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. In the 18th century, a Swedish botanist named Carl Linnaeus developed this process of naming living things.
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 a very organized Swede, and his solution became the standard for scientific taxonomy.
The process by which the rest of us collectively come up with common names isn't Linneaan in the least. It often involves one person thinking that spider species 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. 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 really 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 U. americanus -- but not always, especially when you enter the kooky, confusing world of insect and 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."
Trichonephila clavipes (banana spiders) and A. aurantia are often confused for one another. T. clavipes has a slender, cylindrical abdomen, while the mature A. aurantia has a more rounded and somewhat flatter abdomen.
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?