Have you ever been on a walk with a friend, and you pass a big spider sitting in the center of a web? Maybe you express alarm that it is so hefty, but your friend says, "Oh that? Just a banana spider — nothing to worry about."
While this assurance might be encouraging, it's basically inaccurate. Your friend might, in fact, know for certain that that particular arachnid — black and yellow, sitting in the middle of a giant web that has a zig-zag in it that looks as if it's made of dental floss (see picture below) — will not hurt you. However, it's definitely not true that every species on Earth commonly called a "banana spider" is harmless, so you shouldn't go around spreading that good news.
Here is where we run into the problem with common names.
Carl Linnaeus and Scientific Naming
Every life form on this planet that humans "officially" (meaning scientifically) know about — from animals to archaea — has a scientific name. Some of them also have one or 14 common names as well. The process by which the scientific establishment names living things was developed by a Swedish botanist named Carl Linnaeus in the 18th century. Linneaus created a double naming convention, and figured out how to organize living things into categories that made sense based on their form, structure and habits. Linneaus was very organized.
The process by which the rest of us collectively come up with common names isn't Linneaan in the least — it involves one person thinking that spider over there looks like it has a banana pattern on it and telling their buddies, and before too long, everybody's calling that animal a "banana spider." It's not a very precise way to name something, but common names have been around much, much longer than scientific names, and we still use them every day. For instance, If you went around referring to horses as Equus caballus, people would make fun of you. But sticking to common names can get really confusing, fast: When you're talking about a black bear, a scientist would want to know whether you were referring to American black bear (Ursus americanus) or the Asian black bear (Ursus thibetanus) — two members of the family Ursidae, which live on different continents. Context can help in figuring out which organism somebody's talking about — if you saw that black bear in Alaska, you could be pretty sure it was the species Ursus americanus — but not always, especially when you enter the kooky, confusing world of spider taxonomy.
"Common names can be tricky because people from different parts of the country or world will use the same common name to describe different species," says Kristie Reddick, founder of The Bug Chicks, an educational company that uses arthropods to teach young people about social issues like prejudice, racism, educational potential and personal development. "Case in point — the potato bug. Where I'm from in Virginia, the name 'potato bug' refers to an isopod that most people know as a roly-poly. But in the western U.S., potato bugs refer to Jerusalem crickets, which is a kind of ground cricket with big jaws and the head of a demon baby. You can totally hold an isopod, but Jerusalem crickets can bite. Common names can mess up our communication and mess up identification of organisms."
So, back to the banana spider. When your friend says, "Don't freak out, it's just a banana spider!", what is she actually talking about? And is she right?
A few species commonly called "banana spider" are, in fact, harmless. The yellow and black Argiope spiders that can be found all over the contiguous United States (they're the one that puts a signature zig-zag in the middle of their webs) are often called a banana spider or garden spider. While it has venom like all spiders, it doesn't cause much of a reaction in humans. Also common in North America are members of the Nephila genus, which have cylindrical bodies. These are commonly called banana spiders, golden silk spiders, writing spiders or calico spiders, and their venom is largely harmless to humans as well, although some species have large fangs, so if they do have occasion to bite you, it might hurt like any other puncture wound.
But not everything we refer to as a "banana spider" is harmless.
The Brazilian Wandering Spider
"When I think of banana spiders, I think of the Brazilian Wandering Spider in the genus Phoneutria," says Reddick. "My grandfather was bitten by one when he was a dock worker in New York City. He was unloading bananas from South America when he was bitten. It was apparently so painful that it became a part of our family storytelling legends."
Phoneutria, whose name comes from the Greek word for "murderess," is extravagantly toxic, packing enough venom to kill a small child. Called "banana spiders" because they are sometimes found in banana shipments from South America, these hairy, brown arachnids don't build webs, but hunt their prey like little jaguars. If you're bitten by one (which is unlikely unless you live in South America or are working in the banana import business), it's best to seek medical help ASAP.
The Goblin Spider, Genus Bannana
And to make things more complicated, the scientific name of one goblin spider genus is Bannana. These are extremely small (around 1 or 2 millimeters in length), live in the leaf litter in the high rainforests of China, and have hardly any eyes. Scientists are uncertain whether they have much in the way of venom, but it's extremely unlikely you'll ever find out.
But, according to Reddick, your friend who told you not to worry about that spider is probably right in one way:
"I think no matter what, it's important to understand that spiders — banana or not — are not out to get you."
And it's fine to use common names — it's just important to clarify and explain exactly what you're talking about if there is any danger of confusion.