How Old Are Spiders? Unveiling Earth’s Oldest Creepy Crawly

Spiders are one of the most fascinating and commonly feared creatures on earth. Although they are seen almost everywhere, little do we know about their age and evolutionary history. Have you ever wondered how old spiders are, and where they come from? In this article, we will dive deep into the spider’s history, their evolution and development, and answer some of the most commonly asked questions about these creepy crawlies.

The Age of Spiders

The existence of spiders on earth dates back to around 380 million years ago during the Devonian period. However, the first true spiders – the Araneomorphae and the Mygalomorphae, known collectively as the “true spiders” – emerged some 230 million years ago in the Mesozoic Era. But, when did the first spiders appear and how did they evolve? Let’s find out.

Spiders – Arachnids or Hexapods?

The origin of spiders has been a topic of intense debate for many years. Scientists have been uncertain whether spiders belong to the arachnid or hexapod groups. The hexapods are insects, and arachnids have two more leg pairs than the insects, making them an entirely different group. However, a recent study published in the Journal of Palaeontology has convincingly distinguished spiders as significant members of the arachnid group. The study states that the first true spiders were arachnid-like animals, perhaps even scorpion relatives that evolved to have six legs instead of eight, followed by their migration to a hairier appearance with some developing venom.

Evolution of Spiders

Spiders belong to the class Arachnida, which also includes other arthropods such as scorpions, ticks, mites, and harvestmen. Here’s a quick overview of spider’s Evolution:

The First Spiders

The first-known spiders were tiny creatures measuring just 1-2 mm, with elongated abdomens and short legs. They were discovered in Scotland’s Rhynie Chert, a rock formation created over 400 million years ago in the Devonian period. The discovery cemented that spiders have been around for more than 380 million years.

Mygalomorphae vs. Araneomorphae

Until the discovery of the Rhynie fossil, the oldest known spiders were the mygalomorphs – commonly known as tarantulas. These spiders have characteristic fangs that extend forward when the spider is ready to attack its prey. The Araneomorphae, including the orb-weavers, jumping spiders, and wolf spiders, did not appear until much later in the Mesozoic Era, around 200 million years ago. While both the mygalomorphs and Araneomorphae are part of the Arachnida class, they evolved different lifestyles and behaviors.

Spider Anatomy

Two of the defining features of the spider anatomic structure are the cephalothorax and the abdomen. The cephalothorax houses the spider’s brain, eyes, fangs, and other vital body systems, whereas the abdomen is responsible for the spider’s digestion, respiration, and reproduction.

The Cephalothorax and the Feeders

A spider’s cephalothorax consists of two parts— the cephalic region and the thoracic region. The cephalic region contains the eyes, brain, and feeding structures. The feeding structures include the fangs, pedipalps, and chelicerae—a bulb-shaped structure that releases venom. The pedipalps are appendages located on the sides of the cephalothorax mostly used for food manipulation, sensing, and mating.

The Abdomen and the Respiratory System

The abdomen is the larger section of a spider’s body responsible for the respiratory and digestive systems. Unlike some other arachnids, spiders do not have lungs. Instead, they use a gas exchange system called “book lungs.” The book lungs comprise layers of thin plates where the spider pumps fresh air in and removes CO2.

Spider Reproduction and Life Cycle

Spiders have a unique life cycle that involves multiple molts before reaching the adult stage. The length of this development process can differ depending on the spider species and their habitat. For example, some tropical spiders reach maturity in a year, while others could take up to three years to mature.

Spider Egg-laying and Hatching

Spiders are oviparous, which means they lay eggs to reproduce. After mating, the female spider lays eggs in a sac, often covered in silk. Depending on the species, the spiderlings emerge from the sac and go through several molts before reaching full maturity. Spiderlings hatch in clusters, and some spider mothers tend to them until they start to feed themselves.

Spiders and Humans

Humans tend to fear spiders and other creepy crawlies, but these creatures serve several ecological roles like pollinating plants and reducing bug populations. Unfortunately, some spiders are venomous and can pose a threat to humans. Here are some frequently asked questions about spiders and their impact on humans.

Do All Spiders Bite?

No, not all spiders bite. Most spiders use venom to capture prey and defend themselves. However, some spider species have non-toxic venom that does not harm humans or pets.

Are Spiders Harmful to Humans?

Out of over 45,000 spider species worldwide, only a few spiders pose a threat to humans. These spiders include the black widow, brown recluse, and funnel weaver spiders, which are all venomous. Their bites can cause skin reactions, muscle pain, and other health complications in humans. However, most spider species do not pose a threat to humans and can go their entire lives without biting.

What Can You Do to Prevent Spider Bites?

To avoid spider bites, ensure you shake out shoes and clothing before wearing them in areas where spiders are common. Sealing your home’s cracks and crevices, using screens on windows and doors, and keeping your home clean and free of clutter can also help prevent spider infestations.

Conclusion

Spiders are ancient creatures that have coexisted with other creatures on earth for millions of years. They play an essential ecological role and provide many benefits to humans, such as reducing the population of unwanted pests in homes and gardens. Although their presence may be intimidating, spiders are relatively harmless and are not aggressive towards humans. With a better understanding of these creepy crawlies, we can coexist and appreciate their unique features.

References

FAQs

  • Q. When did the first true spiders emerge?
  • A. The first true spiders – the Araneomorphae and the Mygalomorphae, known collectively as the “true spiders” – emerged some 230 million years ago in the Mesozoic Era.

  • Q. Are all spiders venomous?
  • A. No, not all spiders are venomous. Most spiders use venom to capture prey and defend themselves. However, some spider species have non-toxic venom that does not harm humans or pets.

  • Q. What can you do to prevent spider bites?
  • A. To avoid spider bites, ensure you shake out shoes and clothing before wearing them in areas where spiders are common. Sealing your home’s cracks and crevices, using screens on windows and doors, and keeping your home clean and free of clutter can also help prevent spider infestations.

  • Q. Are spiders harmful to humans?
  • A. Out of over 45,000 spider species worldwide, only a few spiders pose a threat to humans. These spiders include the black widow, brown recluse, and funnel weaver spiders, which are all venomous. Their bites can cause skin reactions, muscle pain, and other health complications in humans. However, most spider species do not pose a threat to humans and can go their entire lives without biting.

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