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Smeringurus mesaensis

What do they look like?

Scorpions can be divided into the front portion, or cephalothorax and the back, the abdomen. The back of the cephalothorax is covered by a hard shell, or carapace. These scorpions have more than one pair of eyes, one pair of simple, median eyes on the front part of the carapace and lateral eyes on each side of the carapace. Scorpions have arm-like structures known as pedipalps that have large claws at the end, which is one of the most recognizable scorpion features. They have four pairs of legs. Their abdomen can be divided into the front part, or mesosoma, and the tail, or metasoma. The mesosoma has 7 segments, each covered by a hard plate. The metasoma has 5 segments, ending in the stinger. On their underside, near the middle of their body, they have comb-like sensory structures. Dune scorpions are a sandy beige color. They are so light that they may look almost see-through. Their hard plates are a darker brownish-grey, while their joints and part of their pedipalps may be darker. On average, dune scorpions are 72 mm long and weigh 2 g. Females are usually larger than males, although males have larger pedipalps and older males have longer comb-like pectines than females. (Hjelle, 1990; Polis and Farley, 1979; Polis and Sissom, 1990; Polis, 1980)

  • Sexual Dimorphism
  • female larger
  • Average mass
    2 g
    0.07 oz
  • Average length
    72 mm
    2.83 in

Where do they live?

Dune scorpions (Smeringurus mesaensis) are found in North America. They are a common scorpion species in the southwestern United States in the southern half of California and Arizona. They are also found in Mexico, especially in Baja California. (Haradon, 1983)

What kind of habitat do they need?

Dune scorpions live in open desert or dune habitats. They spend much of their time in the burrows they dig in the sand. (Haradon, 1983; Warburg and Polis, 1990)

How do they grow?

Dune scorpions fertilize their eggs while mating, after which the eggs develop inside the female for 10 to 14 months. These scorpions give birth to live young between July and September. After birth, young dune scorpions climb on their mother's back, until their first molt, which occurs about 12 days later. Juveniles then leave and have 6 more molts over the next 19 to 24 months. After their final molt, they reach adulthood. (Polis and Sissom, 1990)

How do they reproduce?

Mating takes place in August and September, usually on moonless nights. Dune scorpions have long courtship dances. During mating season, males become less predictable and spend more time on the surface, out of their burrows. They travel long distances, become skittish, and feed less. Females that are ready to breed can sense the vibrations made by nearby males. In this species, females also produce pheromones to attract mates and they start the mating process. A female finds a male and “attacks” him by quickly clubbing him with her tail, with the stinger tucked away. They both back away and the male “judders” by rocking back and forth with his legs and comb-like pectines spread out. Juddering may help females find males of the same species. The female attacks again and the pattern repeats, again and again, until the male grasps the female for the mating dance. His pedipalps grip her pedipalps, and he leads her in search of an area to release his spermatophore. This walk can last from 5 to 35 minutes, and the pair can move a few meters or as far as 25 meters. During this time, the male massages the female's chelicerae (mouth parts) with his own chelicerae. The female becomes more cooperative and less aggressive during the massage. The male's pectines are spread throughout this time, which likely helps sense chemicals. When the male finds a suitable spot, he scrapes the sand with his legs, maybe clearing a spot, and releases the spermatophore on a surface such as a stick. The spermatophore stands upright, and he pulls the female over it. She lowers herself and takes up the sperm. After a few seconds, sperm transfer is complete, and she does a “handstand”, by tilting forward. As soon as this is done, the male tries to leave, usually by stabbing the female with his stinger to try to make a quick getaway. Sometimes, he manages to run free, while the female stands and sways, which likely helps the sperm travel in her reproductive system. Other times, the female catches the male and stings and eats him. Males may massage the female's chelicerae to try to calm them, to avoid being eaten. If the male survives, he is able to mate again with other females. (Polis and Farley, 1979; Polis and Sissom, 1990; Warburg and Polis, 1990)

After mating, female dune scorpions carry fertilized eggs for 10 to 14 months before giving birth to live young between July and September. While giving birth, female dune scorpions usually hide in their burrows and lift their body, flexing their palps and legs to form a "birth basket". This species is born covered in a membrane and must wriggle free. When they are free, they climb up the female's legs and onto her back. They remain there until their first molt, in about two weeks. On average, they have a litter of about 33 young, but they can have anywhere from 9 to 53 young. Dune scorpions reach maturity in 19 to 24 months. Females of this species can produce up to two litters, each a year apart. (Polis and Sissom, 1990; Polis, 1980)

  • How often does reproduction occur?
    Dune scorpions have one litter per year.
  • Breeding season
    Mating takes place in August and September.
  • Range number of offspring
    9 to 53
  • Range gestation period
    10 to 14 months
  • Range age at sexual or reproductive maturity (female)
    19 to 24 months
  • Range age at sexual or reproductive maturity (male)
    19 to 24 months

