, and their segmented curved telson with a venomous stinger on the end. The family Scorpionidae includes the largest species of scorpion, Heterometrus swammerdami, the giant forest scorpion, which grows up to 23cm in length and weighs up to 56 grams. Scorpionidae also includes one of the most well known species, Pandinus imperator, or the emperor scorpion. Scorpions are nocturnal and mainly ambush predators. Their diet consists of a wide variety of prey including spiders, insects, smaller scorpions, lizards and small mammals. They are found in deserts, savannahs, humid forests and rain forests in Africa, Asia, Australia and North, Central and South America. (Fet, et al., 2000; Frantisek, 2016)

Geographic Range

Scorpions can be found in the tropical, subtropical, and warm temperate regions around the world.

Habitat

Scorpions can be found all over the world. They prefer deserts, savannas, humid forests, and rain forest. Many species live in burrows and prefer habitats with either sand or loose soil. Most of the daylight is spent either in their burrow or under rocks or logs. The constructed burrows can be up to a meter long and help to keep them cool during the day.

Physical Description

Scorpions are typically identified by a heavy body, broad pedipalps with short fingers, a short metasoma and short, stout legs (Harington 1977). Scorpions have a chitin exoskeleton which covers the prosoma and opisthosoma, the two main parts of the body, with a carapace covering the prosoma. Two centrally located eyes can be found on top of the carapace along with lateral eyes on the sides. Scorpions have both chelicerae, which are the appendages closest to the mouth and are used to pull small bits of food towards the mouth and pedipalps which are the claws used to capture and tear prey apart. The massive pincers and the pentagonal shaped sternum are the easiest way to distinguish the Scorpionidae from the sister taxa Buthidea. The opisthosoma is the posterior part of the body and consists of 13 segments which are separated into the mesosoma and metasoma. The mesosoma is the body and consists of seven segments while the metasoma is five segments which make up the tail and include a terminally located venomous stinger. Scorpionidae contains some of the world's largest living scorpions. Heterometrus (Gigantometrus) swammerdami reaches lengths up to 16.8cm , and Pandinus imperator, can measure between 18 and 20cm. A third species, Opistophthalmus gigas, has been recorded at 16cm in length. These characteristics represent both sister groups Scorpionidae and Diplocentridae. Both sexes are similar making it difficult to distinguish them. (Al-Asmari, et al., 2007)

  • Sexual Dimorphism
  • sexes alike

Reproduction

Mating involves three phases, with the first being the introductory phase. Courtship begins with the female’s pedipalps, chelae or other segments being gripped by the male’s pedipalps. After gripping, the female typically attempts to push the male away with her metasoma, often by trying to sting. Often times the male will use his own metasoma as a club in an attempt to protects itself from stinging (Jiao 2009). Once the grip is released, the female walks towards the male and starts to rock her body forward and back, with the male then repeating the motion. The female will then start to grab him using her own pedipalps. After the second grip the male will began his walk leading into the second phase which is known as the promenade phase. The male walks backwards with the female following. They then engage in a chelicerae grip and walk a short distance, during which the male will clear a spot for the spermatophore deposition. Once a suitable spot is found, the male swill lower its mesosoma in order to deposit the spermatophore. The male will then move his prosoma back and forth until the sticky basal plate makes contact with the surface of substrate (Jiao 2009). The male then pulls the female over the spermatophore in order to initiate sperm transfer. (Jiao and Zhu, 2009)

Mating is seasonal depending on the climate. Species in temperate regions mate during the summer or spring, and those in tropical regions mate during the rainy season. Seven to nine months after fertilization, females can give birth to up to 100 offspring. Unlike other arthropods, the young are born alive. The young will go through five different molts before they reach full development. Females are able to reproduce between a few months and one year since their last mating.

The young, which are born alive, are miniature versions of adults with less robust exoskeleton. After the young are born they crawl onto the backs of their mothers, where they remain until they have undergone their first molt, between 30 and 50 days, and their exoskeleton has become hard enough for them to survive on their own. In some cases, the mother will resort to cannibalism of her young if she is unable to find food.

