scorpion

A scorpion is an invertebrate animal with eight legs, belonging to the order Scorpiones in the class Arachnida.

Physical characteristics

The scorpion body is divided into two segments: the cephalothorax (also called the prosoma) and the abdomen/opisthosoma.

Cephalothorax/prosoma: the scorpion's “head”, comprising the carapace, eyes, chelicerae (mouth parts), pedipalps (claw) and the four pairs of walking legs.

Metasoma: the scorpion's tail, comprising six segments (the first tail segment looks like a last mesosoman segment), the last containing the scorpion's anus and bearing the telson (the sting). Newly molted scorpions do not glow until after their cuticle has hardened.

Main physical features

Pedipalps: the long front appendages that end in the so-called "claws" (the correct term is chelae or "pincers"). The pedipalps are used primarily for prey capture but also play an important part in the scorpion mating dance. however, a general trend is that the more venomous the scorpion, the narrower the pincers, as scorpions with less potent venom use their larger pincers to subdue prey.

Pectines: these are a pair of feather-like sensory organs, consisting of a row of pegs, and are unique in scorpions. The pectines are located beneath the scorpion, attached to the sternum. They constantly touch the ground and play an important role in the scorpion's sensory equipment. The pectines are covered in thousands of chemosensors that allow the scorpion to detect minute chemical signals in their environment;

Eyes: fossil scorpions had compound eyes, modern scorpions in general have three sets of eyes. Some species of cave- and litter-dwelling scorpions, however, have no eyes, relying purely on their other senses. some have theorised that they even allow the scorpion to navigate by star light and help regulate the scorpion's circadian rhythm.

Two tails

On rare occasions, scorpions can be born with two metasoma (tails). Two-tailed scorpions are not a species, but rather a genetic abnormality..

Scorpion venom

All scorpion species possess venom. In general, scorpion venom is described as neurotoxic in nature. Scorpions use their venom to kill or paralyze their prey so that it can be eaten;

Scorpion venoms are optimized for action upon other arthropods and therefore most scorpions are relatively harmless to humans; A few scorpion species, however, mostly in the family Buthidae, can be dangerous to humans. The amount of venom typically injected by Androctonus australis, or fat-tailed scorpion of North Africa, results in this scorpion being the most deadly, but its toxicity is roughly half that of Leiurus quinquestriatus, which results in fewer deaths. These scorpions, and others in the family Buthidae, have been responsible for many human deaths. Scorpions are generally unable to deliver enough venom to kill healthy adults; One symptom of a scorpion sting can include numbing at the injection site, sometimes lasting for several days. Unless provoked, scorpions are generally harmless and timid and use their sting only for killing prey.

It is unknown whether scorpions are venom conservers; Many scorpion species, such as Pandinus and Hadogenes, rarely if ever use their venom, instead relying on their strong bulky pedipalps in prey capture.

Reproduction

Scorpions reproduce sexually and all species have male and female individuals. scorpions possess a complex courtship and mating ritual to effect this transfer.

Mating starts with the male and female locating and identifying each other using a mixture of pheromones and vibrational communication;

The courtship starts with the male grasping the female’s pedipalps with his own;

When he has identified a suitable location, he deposits the spermatophore and then guides the female over it.

Once the mating is complete, the male and female quickly separate. The male will generally retreat quickly, most likely to avoid being cannibalised by the female, although sexual cannibalism is infrequent with scorpions.

Birth and development

Unlike the majority of Arachnida, scorpions are viviparous.

The young resemble their parents in a general way. A scorpion's developmental progress is measured in instars (how many moults it has undergone). Generally, scorpions require between five and seven moults to reach maturity. The scorpion then emerges from this split; When it emerges, the scorpion’s new exoskeleton is soft, making the scorpion highly vulnerable to attack. The scorpion must constantly stretch while the new exoskeleton hardens to ensure that it can move when the hardening is complete.

Scorpions have very variable lifespans and the actual lifespan of most species is not known;

Origins

Scorpion remains are often found in coal deposits that are believed to be of the Carboniferous Period, and no essential structural difference has been discovered between these fossils (such as Palaeophonus, Pulmonoscorpius and Paraisobuthus) and existing forms — suggesting that the group has existed without material structural modification for about 300 million years.