Females give a great deal of parental care to their young. Before being born, the egg's yolk helps nourish the young. At birth, the female loses 43% of her body weight, which shows just how much they invest in their young. Once the young are born, they climb onto her back and stay there until their first molt, which happens about 12 days later. During this time, the young do not eat, but they do get water from their mother. This time spent with their mother is very important, as young scorpions that are taken away from their mother do not survive. After their first molt, the young leave, and the female stops caring for them. The female may even become predatory towards her young if they do not leave at this time. (Polis and Sissom, 1990)

  • Parental Investment
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
  • pre-weaning/fledging
    • protecting
      • female
  • pre-independence
    • protecting
      • female

How long do they live?

Dune scorpions live an average of 5 to 7 years. (Polis and Farley, 1979; Polis and Sissom, 1990)

  • Average lifespan
    Status: wild
    5 to 7 years

How do they behave?

Dune scorpions spend much of their time in the burrows they dig, up to 92 to 97% of their life. The burrow keeps them safe from predators and gives them a place to hide from the harsh extremes and dry conditions of the desert. Dune scorpions leave their burrows to hunt and mate. They are nocturnal and leave the burrow around dusk, spending an average of 4 hours on the surface. Adults are active earlier in the evening, while younger scorpions are active later in the evening. Dune scorpions are more active during mating season and when more prey are available. Males are especially active during mating season, moving large distances while searching for mates. Adults do not share their burrows, but young scorpions may stay together shortly after leaving their mother's burrow. Dune scorpions are very aggressive towards other scorpions and even eat other members of the same species. These scorpions are inactive during the winter. (McCormick and Polis, 1990; Polis and McCormick, 1987; Polis and Sissom, 1990; Polis, 1990; Warburg and Polis, 1990)

Home Range

Dune scorpions spend much of their time in burrows. At night, they come to the surface to hunt. These scorpions are very good at finding their home. They can travel up to 8 meters away from their burrow and find it again night. Because of this, they mostly stay in the same general area. However, during mating season, males are much more active, moving up to 100 meters each night. (Polis and Sissom, 1990; Polis, 1990)

How do they communicate with each other?

Dune scorpions get most of their information about their surroundings by sensing vibrations. They have sense organs and sensory hairs on their legs. These structures help them determine where the vibrations are coming from, whether the source is above or below ground. These scorpions are able to sense vibrations from up to 50 cm away. In response to a vibration, they quickly turn and face toward the direction of the source. This helps them find prey and mates. Females also use pheromones to attract mates. Pectines are comb-like structures found on their underside that act as chemical detectors. During the courtship dance, male's pectines are usually spread out and sweep across the ground. Throughout most of the courtship dance and mating, males and females keep a tactile (touch) connection, as the male holds onto the female and leads her, massaging her chelicerae. Dune scorpions have weak vision, they are nocturnal, but they can likely see stones and shadows at night, which allows them to travel several meters from their burrow and find their way back. Likewise, increasing amounts of light as morning approaches is a signal for scorpions to burrow for the day. (Brownell and Farley, 1979; Brownell, 2001; Hill, 2009; Hjelle, 1990; Polis and Sissom, 1990; Polis, 1990; Warburg and Polis, 1990)

What do they eat?

Dune scorpions are carnivorous and mostly eat insects and other arthropods. They may eat up to 125 different prey species. They are a sit and wait predator. They sit motionless in the mouth of their burrow, waiting for a prey item to move past. When they catch prey, they sting and paralyze the prey with their venom. They eat spiders, millipedes, centipedes, pillbugs, camel spiders, and a variety of insects. They may also eat smaller and younger members of their own species. Larger dune scorpions have been seen eating small snakes such as western slender blind snakes and they likely also eat other small reptiles. (McCormick and Polis, 1990; Polis, 1980; Warburg and Polis, 1990)

  • Animal Foods
  • reptiles
  • insects
  • terrestrial non-insect arthropods

What eats them and how do they avoid being eaten?

Predators of dune scorpions include small mammals such as grasshopper mice and birds including owls, as well as lizards, frogs, toads, snakes, arachnids, centipedes, and some insects, mainly ants. Dune scorpions are also often preyed on by other scorpion species and may also be eaten by members of the same species. To defend themselves, dune scorpions spend much of their time safely in their burrows. They also have a venomous sting, which may be used for defense, though it is mostly used to paralyze prey. Their thick, powerful pedipalps are mostly used for digging and can also be used to defend themselves. Young scorpions that have recently left their mother's care are most likely to be preyed on and gather together to appear larger and more threatening. (McCormick and Polis, 1990; Polis and Farley, 1979; Polis, 1980; Polis, 1990)

What roles do they have in the ecosystem?

