Are spiders and tarantulas insects?

Mexican Red-kneed Tarantula
Image credit: George Chernilevsky

No!  They are arachnids.  Scorpions, mites and ticks are considered as family members. Many people think spiders are insects but they are mistaken as insects have six legs and three main body parts.  Scientists suggest there are over 75,000 species of arachnids, the majority of them spiders.

Wolf Spider
Image credit: Philip N. Cohen

What are arachnids anyway?  They are creatures with two body segments, eight legs, no wings or antennae and are not able to chew.  Many arachnids use silk, either to catch prey or to help them reproduce.  Most can only eat liquid food, so they squirt digestive chemicals into their prey and suck out the juice.  They are predators on insects and other invertebrates, except for many mites which feed on all kinds of things, like fungus, plants, dead animals, bacteria and other invertebrates.

Dew covered spider web
Image credit: Rosendahl

Tarantulas are a type of spider but are somewhat different from most spiders.  So, what’s the difference between them?

• Tarantulas are usually larger than most spiders.

• Not all spiders are hairy-bodied, whereas tarantulas are always.

• Tarantulas have two or four spinnerets (silk exuding tube-like structures) while spiders have six.

• Spiders exude silk to make webs to capture prey, whereas tarantulas do that for carpeting of floor of the nest and make hammock-like bedding for resting.

• Silk producing glands in the feet are unique for the tarantulas.

• Presence of barbs on the fleshy abdomen is a distinguishing feature of tarantulas.

• The lifespan for tarantulas is very high compared to spiders.

Why don’t you catch a spider and examine how it looks like?  Make sure you handle it with care and return it to where you got it from.  Forget about tarantulas.. they are DANGEROUS!

Sign up for the 'Spiders & Tarantula' interactive sessions happening during Petrosains Science Festival from 15-21 September 2014. Get your tickets at www.sciencefestival.my NOW! #petrosainsfest

Shared by Azni

Learning Specialist, Petrosains