The eurypterids, marine creatures who lived during the Paleozoic era, share several physical traits with the scorpion and are closely related to it. Despite this, some refer to them as "sea scorpions" .

Geographical distribution

Scorpions are almost universally distributed south of 49 ° N and their geographical distribution shows in many particulars a close and interesting correspondence with that of the mammals, including their entire absence from New Zealand.

In conformity with their wide dispersal, scorpions have become adapted to diverse conditions of existence, some thriving in rainforests, others on open plains, others in sandy deserts and a few even at high altitudes where the ground is covered with snow throughout the winter.

In the United States, scorpions are most common in southern Arizona and in a swath extending through central Texas and central Oklahoma. The common striped scorpion, Centruroides vittatus, reaches from northwest Mexico to southern Colorado, Kansas, southern Missouri and Mississippi. Scorpions can be found in 31 different states in the U.S., including Hawaii (Isometrus maculatus).

Five colonies of scorpions (Euscorpius flavicaudis) have established themselves in southern England having probably arrived with imported fruit from Africa, but the number of colonies could be lower now because of the destruction of their habitats. This scorpion species is small and completely harmless to humans.

Sahara Scorpion:

The arthropod most commonly associated with deserts, scorpions in the Sahara come in 30 different varieties, most from the family Buthidae. Four of the Sahara's scorpion species are lethal to humans. In some species, the scorpion's venom is as toxic as that of a cobra. The scorpion limits its activities to the night, burrowing into the cooler sands beneath the desert's surface during the day.

How scorpions eat

Scorpions generally use their chela (pincers) to catch the prey initially. This will kill or paralyze the prey so the scorpion can eat it. Scorpions have a quite unique style of eating which uses chelicerae. Scorpions can only digest food in a liquid form; any solid matter (fur, exoskeleton, etc) is disposed of by the scorpion.

Suicide misconception

The belief that scorpions commit suicide by stinging themselves to death when surrounded by fire is of considerable antiquity and is often prevalent where these animals exist. It is nevertheless untrue since the venom has no effect on the scorpion itself, nor on any member of the same species (unless the venom is injected directly into the scorpion's nerve ganglion). The misconception may derive from the fact that scorpions are poikilotherms: when exposed to intense heat their metabolic processes malfunction. This causes the scorpion to spasm wildly and this spasming may appear as if the scorpion is stinging itself. It is also untrue that alcohol will cause scorpions to sting themselves to death.

Radiation

It is said that scorpions can survive the radiation that results from the detonation of nuclear weapons. Indeed, scorpions have been observed surviving the radiation from nuclear weapons tests at French test sites in the Sahara . Scorpions are also known to glow when exposed to certain types of ultraviolet light such as that which is produced by a blacklight.

Classification

This classification is based on that of Soleglad &

Parvorder Pseudochactida Soleglad et Fet, 2003

Superfamily Pseudochactoidea Gromov, 1998

Parvorder Buthida Soleglad et Fet, 2003

Superfamily Buthoidea C. Koch, 1837 (thick-tailed scorpions) Family Microcharmidae Lourenço, 1996

Parvorder Chaerilida Soleglad et Fet, 2003

Superfamily Chaeriloidea Pocock, 1893

Superfamily Chactoidea Pocock, 1893

Superfamily Iuroidea Thorell, 1876

Superfamily Scorpionoidea Latreille, 1802

Cultural symbolism

The scorpion has had various meanings and representations in different cultures in history.

In Mesopotamia, Gilgamesh for example approaches mountains where scorpion folk guard the entrance.

In Egyptian mythology, the scorpion stands for Set, the Trickster and brother of Nephthys, nemesis and opponent of Osiris, and Isis.

The Falaknuma palace of Hyderabad, India, is laid out in the shape of a scorpion with two stingers spreading out as wings to the north.

Other use

From a Biblical quotation, it is the term for a severe Roman scourge.

Pest control

Scorpions are difficult to control with pesticides alone. Tree branches can provide a path to the roof for scorpions. When using pyrethroids or other insecticides labeled for scorpion control, be sure to use the highest permissible label rate.