What is a spider?
Most people think they know the answer to this question, but when challenged they usually say more about what a spider is not. Like, it’s not an insect, or not what you want to find in your lunch. So here’s my attempt to say what a spider really is.
Yep, that’s a spider. Or more specifically, a Golden Orb Weaver (Nephila ornata)
A spider is an eight-legged critter that eats other critters. Where the term ’spineless’ is considered a bit of an insult for humans, among spiders it invites a sense of belonging because they don’t have a spine at all. Instead, they carry their squishy bits around inside a hard armour-like skin called an exoskeleton.
Now, apart from the bit about having eight legs I could have been describing a lot of other critters, including several insects here, so I’ll now mention some more things that make them different from insects.
You’ll see in the cartoony pictures above that the spider doesn’t have wings. That means spiders can’t fly, although some of them do manage tricks which allow them to either glide or be carried by the wind. You’ll also see that the insect has its body divided into three main bits (head, thorax and abdomen) while the spider has only two bits. That’s because the spider’s head and thorax are combined into one section called a cephalothorax.
Not a spider: This little critter has eight legs like a spider, but it’s not a spider. My guess is it’s a Red Velvet Mite. This one was about 3 mm long. Mites are closely related to spiders.
And here’s another thing about spiders: they’re not able to chew their food.
A discarded Huntsman Spider skin in my hand
Another shot of the Huntsman Spider skin. This close-up detail shows the fangs
Outgrowing their skins
I mentioned earlier that spiders wear a tough skin called an exoskeleton to hold their soft bits together. That system works well for spiders but it has its limitations too. The exoskeleton is not able to keep expanding as the spider inside it gets bigger. So as a spider grows up it sometimes has to produce another skin and shed the old one. The picture at right shows the discarded skin of a Huntsman spider.
Discarded spider skins are more interesting than most people realise. If you look at the close-up picture alongside it you’ll see it’s covered with lots of stuff like hairs and spines. So the spider sheds a lot of stuff with that skin. Of course I made sure there wasn’t a spider wearing the skin before I picked it up. When you see the size of its fangs you’ll understand why.
The bits that bite
Spiders have fangs which can inject venom. Despite that fact, most spiders are not dangerous to people. However, because some spiders can be dangerous I advise people to treat all spiders with caution, especially if you have trouble knowing which ones are the most venomous.
Venomous or poisonous?
You might have noticed that I said that spiders inject venom from their fangs. That’s why spiders are described as venomous instead of poisonous.
Now I could get into a bit of trouble here because this subject is complicated, but a rough guide goes something like this: something is considered poisonous if it’s dangerous to eat it. For example, many types of wild mushrooms are poisonous.
And a critter is considered venomous if it puts venom into you by either biting or stinging.
Daddy-longlegs Spider
Bad reputation
Some of the spiders which have bad reputations don’t deserve them. For example, the Daddy-longlegs Spider (picture below) is sometimes claimed to have the deadliest venom in the world, and the story goes on to say that it’s unable to inject that venom into people because of its small fangs. Well I’ve been bitten by a Daddy-longlegs Spider and it sure didn’t kill me. So how did the story start?
I’ve heard a theory about how they got their bad reputation and it goes like this: Someone might have seen a Daddy-longlegs eating a Redback Spider. We know that Redbacks are dangerous, so therefore it was assumed that if it beat a Redback in a fight then it must be even more dangerous.
And that would be a great example of bad logic.
You see, when a Daddy-longlegs meets a Redback Spider it’s not an even contest. The Daddy-longlegs has an advantage over the Redback because it has longer legs. It can use those long legs to hold the Redback at a distance which prevents the Redback from biting it. So it has a pretty good chance at beating the Redback in a fight.
