European wolf spiders found near the Italian city of Taranto were the first to be called tarantulas. Their venom doesn't affect humans, but from the 11th century into the 17th, people thought it caused a form of mania called tarantism that could be calmed only by a frenzied dance called the tarantella. "Tarantula" now generally refers to members of Theraphosidae, a family of about 900 species worldwide.
VENOM: Most tarantula venom doesn't affect humans, and doesn't contain the toxin that can cause anaphylactic shock when people are stung by bees or wasps. A few species from Australia and India have bites more dangerous to people.
HAIRY DANGER: American tarantulas' hair is more dangerous to people than their bites. Part of their fuzz is called "urticating hairs" because they can cause hives. If the hairs get into a small mammal's nose and throat, the swelling can asphyxiate the animal. People who get them in their eyes may need surgery to remove them.
BIG AND SMALL: The biggest U.S. tarantulas can have bodies up to 4 inches long, with an 8 inch spread from forefeet to hind feet. The smallest "can sit very comfortably within the circumference of a quarter," says biologist Chris Hamilton.
WHERE THEY LIVE: U.S. tarantulas all live west of the Mississippi River, in Arizona, California, Colorado, Kansas, Oklahoma, Missouri, Arkansas, Louisiana, Nevada, Utah, New Mexico and Texas.
SPIDER SEX: The short arm- or antenna-like appendages on each side of a spider's head are called "palps" or "pedipalps." Male spiders use them to transfer sperm to a female's body.
Interview with Chris Hamilton
Scientific paper: http://zookeys.pensoft.net/articles.php?id=6264
Arizona-Sonora Desert Museum: https://www.desertmuseum.org/kids/oz/long-fact-sheets/tarantula.php
Burke Museum: http://www.burkemuseum.org/blog/myth-tarantulas-are-dangerous-humans
National Wildlife Federation: https://www.nwf.org/Wildlife/Wildlife-Library/Invertebrates/Tarantulas.aspx
San Diego Zoo: http://animals.sandiegozoo.org/animals/tarantula
Tarantulas as pets: http://blogs.cornell.edu/spiders/tarantulas-terrible-or-terrific/
Encyclopedia Brittanica: http://www.britannica.com/art/tarantella