vividly-colored spider the size of your palm is rapidly spreading in parts of the U. The scientists (harmlessly) blew puffs of air on 16 Joro spiders and over 30 individuals of other species — as well as analyzing nearly 400 previous observations from other arachnid tests. If you're so inclined, Davis suggested even using a Joro in your backyard or front porch to observe, visit, and learn more about spiders