Spiders and Scorpions - More ArthropodsSpiders are also arthropods. Arthropods are a big group of creatures. We divided up our pages because the creatures come in such a variety. You would never confuse a tarantula, lobster and a butterfly, but they all have similarities.
Arthropod ReviewSpiders are close to insects, but still very different. Like all arthropods, they have jointed legs and segments for their main body. To keep those legs and segments moving properly, arthropods also have nervous systems that are very advanced. What else? Many arthropods also have an exoskeleton. The exoskeleton is the hard outer shell. If you touch an insect, spider or crab you'll find it to be hard. If you look at a mammal, they are usually soft. If they aren't, their protection is a specialized piece of their skin (the skeleton is on the inside). But what makes these guys different?
Spiders, Scorpions, and Horseshoe Crabs... Oh My!Ah yes... The subphylum Cheliceriformes. There are a lot of them. Over 70 thousand species. The big thing that sets them apart is the number of legs. Eight (8). Most of you probably know that spiders have eight legs. So do scorpions and horseshoe crabs. They usually don't have antennae either. They have complex eyes so they can find prey. Did we mention that many of the members of this subphylum are predators? We should.
While you might find spiders in many locations around your house, scorpions are a little harder to find. Horseshoe Crabs are even more difficult to see. Horseshoe Crabs live in the ocean. You might find spiders and scorpions near the water, but they are not fond of living in the water. Some spiders can actually walk on water to capture their prey. It's a whole surface tension thing to keep them on top.
Spiders have the ability to live in almost any environment while you will usually find scorpions in dry areas. We just saw a spider in our offices this morning. But here in California, we have many scorpion species found across or deserts and grasslands. We haven't seen a scorpion in our offices. Thank goodness.
Science Nation: Got Silk? (NASA Video)
Encyclopædia Britannica (Spider):
Encyclopædia Britannica (Scorpion):