Lifespan/Longevity

Lifespan varies by species but typically ranges between 5 to 8 years in captivity, and potentially longer in the wild

Behavior

Scorpion species are solitary and live in burrows. Only males leave the burrows for extended periods of time in order to find mates. It is believed that scorpions may uses senses other than hearing or sight in order to help locate prey (Polis 1986). The location of prey is determined by either the tarsal organs or by long thin sensory hairs on the pedipalps, known as trichobothria. The use of the venomous stinger depends on the maturity of the scorpion, with young stinging prey 2 to 3 times and adults using only their pedipalps. Scorpions are either sit and wait predators, where prey is located just outside the burrow or they are active hunters away from their burrow (McCormick 1990). (McCormick and Polis, 1986; Polis and McCormick, 1990)

Communication and Perception

Even with 2 large eyes on the top of their heads and up to five pairs on eyes on the sides of their carapace, scorpions still have poor eye sight. It has been shown that scorpions eyes are most sensitive to green and UV light. (Gaffin 2012). Hearing is done by picking up vibrations in the ground through the tarsal regions of their front legs. Because scorpions are solitary, there is little communication between individuals, but they can use pheromones to attract mates. (Gaffin, et al., 2012)

Food Habits

Scorpions eat small insects, arthropods, or small vertebrates such as mice or lizards. Juveniles use their venomous stinger to capture prey while adults use their pincers to crush and rip apart their prey. Usually the scorpion will grasp the prey at either end, thereby obtaining a head grip with one pedipalp that is frequently lethal when force is applied. Prey is often passed from pedipalp to pedipalp in order to find an the most effective grip (Casper 1985).

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
    • eats body fluids
    • insectivore
    • eats non-insect arthropods

Predation

The natural predators of scorpions include various birds, mammals, spiders, lizards, bats and centipedes. Defense against prey depends on what their strongest defense is. Scorpions with strong pincers will use their pincers while scorpions with strong venom will use their stinger.

Ecosystem Roles

Scorpions serve a vital role in the ecosystem eating small animals and are an important source of prey for larger animals. Areas with a high population of scorpions see them serve an important role in the food web by helping to control the insect population.

Economic Importance for Humans: Positive

The venom of different scorpions is used for various medical purposes. Scorpine is a peptide found in the venom of Pandinus imperator and is believed to have anti-malarial and anti-bacterial benefits. Scorpine is unique in that it is about double the size of other peptides. Scorpine is thought to be hybrid of the peptides cecropin and defensin, with some stretches of the sequence showing identical amino acids( Conde et al 2000). Pandinus imperator and members of the genus Heterometrus are popular in the pet trade due to their large size. (Conde, et al., 2000)

Economic Importance for Humans: Negative

The stings of most scorpions are fairly mild and are often compared to bee stings. Scorpions with deadly stings belong to the family Buthidae.

  • Negative Impacts
  • injures humans

Conservation Status

The species Pandinus imperator may be of conservation concern because of its popularity in the exotic pet trade. There are currently two members of the Buthidae family which are classified as endangered. Habitat destruction and the exotic pet trade are currently the two biggest threats to scorpions (Prendini et al. 2003. (Prendini, et al., 2003)

  • IUCN Red List [Link]
    Not Evaluated

Other Comments

In 2013 a 350 million year old scorpion fossil was found in South Africa and represents the oldest known land animal to live on the supercontinent Gondwana (Gess 2013). Scorpions glow a vivid-blue green color when under black light, the function of this fluorescence is a mystery. (Gess, 2013)

Contributors

Ryan Wood (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

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Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

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Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

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Neotropical

living in the southern part of the New World. In other words, Central and South America.

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bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

insectivore

An animal that eats mainly insects or spiders.

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

nocturnal

active during the night

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

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pet trade

the business of buying and selling animals for people to keep in their homes as pets.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

venomous

an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).

vibrations

movements of a hard surface that are produced by animals as signals to others

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial

young are relatively well-developed when born

References

Al-Asmari, A., A. Al-Saif, N. Abdo. 2007. Morphological identification of scorpion species from Jazan and Al-Medina Al-Munawara regions, Saudi Arabia. Journal of Venomous Animals and Toxins including Tropical Diseases, 13/4: 821-843.

Alexis, H. 1977. Burrowing Biology of the Scorpion Cheloctonus jonesii Pocock (Arachnida: Scorpionida: Scorpionidae). The Journal of Arachnology, 5/3: 243-249.

Casper, G. 1985. Prey capture and stinging behavior in the Emperor Scorpion, Pandinus Imperator (koch) (scorpiones, scorpionidae). The Journal of Arachnology, 13: 277-283.

