10 Striking Facts About Scorpions

These ancient arachnids are as fascinating as they are frightening.

scorpion in sand
Scorpions may be the oldest terrestrial animals still living.

Chris Parker / Flickr/ CC BY-ND 2.0 

It's sensible to be afraid of scorpions. Their most distinctive features are pincer-like pedipalps and a stinging tail, which some species can swing toward their target at 50 inches (130 centimeters) per second.

That doesn't mean we have to hate them, though. Learning more about scorpions reveals them to be generally less dangerous than they look, and it can also help us appreciate them as interesting and important members of our ecosystems.

1. Scorpions Were Around Long Before the First Dinosaurs

A fossil of a Eurypterid, or sea scorpion, from the Silurian Period.
A fossil of a Eurypterid, or sea scorpion, from the Silurian Period. Schafer & Hill / Getty Images

Scorpions may be the oldest land animals still living today. The fossil record suggests ancient scorpions were among the first marine animals to venture onto dry land, which happened about 420 million years ago, during the Silurian Period. For comparison, the earliest-known dinosaurs evolved about 240 million years ago. And modern humans only date back about 200,000 years, which means we're roughly 2,100 times younger than scorpions.

2. They Are Not Insects

Scorpions are arachnids, like spiders, mites, and ticks. As arachnids, they are part of a broader group of arthropods called chelicerates, which also includes horseshoe crabs and sea spiders. Importantly, chelicerates are not insects. Insects are a different type of arthropod. Chelicerates and insects can be distinguished in several ways, such as their number of legs: Adult insects have six legs, whereas arachnids and other chelicerates have eight legs plus two more pairs of appendages called the chelicerae and pedipalps. Chelicerae often take the form of mouthparts, and in scorpions, the pedipalps have evolved into pincers.

About 450 million years ago, some sea scorpions may have measured more than 3 feet (1 meter) long. Today, the largest species of extant scorpion is often said to be Asia's giant forest scorpion, which grows up to 9 inches (23 cm) long and can weigh 2 ounces (56 grams).

3. They Dance Before Mating

A pair of common yellow scorpions (Buthus occitanus) engage in a mating dance.
A pair of common yellow scorpions (Buthus occitanus) engage in a mating dance. Paul Starosta / Getty Images

Scorpions perform a courtship ritual that resembles a dance, sometimes known as a promenade à deux (French for "walk for two"). The details vary by species, but if the female shows interest in the male, they typically begin by facing off and holding onto one another's pedipalps, then rotating back and forth together with their tails (technically metasoma) raised above their backs. They sometimes bump their metasoma together without stinging, according to the San Diego Zoo, in a behavior called "clubbing."

The dance may last anywhere from minutes to hours. At the end of the dance, the male deposits his spermatophore on the ground for the female, then leaves.

4. They Give Birth to Live Young

A cluster of baby scorpions cling to their mother's back.
A cluster of baby scorpions cling to their mother's back. Oil and Milk / Getty Images

Unlike most arachnids (and most other invertebrates in general), scorpions are viviparous. That means they give birth to live young rather than laying external eggs. The babies may be born two to 18 months after mating, depending on the species, and look like adult scorpions only much smaller with a soft, white body. They quickly clamber onto their mother's back, who is known to fiercely defend them until it's time for them to move on.

5. Some Baby Scorpions Stay With Their Mom for 2 Years

In many scorpion species, the babies absorb a nutritious yolk sac while on their mother's back, then leave a few days later after their first molt. In some cases, though, the mother kills prey to feed to her babies, who might stay in her care for as long as for two years.

6. They Glow In UV Light

A giant hairy scorpion (Hadrurus arizonensis) glows blue under UV light.
A giant hairy scorpion (Hadrurus arizonensis) glows blue under UV light. Joshua Tree National Park / Flickr / public domain

Adult scorpions have fluorescent chemicals in their hyaline layer, part of the cuticle in their exoskeleton, that cause them to glow under ultraviolet light. Scientists aren't entirely sure what evolutionary advantage this offers scorpions, but theories include helping protect them from sunlight, helping them locate each other, or helping them hunt.

For humans, however, this quirk makes it much easier to find otherwise elusive scorpions. It's a big benefit for researchers trying to study them, for example, as well as for hikers and campers trying to avoid them. And the hyaline layer is impressively durable, since scorpion fossils often still glow under UV light even after millions of years.

7. Some Scorpions Can Go a Year Without Food

Scorpions primarily prey on insects and spiders, but some larger species may also take small lizards or mice. Some are ambush predators, some actively hunt for prey, and some even set pitfall traps. However they get their food, though, they can only eat it in liquid form, so they use enzymes to digest their prey externally, then suck it into their tiny mouths.

Thanks to low metabolic rates, many scorpions can survive long periods between meals. They often feed every couple of weeks, but in some cases, they're known to go six to 12 months without eating.

8. Their Venom Can Include Dozens of Different Toxins

A three-keeled bark scorpion (Lychas tricarinatus) curls its metasoma at Udanti Tiger Reserve in Chhattisgarh, India.
A three-keeled bark scorpion (Lychas tricarinatus) curls its metasoma at Udanti Tiger Reserve in Chhattisgarh, India. ePhotocorp / Getty Images

All scorpions have venom, but that venom is diverse and complex. Of 1,500 known species, only about 25 are thought to be capable of killing humans. Still, that 2% of species can pose a serious threat to human life in some parts of the world, especially where medical treatment is difficult to access. The deathstalker of North Africa and the Middle East is often cited as one of the deadliest scorpion species on Earth, along with the Indian red scorpion and the Arabian fat-tailed scorpion.

A single scorpion may produce venom with dozens of individual toxins, including neurotoxins, cardiotoxins, nephrotoxins, and hemolytic toxins, as well as a wide variety of other chemicals like histamine, serotonin, and tryptophan. Some toxins are more effective on certain kinds of animals, such as insects or vertebrates. Scorpions use their venom both to subdue prey and to protect themselves from predators, which range from centipedes to birds, lizards, and small mammals.

9. They're Stingy With Their Stingers

Scorpions can control whether and how much venom to release with a sting, and given the energy required from their bodies to produce such complex venom, they tend to be conservative with it. They will often kill prey with their pincers if possible, resorting to venom only when necessary.

10. Their Venom Can Kill — or Save Lives

The deathstalker scorpion (Leiurus quinquestriatus)
The deathstalker (Leiurus quinquestriatus) is one of the most dangerous scorpions on Earth, but a chemical in its venom has also inspired research into new cancer treatments. מינוזיג / Wikimedia Commons / CC BY-SA 4.0

Despite the potential dangers of scorpion venom, research has also revealed lots of helpful compounds hiding in there. Chemicals in scorpion venom have already proven to be a font for medical biomimicry, and countless more are waiting to be discovered.

Deathstalker venom includes chlorotoxin, for example, which has inspired new methods for both diagnosing and treating certain cancers. Venom from the lesser Asian scorpion has antimicrobial peptides that may be effective against many bacteria and fungi as well as malaria parasites, along with anti-inflammatory properties that could make it an effective treatment for arthritis.  Other scorpion-venom compounds have also shown promise as immunosuppressants for the treatment of autoimmune disorders.

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