Tarantulas- cooler than you may think!

​Tarantulas

By Courtney Sweet

A deeper dive into anatomy, biology and evolution.

Objectives

• Identify the two main body regions of a tarantula.

• Describe how tarantulas use vibrations and specialized hairs to "see" their world.

• Explain the evolution of tarantulas from "Old World" ancestors to "New World" specialists.

• Understand the biological process of molting and why post-molt care is vital.

• Link tarantula anatomy to safe cleaning and handling practices.

The Evolution of the "Ancient Spider"

• Mygalomorphs: Tarantulas belong to an ancient group of spiders that has changed very little in 300 million years (older than many dinosaurs!).

• The Big Split: * Old World (Africa/Asia/Europe): These are the "Originals." They rely on speed and potent venom because they never evolved the "itchy" defense hairs.

  • New World (The Americas): These evolved later. They developed urticating hairs as a way to deter mammals without having to use their venom.

• The Fangs: Tarantulas are "Orthognathous." This is an ancient trait where fangs move up and down, rather than pinching together like "modern" spiders.

Multiple Choice

Which of these are a new world adaptation?

• Poisonous fangs

• Urticating hair

• Extra Legs

• 2 additional eyes

Multiple Choice

Which Tarantula relies on potent venom and speed to survive?

• Old world

• New world

• Both

• None

The Spider Layout-Two Body Parts (Not Three!)

• The Prosoma (Cephalothorax): The front section. Holds the brain, stomach, and legs.

• The Opisthosoma (Abdomen): The back section. Holds the heart, lungs, and silk tools.

• The Pedicel: A tiny "waist" that connects the two parts.

The Engine Room (The Prosoma)

What's inside the front half?

​Leg Attachment: All 8 walking legs are attached here.

Sucking Stomach: Spiders can't chew! They pump liquid into their stomach like a vacuum.

The Brain: Controls movement and basic instincts (Eat, Hide, Molt).

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Happy teaching!

The Storage Center (The Abdomen)

• Book Lungs: Spiders breathe through slits on their belly. They look like the pages of a book.

• The Heart: A long tube that pumps clear "blood" (Hemolymph).

• Spinnerets: Two to four finger-like organs that "knit" silk.

  The abdomen is very fragile. If a tarantula falls from a height, this part can "pop," which is why we handle them very carefully.

​What's inside the back half?

The "Extra" Legs (Pedipalps)

• Tarantulas look like they have 10 legs.

• The front two are Pedipalps.

• They use them like hands to move food, feel the ground, and help them climb.

Seeing With Feet (The Super Sense)

• If they can't see, how do they hunt? Vibration.

• Slit Sensilla: Tiny organs in their "knees" that feel the weight of a cricket landing 2 feet away.

• They are so sensitive they can feel the "heartbeat" of prey.

Eyes, But No Sight?

• Tarantulas have 8 eyes on top of their head.

• The Reality: They are legally blind!

• They can only see light, dark, and movement. They can't watch TV or recognize your face.

Setae - More Than Just Hair

• Tarantulas are covered in hairs called Setae.

• Some hairs "smell" chemicals.

• Some hairs "hear" air moving (like a bird’s wing).

• Trichobothria: Very long hairs that detect the tiniest breeze.

Fangs and Chelicerae

• The Chelicerae are the "jaws."

• Inside are the Fangs.

• Tarantula fangs move up and down (Old World/Primitive style).

• Most garden spiders' fangs move side-to-side like pincers.

Secret Weapons: Itchy Hairs

• Urticating Hairs: Only New World (Americas) spiders have these.

• When scared, they kick these hairs off their bum.

• They have tiny barbs (like hooks) that get stuck in an attacker's eyes or nose. It’s like being hit with fiberglass!

Molting: The Great Escape

• Step 1: The spider stops eating and turns dark.

• Step 2: It flips onto its back (it’s not dead, just busy!).

• Step 3: The old skin pops open, and the spider crawls out.

Post-Molt Care

• After molting, the spider is soft and white.

• Safety Risk: Even a cricket can kill a spider during this time!

• Rule: Never feed or handle a spider for at least 7–10 days after a molt until the fangs turn black and hard again.

Multiple Choice

How many body parts does a tarantula have?

• 2

• 3

• 5

• 1

Multiple Choice

What do tarantulas use to feel vibrations?

• Setae (Hair)

• Smell receptors

• Simple auditory signals.
• Webs

Multiple Choice

Why do they flip on their back?

• They flip on their back to exercise, explore, or avoid predators.
• They flip on their back to attract mates, mark territory, or signal distress.
• They flip on their back to find food, sleep, or escape danger.
• They flip on their back molt

They are not scary.... just sensitive!

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Tarantulas