Scorpions are known as predatory arachnids of the order Scorpiones. They have eight legs and are easily recognized by the pair of grasping pedipalps and the narrow, segmented tail, often carried in a characteristic forward curve over the back, ending with a venomous stinger. Scorpions have adapted a wide range of environmental conditions and can be found all over the world, except for Antarctica. They are closely related to spiders, mites, and ticks. In total, a number of 1750 is known to exist, with only 25 know species that have venom capable of killing a human being. Stings caused by scorpions which are not venomous are harmless to humans. For stings from species found in North America, no treatment is normally needed for healthy adults, although medical care should be sought for children and for the elderly. More harmful stings from species found in South America, Africa, and western Asia may require medical attention.
Description and distribution of scorpions
Scorpions are easily recognizable with the help of 2 characteristics: the two pedipalps, an exaggerated pair of claws; and the narrow, segmented tail, which is most often carried in a forward curve over the back and which ends with a venomous stinger. A scorpion’s body is also covered in a strong, durable, yet still flexible exoskeleton, made out of chitin. It provides protection, aids scorpions in respiration, as well as stops water loss, which is critical in the case of those species that live in arid environments. Depending on the specie, scorpions range in size from 9 mm / 0.3 in. (Typhlochactas mitchelli) to 23 cm / 9 in. (Heterometrus swammerdami).
The body of the scorpion is divided into 2 main segments: the head (the cephalothorax or the prosoma) and the abdomen (the opisthosoma), which is subdivided itself into: the preabdomen (mesosoma) and the postabdomen or the tail (the metasoma).
The prosoma includes the eyes, the mouthparts (the chelicerae), the pedipals, the carapace, as well as 4 pairs of legs. Scorpions have 2 eyes on top of the head, and 2 – 5 (depending on the species) pairs of eyes along the front corners of the head. Despite this, however, scorpions are not able to see very well, although the sensitivity of their eyes is among the highest in all arthropods. The pedipalps are segmented appendages, which end in claws and are used to immobilize prey, to defend the individual, and to sense out the environment, as they are not used legs.
The mesosoma is made out of 7 segments. The first segment bears the reproductive organs and the second segment bears the sensory organs, while segments three to seven carry the respiratory organs. The abdomen is also the place where the 4 pairs of clawed legs are attached. The scorpion thus moves with the help of sensory structures in these 8 legs; these are pectines and fine sensory hairs, which detect vibrations.
The metasoma is made out of 5 segments, plus the sting (the telson), which is, in turn, comprised out of a vesicle (which holds the venom glands) and a hypodermic aculeus (which injects the venom). Some scorpions can be born with two tails, but this is rare, and it is a genetic abnormality, not a different species as some would think.
Scorpions species present a variety of colors that allow them to blend in with the surrounding areas. They can be black, brown, or even have a green tint. When exposed to certain wavelengths of ultraviolet light, scorpions are known to glow a vibrant blue-green, due to the presence of fluorescent chemicals in the cuticle.
As it comes to the distribution of scorpions around the world, they can be found on all major land masses except Antarctica. They were previously missing from Great Britain, Japan, South Korea, New Zealand and some of the islands in Oceania, but now have been accidentally introduced in some of these places by human trade and commerce. In the Northern Hemisphere is where they can be found in their greatest diversity, as they prefer the subtropical areas between latitudes 23° N and 38° N. they can be found in areas such as every terrestrial habitat, including high-elevation mountains, caves, or they can be may be ground-dwelling, tree-living, lithophilic (rock-loving) or psammophilic (sand-loving). Scorpions prefer areas where the temperatures range from 20 to 37 °C (68 to 99 °F), but may survive temperatures ranging from well below freezing to desert heat. They are nocturnal and diggers, finding shelter during the day in the relative cool of underground holes or undersides of rocks, and emerging at night to hunt and feed. Scorpions exhibit photophobic behavior, which means they stay out of the light, primarily to evade detection by predators such as birds, centipedes, lizards, mice, opossums, and rats.
Breeding and dietary information
Most scorpion species have both female and male individual, reproducing sexually. This occurs through the transfer of a spermatophore from the male to the female, a transfer preceded by various courtship and mating rituals. The male deposits the spermatophore in a suitable location, and then guides the female over it. This allows the spermatophore to enter her genital opercula, and once the sperm is released, the female is fertilized. This entire process can last from 1 to 25 hours, most of the time being spent on the male finding a suitable place to deposit the spermatophore before beginning the rituals of mating.
