Animal Diversity Web

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.

• Biogeographic Regions
• nearctic
• oriental
• ethiopian
• neotropical
• australian

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.

• Habitat Regions
• temperate
• tropical
• terrestrial

• Terrestrial Biomes
• desert or dune
• savanna or grassland
• forest
• rainforest
• scrub forest

Systematic and Taxonomic History

Scorpionidae was first introduced by Pierre Andre Latreille in 1802 and included all scorpions. The family was first reduced reduced in 1837 and than in 1893 was divided into five the five subfamilies Scorpionini, Ischnurini, Diplocentrini, Hemiscorpiini and Urodacini. In 1905 Diplocentrini were removed to be classified as their own family and the subfmaily Heteroscorpionine was added to Scorpionidae until 1996 when they were also removed to be classified as their own family. (Fet 2000). A 2003 study suggested that the family Diplocentridae should be grouped together with Scorpionidae. There is still debate as to whether or not this is actually the case, as of 2017 was still a valid number of researchers who treat Diplocentridae as a valid family. (Fet, et al., 2000)

• Synonyms

  • Diplocentridae
  • Centurides
  • Pandinoidae
  • Heterometridae

• Synapomorphies

  • Pentagonal sternum
  • Broad pedipalps
  • Viviparous

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)

• Other Physical Features
• ectothermic
• bilateral symmetry
• venomous

• 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 System
• monogamous

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.

• Key Reproductive Features
• seasonal breeding
• sexual
• fertilization
  • external
• viviparous

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.

• Parental Investment
• precocial
• female parental care

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)

• Key Behaviors
• fossorial
• nocturnal
• motile
• sedentary
• solitary

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)

• Communication Channels
• tactile
• chemical

• Other Communication Modes
• vibrations

• Perception Channels
• tactile
• chemical

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.

• Known Predators

  • birds (Aves)
  • spiders (Araneae)
  • snakes (Lacertilia)
  • bats (Chiroptera)
  • centipedes (Chilopoda)

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)

• Positive Impacts
• pet trade
• source of medicine or drug
• controls pest population

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
  • bites or stings
  • venomous

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.

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.