Conde, R., F. Zamudio, M. Rodriguez, L. Possani. 2000. Scorpine, an anti-malaria and anti-bacterial agent purified from scorpion venom. FEBS Letters, 471, 2-3: 165-168.

Fet, V. 2005. Contributions to scorpion systematics. I. On recent changes in high-level taxonomy. Euscorpius, 31: 1-13.

Fet, V., W. Sissom, G. Lowe, M. Braunwalder. 2000. Catalog of the scorpions of the world (1758-1998). New York: New York Entomological Society.

Frantisek, K. 2009. Illustrated catalog of scorpions. Part I. Introductory remarks; keys to families and genera; subfamily Scorpioninae with keys to Heterometrus and Pandinus species. Prague: Clairon Production.

Frantisek, K. 2016. Scorpions of the Horn of Africa (Arachnida: Scorpiones). Part VIII. Pandinops Birula, 1913 (Scorpionidae), with description of two new species. Euscorpius, 229: 1-20.

Gaffin, D., L. Bumm, M. Taylor, N. Popokina, S. Mann. 2012. Scorpion fluorescence and reaction to light. Animal Behaviour, 83/2: 429-436.

Gess, R. 2013. The Earliest Record of Terrestrial Animals in Gondwana: A Scorpion from the Famennian (Late Devonian) Witpoort Formation of South Africa. African Invertebrates, 54(2): 373-379.

Jana, P., K. Frantisek, K. Ondrej, S. Frantisek. 2016. DESCRIPTION OF A NEW SPECIES OF HETEROMETRUS EHRENBERG, 1828 (SCORPIONES: SCORPIONIDAE) FROM THAILAND WITH REMARKS ABOUT THE UTILIZATION OF CYTOGENETIC DATA IN TAXONOMY OF THE GENUS. Annales Zoologici (Warsaw), 66 3: 467-476.

Jiao, G., M. Zhu. 2009. Courtship and Mating in Heterometrus petersii (Thorell, 1876) (Scorpiones: Scorpionidae). Euscorpius - Occasional Publications in Scorpiology, 84: 1-5.

McCormick, S., G. Polis. 1986. Patterns of resource use and age structure among species of desert scorpion. Journal of Animal Ecology, 55: 59-73.

Newlands, G. 1980. A revision of the scorpion genus Hadogenes Kraepelin 1894 (Arachnida: Scorpionidae) with a checklist and key to the species. Potchefstroom: Potchefstroom University.

Polis, G., S. McCormick. 1990. The Biology of Scorpions. Palo Alto, CA: Stanford University Press.

Prendini, L. 2016. Redefinition and systematic revision of the East African scorpion genus Pandinoides (scorpiones: scorpionidae) with critique of the taxonomy of Pandinus, Sensu Lato. Bulletin of the American Museum of Natural History, 407: 1-66.

Prendini, L., W. Wheeler, T. Crowe. 2003. Systematics and biogeography of the family Scorpionidae (Chelicerata:Scorpiones), with a discussion on phylogenetic methods. Invertebrate Systematics, 17: 185-259.

Prendini, L., W. Wheeler. 2005. Scorpion higher phylogeny and classification, taxonomic anarchy, and standards for peer review in online publishing. Cladistics, 21 5: 446-494.

Santibáñez-López, C., R. Kriebel, . Sharma. 2017. adem figura manet: Measuring morphological convergence in diplocentrid scorpions (Arachnida : Scorpiones : Diplocentridae) under a multilocus phylogenetic framework. Invertebrate Systematics, 31: 233-248.

Soleglad, M., v. Fet. 2003. High-level systematics and phylogeny of the extant scorpions (Scorpiones: Orthosterni). Euscorpius, 11: 1-56.

Stay, T., I. Tesler, J. Sivan, R. Ben-Shlomo, T. Muhammad. 2015. Scorpion speciation in the Holy Land: Multilocus phylogeography corroborates diagnostic differences in morphology and burrowing behavior among Scorpio subspecies and justifies recognition as phylogenetic, ecological and biological species. Molecular Phylogenetics and Evolution, 91: 226-237.

Teruel, R., T. Rodriguez-Cabrera. 2017. The missing piece of the puzzle solved: Heteronebo Pocock, 1899 (Scorpiones: Scorpionidae) occurs at Isla de Pinos, Cuba. Euscorpius, 240: 1-4.