Welcome to Arachnopedia!

Looking for spiders on the web? You found them!

Arachnopedia is an independently-spun website made by a spider enthusiast to compile information about different species of spiders. It's an ongoing project, and still quite a new one, but in the future, I hope to help people learn about some of the world's most misunderstood animals. Please enjoy your stay here.

News

March 14, 2024
Hello! Welcome to Arachnopedia. This website is still quite new, so there’s not much yet in the way of news, but in the future, I plan to use this section of the website to keep users updated on any changes I make to the site. Currently, I’m still working on setting up the basic “skeleton” of the website, so a lot of links on here will redirect to my “Site Under Construction” page until further notice.
- Annabelle Cane

Understanding Spiders - The Basics:

What makes an animal a spider?

When trying to understand what actually counts as a spider, it helps to consider how spiders are categorized taxonomically. Within the animal kingdom is the phylum Arthropoda, whose members are distinguished by the following characteristics:

They have a jointed exoskeleton made of chitin bound to protein.
Arthropods lack locomotory cilia, even in their larval stages. [Note: Cilia are short eyelash-like filaments present on the surface of most animals’ tissue cells. They facilitate locomotion (movement) of cells in order to achieve a variety of functions (which vary among different species)].
Arthropods usually have segmented bodies with a pair of jointed appendages attached to each segment.

This phylum is further divided into four subphyla: Myriapoda, Crustacea, Hexapoda, and Chelicerata. Of these, the one we’re interested in is Chelicerata. These are arthropods which have the following characteristics:

Their bodies are divided into a cephalothorax (the “head”) and abdomen (the “butt”).
They lack antennae.
They have a pair of chelicerae (mouthparts) and a pair of pedipalps (short limbs next to the chelicerae).
They have 8 legs, divided into 4 pairs, which they use to walk.

At this point, we are starting to get quite close what we understand as a spider. However, there are other chelicerates, like scorpions and horseshoe crabs, which are not spiders. So, we need to narrow our definition even further to get to an exact definition for a spider. Chelicerata can be divided into the classes Xiphosura (horseshoe crabs), Eurypterida (sea scorpions, now extinct), and Arachnida. Land-dwelling chelicerates like spiders and scorpions fall under Arachnida. Finally, within Arachnida is the order Araneae, whose members are known as spiders, defined by the American Arachnological Society as “air-breathing arthropods that have eight legs and chelicerae with fangs able to inject venom.”

Anatomy of a spider