Common Arachnids Of The Rocky Mountains

common arachnids

Look at those long legs!

Do you know all of these common arachnids of the Rocky Mountains?  Some of them are dreaded and feared, but others are little known or ignored.

There are all kinds of arachnids that live in the Rocky Mountains.  You can find them on the ground, in trees, or under rocks.  I have actually seen most of them inside my house at one point or another.  Without further ado, here are some of the common arachnids that you are likely to encounter in the Rocky Mountains.

What Is An Arachnid?

An arachnid is a class of invertebrate animals that have eight jointed legs, two body parts, and an exoskeleton.  There are over 70,000 species within this class of animal.

The majority of these animals are spiders.  However, there are also scorpions, ticks, and harvestmen.

Common Arachnids Of The Rocky Mountains

common arachnids

A black and yellow garden spider.  Photo via Flickr.

Black and Yellow Garden Spider

This is a common spider that is often seen in gardens or shrubby meadows and is on the larger side at about 1 inch.  It’s main feature is a large black and yellow abdomen.

It often forms a large web with a central zig zag pattern in plants in sunny, sheltered areas.

common arachnids

A black widow.

Black Widow

The famous and dreaded black widow spider is in fact poisonous.  It is the most poisonous spider in North America.  Luckily though, it is generally not fatal to adults, but it can kill children or the elderly.

They have a very distinctive red hour glass shape on the underside of their black body.

Daddy Longlegs

This spider has an oval body that is about 1/4 inch.  The legs are very long and distinctive.  It is usually seen alone, but sometimes it can be seen in a mass with many others.  This spider is nonvenomous.  You can read this old post about daddy longlegs here.

common arachnids

A Rocky Mountain wood tick. Photo via Flickr.

Rocky Mountain Wood Tick

This is very small, only 1/8 inch.  It waits on grasses for passing mammals, which it attaches onto and feeds on.  It has only 3 meals in it’s lifetime – 2 on small mammals and the final one on a large mammal.  It can pass on some bad diseases, so be careful.  It is most often seen from June to September.

common arachnids

A windscorpion.  Photo via Flickr.


This is not actually a scorpion, but a spider that looks very similar to a scorpion.  It is about 1 1/4 inches big with a pointed head and large abdomen.  It is a very fast runner.   This is not venomous.