Other species, however (Hottentotta hottentotta, Hottentotta caboverdensis, Liocheles australasiae, Tityus columbianus, Tityus metuendus, Tityus serrulatus, Tityus stigmurus, Tityus trivittatus, Tityus urugayensis, etc.), reproduce through partheongenesis. This is a form of asexual reproduction, in which the growth and the development of the embryos occur without fertilization.
The number of offsprings can range between 2 – 100, depending mainly on the species, as well as environmental conditions. On average, though, a litter will count around 8 scorpions. Researchers have had trouble determining the general lifespan of scorpions, mainly due to the fact that they are very difficult to track. Therefore, all that is known is that scorpions can live anywhere between 6 months and 25 years.
Unlike the majority of species in the class Arachnida, which are oviparous, scorpions are ovoviviparous. This means that the younglings are born, one by one, only once they have hatched inside their mother. They have the appearance of small adults, except they are white, soft-bodied, and unable to sting or feed. Therefore, the younglings are then carried on the female’s back until they have undergone at least one molt, as they are unable to survive by themselves until then. Following this, they will usually disperse, but in some species, they remain close to the female for as long as 2 years. Development is accompanied by periodic sheddings of their exoskeleton. Typically, 5 – 7 molts are required to reach maturity, which occurs in 2 – 3 years, with exceptions in some species, in which reaching maturity can last from 6 months, up to 7 years.
Scorpions are opportunistic predators that mainly eat small arthropods, although large species also consume lizards and mice. They hunt with the help of their pincers and tail, although actual hunting techniques vary. Some species may wait, half hidden in their burrow, for the prey to wander into the range of their pincers. Pincers are lined with very sensitive tactile hairs; when the prey touches them, the pincers automatically contract, catching it. Others actively forage for prey, and others still, dig so-called traps (pitfalls in the sand). Depending on the species, and characteristics such as the toxicity of the venom and the size of the claws, scorpions will then inject the prey with venom or simply crush it.
Interestingly enough, scorpions have external digestion. Due to this ability of storing food before actually consuming it, scorpions can eat a very large amount of food in one sitting. They usually hunt once every 2 – 3 weeks, but they can survive long periods of time, up to 6 – 12 months, without food. When food is scarce, scorpions can also slow down their metabolism to as little as one third of its typical rate, thus consuming less oxygen and being able to live on as little as one insect per year.
Scorpions as pests
Scorpions do also play an important role in the ecosystem they are part of, by keeping insect populations low. In some parts of the world, scorpions are consumed, as in some parts of China, fried scorpion is a traditional dish. Scorpion venom is also used in medicine in South Asia, especially in antidotes. It is also used in the more modern pharmaceutical industry, especially n dermatology.
However, they are also known as common household pests, typically in the southern United States, specifically in desert regions. They typically do not leave signs, other than visual sightings of themselves. They usually become an indoor pest problem when they choose to leave their outdoor habitats in search of a better place to live where more food sources can be found. Scorpions do not go out of their way to sting people. Their natural inclination is to flee or give a threat display when disturbed. If a sting occurs, it usually is the result of the scorpion being crushed to the skin. This can happen when putting on gloves or shoes that a scorpion has taken refuge inside.
In order to prevent a scorpion sting, one should always follow the below steps:
- Wearing long sleeves and pants
- Wearing leather gloves
- Shaking your clothing or shoes before putting them on.
- People with a history of severe allergic reactions to insect bites or stings should consider carrying an epinephrine auto injector (EpiPen) and should wear a medical identification bracelet or necklace stating their allergy.
All scorpion species possess venom, although in different quantities and levels of toxicity. Their venom is a mix of compounds and is thought to be adapted to the individual’s lifestyle. As such, each of these compounds cause a different effect and is believed to possibly be targeted towards a specific animal (crustaceans, vertebrates, etc.), either due to hunting or as a means of protection. When injected, the venom attacks the nerve cells of the victim, causing paralysis. Generally fast-acting, it is used primarily to kill or paralyze prey, but also to defend against predators. Scorpions use venom in moderation, seeing as it takes a lot of time and energy to produce it. As mentioned before, only 25 species have venom that is strong enough to kill humans. There are also some animals (some of which are predators of scorpions) that are resistant or immune to scorpion venom, such as meerkats and mongooses, and the scorpion itself is resistant to its own venom.
In case you are dealing with a scorpions, or you just want to prevent an infestation, make sure you are controlling other pests roaming in your house or yard, as the first important step in getting rid of your scorpion problem, is by getting rid of their source food. More details about preventing a scorpion infestation and can be found in our relevant article.