Dune scorpions are often the most dominant scorpion species in the areas where it is found, with up to 1,300 to 4,000 dune scorpions per hectare. With so many scorpions in one area, they can be significant predators. Removing dune scorpions from an area often leads to other scorpion populations increasing. Dune scorpions are prey to a variety of desert animals including small mammals, birds, lizards, snakes, spiders, and other scorpions. They can also host mites. (McCormick and Polis, 1990; Polis and McCormick, 1987)

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host
  • mites (Pimeliaphilus joshuae)

Do they cause problems?

Dune scorpions are venomous, and use the venom in their tail to sting and paralyze prey. They may also sting to defend themselves. Dune scorpions have been known to sting humans when they feel threatened or disturbed. People who keep dune scorpions as pets should not handle them. Owners who have been stung by their scorpions describe it as similar to a hornet's sting. ("Smeringurus mesaensis care", 2008; McCormick and Polis, 1990)

  • Ways that these animals might be a problem for humans
  • injures humans

How do they interact with us?

Dune scorpions can be kept as pets. They should be kept in an enclosure like an aquarium, with something to burrow into, and can be fed insects. ("Smeringurus mesaensis care", 2008)

  • Ways that people benefit from these animals:
  • pet trade

Are they endangered?

Dune scorpions are not endangered.

Some more information...

Dune scorpions (Smeringurus mesaensis) are also known as Paruroctonus mesaensis. Their genus (Smeringurus) is relatively new. All scorpions including dune scorpions glow under UV light. This is an easy way to find them at night when they are active. (Brownell and Polis, 2001; Haradon, 1983)

Contributors

Angela Miner (author), Animal Diversity Web Staff, Leila Siciliano Martina (editor), Animal Diversity Web Staff.

References

2008. "Smeringurus mesaensis care" (On-line). ScorpionForum. Accessed January 03, 2014 at http://www.scorpion-forum.com/t911-smeringurus-mesaensis-care.

Brownell, P. 2001. Sensory Ecology and Orientational Behaviors. Pp. 159-183 in P Brownell, G Polis, eds. Scorpion Biology and Research. New York, New York: Oxford University Press.

Brownell, P., R. Farley. 1979. Detection of Vibrations in Sand by Tarsal Sense Organs of the Nocturnal Scorpion, Paruroctonus mesaensis. Journal of Comparative Physiology, 131: 23-30.

Brownell, P., G. Polis. 2001. Introduction. Pp. 3-12 in P Brownell, G Polis, eds. Scorpion Biology and Research. New York, New York: Oxford University Press.

Gefen, E. 2008. Sexual dimorphism in desiccation responses of the sand scorpion Smeringurus mesaensis (Vaejovidae). Journal of Insect Physiology, 54/5: 798-805.

Haradon, R. 1983. Smeringurus, a New Subgenus of Paruroctonus Werner (Scorpiones, Vaejovidae). Journal of Arachnology, 11/2: 251-270.

Hill, P. 2009. How do animals use substrate-borne vibrations as an information source?. Naturwissenschaften, 96/12: 1355-1371.

Hjelle, J. 1990. Anatomy and Morphology. Pp. 9-63 in G Polis, ed. The Biology of Scorpions. Stanford, California: Stanford University Press.

McCormick, S., G. Polis. 1990. Prey, Predators, and Parasites. Pp. 294-320 in G Polis, ed. The Biology of Scorpions. Stanford, California: Stanford University Press.

Polis, G. 1980. The effect of cannibalism on the demography and activity of a natural population of desert scorpions. Behavioral Ecology and Sociobiology, 7/1: 25-35.

Polis, G. 1990. Ecology. Pp. 247-293 in G Polis, ed. The Biology of Scorpions. Stanford, California: Stanford University Press.

Polis, G., R. Farley. 1979. Behavior and Ecology of Mating in the Cannibalistic Scorpion, Paruroctonus mesaensis Stahnke (Scorpionida: Vaejovidae). Journal of Arachnology, 7/1: 33-46.

Polis, G., S. McCormick. 1987. Intraguild Predation and Competition among Desert Scorpions. Ecology, 68/2: 332-343.

Polis, G., W. Sissom. 1990. Life History. Pp. 161-223 in G Polis, ed. The Biology of Scorpions. Stanford, California: Stanford University Press.

Warburg, M., G. Polis. 1990. Behavioral responses, rhythms, and activity patterns. Pp. 224-246 in G Polis, ed. The Biology of Scorpions. Stanford, California: Stanford University Press.

 
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Miner, A. 2014. "" (On-line), Animal Diversity Web. Accessed November 15, 2018 at http://www.biokids.umich.edu/accounts//

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